Artículos de revistas: "Merino sheep Animal nutrition"

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Santiago, L. Lomas, D. Blache, M. A. Blackberry, G. B. Martin y A. B. Mâncio. "309. Nutrition, insulin, leptin and puberty in Merino ram lambs". Reproduction, Fertility and Development 17, n.º 9 (2005): 132. http://dx.doi.org/10.1071/srb05abs309.

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Merino sheep developed in Mediterranean regions so are well adapted to acute changes in food availability. However, restricted intake during pregnancy, especially in animals that are pregnant over the dry summer, could limit the positive effects of a winter rainy season on fetal development. In this study, we tested whether the level of nutrition during pregnancy and during pre-pubertal development affected blood concentrations of insulin and leptin, scrotal circumference and age of puberty in male Merino lambs fed with pasture. During dry weather, pregnant sheep were supplemented ad libitum with hay and lupin grain (Lupinus angustifolius) to compensate for decreases in pasture supply. Puberty was detected using a standardised behavioural test with oestrous ewes. Lambs were considered pubertal if they displayed mounting in two successive weekly tests. There were no differences in plasma concentrations of insulin or leptin. The values for both hormones simply displayed the same pattern, with a rise after feeding and a fall during non-feeding periods. There was no difference among treatments in either scrotal growth or age to puberty (Table 1). This might be because the dietary treatments, being administered by food restriction under field conditions, would not have the same effects as severe undernutrition that has been used in laboratory studies. Alternatively, Merino sheep may have a greater capacity to cope with mild nutritional stress.

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Martin, Graeme B., Soedjiharti Tjondronegoro, Rachid Boukhliq, Margaret A. Blackberry, Jan R. Briegel, Dominique Blache, James A. Fisher y Norman R. Adams. "Determinants of the annual pattern of reproduction in mature male Merino and Suffolk sheep: modification of endogenous rhythms by photoperiod". Reproduction, Fertility and Development 11, n.º 6 (1999): 355. http://dx.doi.org/10.1071/rd00005.

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In mediterranean environments, pastures are very poor during the autumn and consequently small ruminants, such as sheep, would have been losing body mass for many months so, during mating, gamete production would be depressed in both sexes. Effectively, the nutritive requirements for a photo-period-driven, annual reproductive cycle are out of phase with seasonal changes in food availability. The problem could be overcome through more flexible timing of reproduction, perhaps explaining variations in seasonality between breeds that originate from differing latitudes. To study these concepts and the mechanisms involved, the endogenous rhythms and responses to photoperiod were compared in rams of ‘mediterranean origin’ (Merino) and ‘temperate origin’ (Suffolk). Groups of 16 rams of each breed were given a constant food supply and subjected to 16 months of constant equinoctial photoperiod (12L : 12D) or simulated ‘mediterranean’ changes in daylength (from 14L : 10D to 14D : 10L). With nutritional and photoperiodic inputs held constant, Merino and Suffolk rams showed similar endogenous rhythms in reproductive activity. Under constant nutritional inputs and a mediterranean photoperiodic cycle, the endogenous rhythms were modified differently in the two breeds, with the Merinos starting and finishing their seasons about 2 months earlier than the Suffolks. These observations partially explain the patterns observed in rams kept under field conditions. It is now necessary to test whether the rhythms of reproduction in these breeds are also modified by changes in nutrition and social cues.

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Warner, R. D., D. W. Pethick, P. L. Greenwood, E. N. Ponnampalam, R. G. Banks y D. L. Hopkins. "Unravelling the complex interactions between genetics, animal age and nutrition as they impact on tissue deposition, muscle characteristics and quality of Australian sheep meat". Australian Journal of Experimental Agriculture 47, n.º 10 (2007): 1229. http://dx.doi.org/10.1071/ea07229.

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The combined effects of age and genetics and Poll Dorset sire and growth path were studied in two separate experiments (n = 595 and 627, respectively). In the first experiment, containing genotype crosses typically used in Australia (Merino, Poll Dorset, Border Leicester) and sires selected for growth or muscling, sheep were slaughtered at 4, 8, 14 and 22 months. The second experiment used Poll Dorset sires selected for high muscling, fat or growth with progeny having two levels of nutrition postweaning. Border Leicesters expressed higher levels of carcass fat percentage and intramuscular fat and produced the heaviest carcass. Merinos had the lowest subcutaneous fat depth and highest carcass lean percentage when compared at the same age. The progeny of Poll Dorset sires selected for high muscling (PDm) expressed a shift toward glycolytic fibres relative to those from Merino sires, and PDm sires produced progeny with reduced spine and limb length and higher carcass muscle : mineral ratios, suggesting skeletal stunting. Genotype meat quality differences were minimal except that PDm sire topsides were tougher and Merinos produced higher pH meat. With age (4–22 months), lambs became heavier and fatter, fibres shifted towards oxidative and away from glycolytic, muscle myoglobin increased, the meat became darker and redder and tenderness declined. Early weaning had no effect on the time to reach slaughter weight, provided nutrition was not restricted. The sire genetics influence on the carcass composition far outweighed the effect of nutrition postweaning. Lambs on a restricted diet tended to have less acceptable meat quality but this was not evident in lambs from sires selected for high fatness. Sensory tenderness was improved and intramuscular fat was higher in lamb progeny from sires selected for high fatness.

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Kelly, RW, I. Macleod, P. Hynd y J. Greeff. "Nutrition during fetal life alters annual wool production and quality in young Merino sheep". Australian Journal of Experimental Agriculture 36, n.º 3 (1996): 259. http://dx.doi.org/10.1071/ea9960259.

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The effect of maintenance v, submaintenance diets of pregnant ewes in 1991 and 1992 on establishment of the wool follicle population in their progeny, and its effect on the progeny's wool production (quantity, quality and variation across the body of the animal) to 1.4 years of age was examined. The experimental protocol used cloned animals created by bisecting embryos at day 6 of pregnancy. Each clone was placed in a ewe, which was subsequently fed from about day 50 to 140 of pregnancy at maintenance or submaintenance. Ewes on maintenance nutrition maintained liveweight throughout pregnancy, while submaintenance ewes were 12.1 kg lighter (P<0.001) 10 days before lambing. In 1991, a total of 74 lambs were born, including 17 sets of surviving clones. In 1992, 102 lambs were born, including 18 sets of surviving clones. Only data for the 35 sets of genetically identical 'twin' progeny and their dams are reported. Birth weights of lambs born to ewes fed at the submaintenance rate were 0.5 kg lighter (P<0.01) than their 'twins' born to ewes fed at maintenance. Midside secondary:primary (Sf: Pf) ratios for mature wool follicles were less (P<0.01) at birth, lamb and hogget shearing (1.4, 1.5 and 2.1 units respectively) for the progeny born to ewes fed at submaintenance. Progeny from ewes on the submaintenance treatment produced less clean wool, 0.1 kg to 0.4 years of age (P<0.01) and 0.14 kg between 0.4 and 1.4 years of age (P = 0.10), than their maintenance counterparts. Hogget wool was 0.1 pm broader (P<0.05), with a 0.5% units lower coefficient of variation of fibre diameter (P<0.01), and a position of break closer to the staple tip (P<0.001) for progeny of submaintenance ewes than their maintenance counterparts. There were no significant differences in yield, staple length, staple strength and percentage of fibres greater than 30 pm in diameter. Differences in mean fibre diameter arose between 1 and 1.4 years of age, coinciding with the period that the animals were grazing high quality pasture. Effects of maternal undernutrition on mean fibre diameter and Sf: Pf follicle ratios of progeny were most pronounced on the hind leg (P<0.01), and not significant on the front leg. However, variations in other wool quality traits across the body of the hoggets, expressed as a percentage of the midside value, were not significantly affected by maternal undernutrition. Clearly when evaluating management strategies for the pregnant ewe, the effect on lifetime production and quality of wool of their progeny needs to be considered. Merino hoggets that produce an extra 0.14 kg clean wool that is 0.1 pm finer will compensate for some extra management and feeding of their dams during pregnancy to prevent weight loss. If these effects continue throughout the life of the animal, then it will increase the cost effectiveness of feeding to maintain maternal weight over pregnancy.

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Coppock, D. L., J. E. Ellis y S. K. Waweru. "A comparative in vitro digestion trial using inocula of livestock from South Turkana and Kitale, Kenya". Journal of Agricultural Science 110, n.º 1 (febrero de 1988): 61–63. http://dx.doi.org/10.1017/s0021859600079697.

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SummaryThe dry-matter digestibilities of 13 important herbaceous and browse forages from an arid rangeland in north-western Kenya were evaluated in a comparative in vitro trial using rumen fluid from indigenous sheep, goats, a camel, and Merino sheep kept at an agricultural laboratory. All inoculum donors had varied diets preceding the experiment, but little substantial difference was observed in the ability of each fluid to digest test materials. Tt was concluded that the Merino sheep inoculum provided an adequate substitute for inocula from indigenous animals for studies of the nutritional ecology of free-ranging livestock.

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Paganoni, B. L., C. M. Oldham, M. B. Ferguson, A. N. Thompson, P. E. Vercoe y D. G. Gordon. "Ewe nutrition during pregnancy and birthweight of lambs has minimal impact on fat and eye muscle depth in Merino progeny". Animal Production Science 53, n.º 6 (2013): 509. http://dx.doi.org/10.1071/an12266.

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The hypothesis tested in this experiment was that Merino lambs with lower birthweights, due to poor ewe nutrition during pregnancy, would have more fat and less muscle than Merino lambs with higher birthweights. At two sites (Victoria and Western Australia) in each of 2 years, a wide range in the liveweight profiles of ewes was generated during pregnancy and lactation by varying the amount of supplements fed and feed on offer grazed. Progeny had fat and muscle depth at the C-site measured at various ages from 8 to 28 months of age. Across the four experiments, there were differences of 0.5 kg in birthweights and 8 kg in weaning weights between extreme treatments. The effects on the depth of fat and muscle were very small with fat depth increasing by 0.1–0.2 mm (5–7%) and muscle depth increasing by 0.2–0.7 mm (1–3%) when birthweights decreased by 1 kg. The effects of birthweight on fat depth are consistent with our hypothesis whereas the effects of birthweight on muscle depth are in contrast to our hypothesis. Nevertheless, the impacts of birthweight on the depth of fat and muscle measured at the C-site of progeny from Merino ewes, is unlikely to be of any commercial significance within the range of nutritional scenarios during pregnancy and lactation that are likely to be experienced within the Australian sheep industry.

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Liu, S. M., T. L. Smith, D. G. Palmer, L. J. E. Karlsson, R. B. Besier y J. C. Greeff. "Biochemical differences in Merino sheep selected for resistance against gastro-intestinal nematodes and genetic and nutritional effects on faecal worm egg output". Animal Science 81, n.º 1 (agosto de 2005): 149–57. http://dx.doi.org/10.1079/asc50180149.

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AbstractThe faecal egg count (FEC) and total egg output is reduced in parasite-resistant sheep and breeding sheep for resistance should reduce infective larval contamination of pastures. This research compares lambs and rams from the parasite-resistant flock, Rylington Merinos, with unselected controls at the same level of larval challenge and the same level of food supply in an animal-house environment. The sheep were penned individually. The parasite resistant sheep excreted 0·85-fold less eggs than the control animals after infection with Trichostrongylus colubriformis and Ostertagia circumcincta for 12 or 18 weeks. During the infection period the parasite resistant lambs had higher plasma immunoglobulin concentration and higher ratio of globulin to albumin than the control animals. In the mature rams these genotype differences diminished. They also had lighter mass of the small intestine with a higher proportion of mucosa, but heavier mass of the large intestine. Parasite infection caused a depletion of blood glutathione in the lambs given food at maintenance or 1·5 × maintenance, and the parasite-resistant sheep (both lambs and rams) also had lower glutathione concentration. Maintaining good body nutrient reserve before the infection reduced the egg output in the early stage of the infection. Food intake had little effect on worm egg production in young sheep given food at maintenance or above. It is suggested that an improvement of nutrition, sulphur-containing amino acids in particular, is required to recover the loss of productive performance caused by the infection.

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Searle, T. W., N. McC Graham y J. B. Donnelly. "Change of skeletal dimensions during growth in sheep: the effect of nutrition". Journal of Agricultural Science 112, n.º 3 (junio de 1989): 321–27. http://dx.doi.org/10.1017/s0021859600085774.

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SummaryMeasurements of skeletal size were made at 2–3-month intervals on 30 Border Leicester × Merino castrate male (wether) sheep between 2 and 27 months of age. Fifteen sheep were fed ad libitum on a high-quality diet and the other 15 half the average amount consumed by the first group, age for age. The ad libitum group grew faster and were larger in all body dimensions on each occasion, except for leg length at 27 months which showed no statistical difference between groups. When the groups were compared over the live-weight range common to both (16–44 kg) the unrationed animals were consistently wider at the shoulders but smaller in leg and chest dimensions.The relationship between each body component and age is described by a Mitscherlich equation and the relationship with live weight by a linear equation in which both variables are log transformed. Separate relationships were determined for each sheep and tested for differences within and between groups.

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Mortimer, S. I., J. H. J. van der Werf, R. H. Jacob, D. W. Pethick, K. L. Pearce, R. D. Warner, G. H. Geesink et al. "Preliminary estimates of genetic parameters for carcass and meat quality traits in Australian sheep". Animal Production Science 50, n.º 12 (2010): 1135. http://dx.doi.org/10.1071/an10126.

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Using performance from progeny born in 2007 and 2008 generated by the Information Nucleus program of the Cooperative Research Centre for Sheep Industry Innovation, preliminary estimates of heritability were obtained for a range of novel carcass and meat attributes of lamb relevant to consumers, including carcass characteristics, meat quality and nutritional value of lamb. Phenotypic and genetic correlations of live animal traits with carcass composition and meat quality traits were also estimated. The data were from progeny located at eight sites, sired by 183 rams from Merino, maternal and terminal meat breeds and were representative of the Merino, Border Leicester × Merino, Terminal × Merino and Terminal × Border Leicester-Merino production types of the Australian sheep industry. Data were available from 7176 lambs for weaning weight, 6771 lambs for ultrasound scanning and 4110 lambs for slaughter traits. For the novel meat quality traits, generally moderate to high heritability estimates were obtained for meat quality measures of shear force (0.27 aged 1 day, 0.38 aged 5 days), intramuscular fat (0.39), retail meat colour (range of 0.09 to 0.44) and myoglobin content (0.22). The nutritional value traits of omega-3 fatty acids and iron and zinc contents tended to have low to moderate heritabilities (0.11–0.37), although these were based on fewer records. Fresh meat colour traits were of low to moderate heritability (0.06–0.21) whereas measures of meat pH were of low heritability (~0.10). For the carcass traits, estimates of heritability were moderate to high for the various measures of carcass fat (0.18–0.50), muscle weight (0.22–0.35), meat yield (0.24–0.35), carcass muscle dimensions (0.25–0.34) and bone weight (0.27). Results indicate that for most lamb carcass and meat quality traits there is sufficient genetic variation for selection to alter successfully these characteristics. Additionally, most genetic correlations of live animal assessments of bodyweight, muscle and subcutaneous fat with the carcass and meat quality traits were favourable. Appropriate definition of breeding objectives and design of selection indexes should be able to account for the small unfavourable relationships that exist and achieve the desired outcomes from breeding programs.

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Kilminster, Tanya F. y Johan C. Greeff. "A note on the reproductive performance of Damara, Dorper and Merino sheep under optimum management and nutrition for Merino ewes in the eastern wheatbelt of Western Australia". Tropical Animal Health and Production 43, n.º 7 (2 de julio de 2011): 1459–64. http://dx.doi.org/10.1007/s11250-011-9871-8.

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Martin, Graeme B., Maria J. Hötzel, Dominique Blache, Stephen W. Walkden-Brown, Margaret A. Blackberry, Rachid Boukhliq, James S. Fisher y David W. Miller. "Determinants of the annual pattern of reproduction in mature male Merino and Suffolk sheep: modification of responses to photoperiod by an annual cycle in food supply". Reproduction, Fertility and Development 14, n.º 3 (2002): 165. http://dx.doi.org/10.1071/rd02010.

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Rams of a 'Mediterranean breed' (Merino) and a 'temperate breed' (Suffolk) were compared to determine how much of the differences between their reproductive seasons is owing to variation in their responses to photoperiodic and nutritional cues. In a previous study, both nutritional and photoperiodic inputs were held constant, and it was found that the two breeds show similar endogenous rhythms and, when the animals are challenged with a Mediterranean photoperiodic cycle, these endogenous rhythms are similarly modified. The present study tested whether an annual cycle in the supply of forage might modify the patterns that are generated by the interaction between photoperiod and endogenous rhythms. Both breeds were subjected to a simulated `Mediterranean' annual cycle in photoperiod (10L : 14D to 14D : 10L) and provided with either constant food supply or a simulated `Mediterranean' annual cycle in food supply. In Merino rams, testicular growth responded to photoperiod, but nutrition dominated those responses. In Suffolk rams, changes in testicular size can be completely out of phase with changes in body mass because they are driven primarily by photoperiod, with only subtle responses to changes in diet. The cycle of testicular growth in the Suffolk was driven by changes in the secretion of gonadotrophins (follicle-stimulating hormone concentrations and luteinizing hormone pulse frequency). By contrast, in the Merino, the nutritionally driven seasonal cycle of testicular growth was associated primarily with changes in body mass and this relationship could not always be explained by changes in gonadotrophin secretion. Melatonin secretion was not affected by food supply. Thus, the `Mediterranean' and `temperate' genotypes have similar endogenous rhythms that are similarly modified by photoperiod but, with respect to seasonal changes in nutrition, they differ in both the nature of their reproductive response and the physiological mechanisms that mediate those responses.

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Blumer, S. E., G. E. Gardner, M. B. Ferguson y A. N. Thompson. "Environmental and genetic factors influence the liveweight of adult Merino and Border Leicester × Merino ewes across multiple sites and years". Animal Production Science 56, n.º 4 (2016): 775. http://dx.doi.org/10.1071/an14419.

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Variation in liveweight change in the ewe flock during periods of poor nutrition can affect farm profitability through the effects of liveweight loss on potential stocking rate, management interventions including supplementary feeding, and ewe and lamb survival and productivity. There is variation between individual animals in their ability to manage periods of poor nutrition, but the links between liveweight change and breeding values in the adult ewe flock have not been quantified. We analysed 5216 liveweight profiles for 2772 ewes managed over 3 years at eight sites across Australia, to define the relative effects of environment, reproductive performance and breeding values on liveweight change. The range in liveweight loss varied from 1.3 kg to 21.6 kg, and for liveweight gain from 0.4 kg to 28.1 kg. Site and year had the largest influence on liveweight change, which demonstrates that seasonal conditions and management were the most important factors influencing liveweight change. Liveweight loss was influenced by previous and current reproductive performance but these effects were small in comparison to the effects of site and year. There were mixed associations with sire breeding values for growth, fat and muscle depending on site. An increase in sire breeding values for fat by 1 mm was associated with a reduction in liveweight loss by up to 1.3 kg regardless of ewe breed, and this was more evident at sites where ewes lost a greater proportion of their liveweight. While management had the greatest effect on liveweight change, there appears to be scope to use breeding values to select sheep that will lose less weight during periods of poor nutrition in some environments.

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Liu, S. M., N. R. Adams, J. B. Briegel, T. L. Smith y G. B. Martin. "Effect of genetic resistance to gastrointestinal nematodes on plasma concentrations of insulin-like growth factor-1 and leptin in Merino sheep". Australian Journal of Experimental Agriculture 47, n.º 8 (2007): 905. http://dx.doi.org/10.1071/ea06253.

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Gastrointestinal nematode infection in sheep changes the nutritional economy of the host, but little is known about the effects of infection on the hormonal systems that regulate the metabolism of the animal. This study examined two key hormones, insulin-like growth factor-1 (IGF-1) and leptin, in genetically resistant and random bred control Merino sheep in the presence or absence of nematode infection. Sixty-four 10-month-old Rylington Merino wethers, half from the parasite-resistant line and half from unselected control line, were initially maintained at two body conditions (body condition scores averaged 1.7 and 2.5) in individual pens in an animal house. The animals were kept parasite-free for 9 weeks, then ‘trickle-infected’ with Trichostrongylus colubriformis and Teladorsagia circumcincta larvae, each at a rate of 10 000 per week, for 13 weeks. Each body condition score group was subdivided into two groups at the beginning of the infection procedure and feed supply was controlled at 1× or 1.5× the maintenance metabolisable energy requirement. Plasma IGF-1 concentrations decreased marginally by day 21 of infection, then markedly by day 49, and then remained low until day 84. Plasma leptin concentrations tended to increase during the infection period. Both body condition and feed intake had significant effects on IGF-1 and leptin concentrations, and the higher concentrations were related to the good body condition or high feed intake. The parasite-resistant sheep had consistently higher concentrations of IGF-1 compared with the controls, whereas the concentrations of leptin were similar. The significant changes in IGF-1 but not leptin suggest that infection may have a more significant impact on protein anabolism, and least impact on lipid metabolism. Selection for parasite resistance appears to result in enhanced protein anabolism.

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Walkom, S. F., F. D. Brien, M. L. Hebart, S. I. Mortimer y W. S. Pitchford. "Season and reproductive status rather than genetics factors influence change in ewe weight and fat over time. 3. Analysis of Merino ewes". Animal Production Science 54, n.º 6 (2014): 821. http://dx.doi.org/10.1071/an13249.

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The profitability of southern Australian sheep production systems depends on the optimisation of stocking rates by meeting the nutritional demands of the breeding ewe while effectively utilising grown pasture. The aim of the study was to evaluate the genetic variation in liveweight and body condition of Merino ewes across their breeding life within a wool-based enterprise. The results were consistent with findings in crossbred ewes and showed that the genetic component of weight and body condition remained constant across the production cycle and age. The overall additive genetic effect accounted for 92% of the genetic variation in weight of Merino ewes bred across five production cycles. A genetic correlation of 0.85 suggested that ewes that were superior at maintaining their condition when rearing a single lamb would maintain this superiority when rearing multiple lambs. To improve weight and condition of Merino ewes during the ‘tough’ times, when nutrient requirements are not met by the pasture, selection can be made at any time and this will result in increased genetic condition at all times.

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Kelly, R. W., J. C. Greeff y I. Macleod. "Lifetime changes in wool production of Merino sheep following differential feeding in fetal and early life". Australian Journal of Agricultural Research 57, n.º 8 (2006): 867. http://dx.doi.org/10.1071/ar05312.

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In commercial Merino farming, a major determinant of profitability is quantity and quality of wool production. We tested the hypothesis that the level of feed restriction commonly encountered by autumn/early winter lambing Merino ewes in southern Australia was sufficient to have a detrimental effect on their progeny’s lifetime wool production. Two periods of feed restriction of the dams were tested, viz. from day 50 to 140 of gestation (Expt 1), and from day 50 of pregnancy to weaning at 12 weeks of age (Expt 2). In order to reduce the numbers of experimental animals required, identical twin lambs were produced by cloning embryos. There was a total of 35 and 22 pairs of clones in Expts 1 and 2 that were recorded to 6.4 and 4.4 years of age, respectively. In Expt 1 it was estimated (i.e. conceptus-free weight) that the submaintenance (Sub-M) ewes lost 18 kg in weight compared with 9 kg by the Control (C) ewes over the period of differential feeding. In Expt 2 the Sub-M ewes lost 10 kg during pregnancy and 10 kg during lactation, compared with a loss of 3 kg and a gain of 4 kg over the same period in the C ewes. Gestation length was 1.3 days shorter (P < 0.01) in the Sub-M than C ewes in Expt 1. Birthweights of the Sub-M lambs were 0.5 kg lighter than the C lambs in Expts 1 (P < 0.01) and 2 (P < 0.05). At 12 weeks of age, liveweights of the lambs in the Sub-M and C treatments were 24.2 and 25.9 kg in Expt 1 (P < 0.01) and 14.0 and 25.0 kg in Expt 2 (P < 0.001). Corresponding liveweights at 4 months of age were 30.9 and 32.5 kg (P < 0.01) and 19.9 and 29.7 kg (P < 0.001), the Sub-M animals producing less clean wool (0.1 and 0.4 kg, P < 0.01 and < 0.001, Expts 1 and 2, respectively), that was finer in Expt 2 (2.7 μm, P < 0.001) than their C counterparts. Throughout the rest of the study the Sub-M animals in Expt 2 (but not Expt 1) were on average 3.2 kg lighter (P ranging from < 0.05 to < 0.001) than C animals. In both experiments the ratio of secondary to primary wool-producing follicles was lower (1.1–2.6 units, P < 0.001) in the Sub-M than C animals. These differences led to (P < 0.05) lower significantly adult clean wool production of 0.17 kg (Expt 1) and 0.24 kg (Expt 2) per annum. There was no significant interaction between nutritional treatment and age of the animal for clean wool production. Within experiments there were no significant differences between nutritional treatments in any of the wool quality measurements. However, when fibre diameter data for both experiments were combined for 3.4 and 4.4 years of age, the Sub-M animals were significantly broader (0.3 μm, P < 0.01) when compared with the C animals. We conclude that Sub-M feeding of the pregnant ewe will permanently affect liveweight, the wool follicle population, and wool production and quality, in Merino sheep. Extension of the period of under feeding into lactation (Expt 2) appears to increase the amplitude of the differences in young animals, which is largely overcome by the time the animal reaches 2.4 years of age.

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O’Neill, H. A., O. B. Einkamerer, B. T. Elago y A. Ganswindt. "Concentrations of faecal glucocorticoid metabolites in South African Mutton Merino sheep fed various sources of roughage". South African Journal of Animal Science 50, n.º 4 (29 de octubre de 2020): 501–6. http://dx.doi.org/10.4314/sajas.v50i4.2.

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The objective of this study was to determine whether various sources of roughage in nutritionally balanced feedlot diets would evoke a stress response in sheep. A nutritional stress response test was performed on 20 ewes, randomly divided into four treatment groups with 5 ewes per group. Ewes were kept individually in metabolic crates for thirty days. Rations were balanced nutritionally, and various sources of roughage were included; T1: alfalfa hay, T2: maize stover, T3: soya hulls; and T4: Eragrostis tef. Faeces was removed manually from the caudal rectum of each ewe at 05h00 and 19h00. Samples were frozen at -20°C until analyses. A total of 520 faecal samples were analysed to determine the concentrations of faecal glucocorticoid metabolites (fGCM) by enzyme immunoassay (EIA). These concentrations were expressed as mass/g dry weight (ng/g DW). Baseline values were determined, and those greater than the mean plus 2 standard deviations were removed. Baseline values were compared between the groups with one-way ANOVA analysis. The average concentrations of fGCM were 178.77 ± 21.7 in the morning and 183.2 ± 14.4 in the evening. Sheep fed T4 had significantly higher fGCM concentrations in both morning (302.0 ± 86.1 ng/g DW) and evening (237.0 ± 48.1 ng/g DW) compared with the other treatment groups. Thus, fGCM concentrations in sheep were related to the source of roughage, and Eragrostis tef caused a stress response. Keywords: animal welfare, cortisol, dietary fibre, selective grazer, stress response

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Blache, Dominique, Pietro Celi, Margaret A. Blackberry, Robyn A. Dynes y Graeme B. Martin. "Decrease in voluntary feed intake and pulsatile luteinizing hormone secretion after intracerebroventricular infusion of recombinant bovine leptin in mature male sheep". Reproduction, Fertility and Development 12, n.º 8 (2000): 373. http://dx.doi.org/10.1071/rd00102.

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The aim of the present study was to determine whether leptin might play a role in the gonadotrophic response of mature merino rams to changes in the level of nutrition in rams fed ad libitum. Recombinant bovine leptin was infused intracerebroventricularly and voluntary food intake (VFI) and luteinizing hormone (LH) pulse frequency were measured. In Experiment 1, rams (n = 5) were infused for 24 h per day for 5 days with vehicle or with leptin (0.04, 0.4 and 4.0g h –1 ). All doses decreased both VFI and LH pulse frequency. In Experiment 2, rams were infused for 24 h per day for 5 days with vehicle (n = 10) or leptin (4 g h –1; n= 5); a sub-group of 5 controls was pair-fed to the leptin-infused group to control for effects of changes in feed intake. LH pulse frequency was reduced equally in both the leptin-infused and pair-fed groups. Leptin did not affect other systems controlled by the hypothalamic–pituitary axis. Thus, rather than stimulate LH secretion, intracerebral leptin specifically inhibits it by reducing food intake, so it is unlikely that effects of nutrition on the reproductive axis in mature rams involves leptin as a single blood-borne signal. A range of nutritional or metabolic inputs may be needed, and perhaps interconnections between neural centres that control appetite and reproduction.

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Hynd, PI. "Effects of nutrition on wool follicle cell kinetics in sheep differing in efficiency of wool production". Australian Journal of Agricultural Research 40, n.º 2 (1989): 409. http://dx.doi.org/10.1071/ar9890409.

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Wide phenotypic variation in fibre output per follicle was generated by selecting sheep (five South Australian strongwool Merinos, one finewool Merino and one Corriedale) on this basis, and by offering these sheep a low-protein diet for 9 weeks, followed by a high-protein diet for a further 8 weeks. Clean wool production was measured over the final 3 weeks of each period, while fibre diameter, the rate of length growth of fibres and a number of follicle characters were measured over the last 7 days of each period. The rate of division of follicle bulb cells and the total volume of the germinative region of the follicle was estimated by image-analysis of bulb sections in skin biopsy samples.With the change from the low-protein diet to the high-protein diet, the rate of clean fleece production was increased by 33% (P<0.002), reflecting an increase in fibre diameter (8%) and rate of length growth of fibres (26%); the volume of the germinative region of the average bulb increased 30% (P<0.012) and the rate of bulb cell division by 35% (P<0.004); cortical cell volume also did not change (923 8m3 v. 965 8m3; the average proportion of fibre cross-sectional area occupied by paracortical cells increased from 0.2 1 to 0.35 ( P < 0.01 0); the proportion of dividing cells entering the fibre cortex ranged from 0.25 to 0.42 (mean, 0.31) between sheep on the low-protein diet, and from 0.22 to 0.39 (mean, 0.32) when the animals were fed the high-protein ration; the effect of diet on cell distribution to fibre and inner root sheath was not significant (P<0.601).Phenotypic differences in fibre output were primarily related to differences in the rate of bulb cell division (r= 0.896, P < 0.001), but inclusion of a term for the proportion of bulb cells entering the fibre cortex, removed an additional, significant proportion of the variance. Cortical cell volume, on the other hand, was poorly related to fibre output.

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19

Poudel, Anit. "SMALL RUMINANTS BREEDING IN MOUNTAIN REGIONS OF NEPAL: CHALLENGES AND OPPORTUNITIES". Big Data In Agriculture 3, n.º 1 (17 de junio de 2021): 35–40. http://dx.doi.org/10.26480/bda.01.2021.35.40.

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Small ruminants (sheep and goat) are essential components of the mixed farming system of Nepal. About 13.6 million small ruminants in the country contributing to the food, nutrition, and economic security has been integral part of the mountain ecosystem and rural economy. Despite of their large population, country is facing great trade deficit in products like meat, milk, wool and fibres. Low production is associated with impoverished productive potential of indigenous breed that are reared under abysmally managed subsistence farming. This study has tried to review the existing breeds, breeding system and opportunities within the challenges to enhance production and productivity of small ruminants. The findings revealed that genetic improvement through selection and crossbreeding with enhance feeding and management practices can be powerful tool in increasing production efficiency of the animal. Crossbred of native breed of sheep Baruwal with exotic breed Polworth and Merino and native breed of goat Khari with exotic breed Boer and Jamunapari gave better performance of many production and reproductive traits. The increased productivity of small ruminants will not only be a boon for small holders but will also greatly contribute to the national economy.

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20

Entwistle, K. W., L. J. Cummins, M. A. Hillard, J. E. Kinder, T. O'Shea, L. R. Piper, J. Thimonier y J. F. Wilkins. "Bernard Michael Bindon — reproductive physiologist, animal scientist, research leader". Australian Journal of Experimental Agriculture 46, n.º 2 (2006): i. http://dx.doi.org/10.1071/ea05222.

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This paper is a foreword to a series of papers commissioned on ‘the impact of science on the beef industry’, where the Beef CRC-related collaborative scientific work of Professor Bernard Michael Bindon will be reviewed. These papers will be presented in March 2006, as part of a ‘festschrift’ to recognise his wider contributions to the Australian livestock industries for over 40 years. Bindon’s career involved basic and applied research in many areas of reproductive physiology, genetics, immunology, nutrition, meat science and more recently genomics, in both sheep and cattle. Together with his collaborators, he made large contributions to animal science by improving the knowledge of mechanisms regulating reproductive functions and in elucidating the physiology and genetics of high fecundity livestock. His collaborative studies with many colleagues of the reproductive biology and genetics of the Booroola Merino were amongst the most extensive ever conducted on domestic livestock. He was instrumental in the development of immunological techniques to control ovulation rate and in examining the application of these and other techniques to increase beef cattle reproductive output. This paper tracks his investigations and achievements both within Australia and internationally. In the later stages of his career he was the major influence in attracting a large investment in Cooperative Research Centres for the Australian cattle industry, in which he directed a multi-disciplinary approach to investigate, develop and disseminate science and technology to improve commercial cattle productivity.

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21

Paganoni, B. L., M. B. Ferguson, S. Fierro, C. Jones, G. A. Kearney, P. R. Kenyon, C. Macleay, C. Vinoles y A. N. Thompson. "Early reproductive losses are a major factor contributing to the poor reproductive performance of Merino ewe lambs mated at 8–10 months of age". Animal Production Science 54, n.º 6 (2014): 762. http://dx.doi.org/10.1071/an13240.

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The reproductive performance of Merino ewe lambs is lower than that achieved by mature ewes and is highly variable. It is likely that embryo loss represents a major source of reproductive wastage in Merino ewe lambs, but to our knowledge no studies have attempted to determine when the major reproductive losses occur or identify predisposing factors that are likely to lead to high rates of pregnancy failures in ewe lambs. After characterising where reproductive losses occurred in Merino ewe lambs mated at 8–10 months of age, we tested the hypothesis that pregnancy failure in ewe lambs is influenced by nutrition and liveweight change around conception and the genetic potential for growth of the ewe lamb. Two-hundred and twenty-four Merino ewe lambs born from 10 sires with Australian Sheep Breeding Values were teased for 14 days using vasectomised rams, and then fed two different diets for 68 days during mating. All ewe lambs were weighed and the appearance of crayon marks on their rump was recorded most days. Blood samples for progesterone assay were collected on Days 5, 12 and 17 after the first record of a crayon mark. Ultrasonography using a trans-rectal probe was used to measure the number of corpora lutea present, as a proxy for ovulation rate, 9 days after the first record of a crayon mark during the mating period. A further trans-rectal ultrasonography was undertaken 30 days after marking from the entire ram to determine pregnancy status and count the number of embryos. Over the entire mating period 54% of ewe lambs were pregnant with 66 fetuses per 100 ewes mated. The average ovulation rate was 150% however up to 84% of this potential was lost by weaning and the major contributor to this apparent deficit was the loss that occurred during the first 17 days after mating. Pregnancy failure was not significantly related to nutrition or liveweight change during mating however, there were significant differences in pregnancy failure between different sire groups. Pregnancy failure was significantly less for ewe lambs from sires with higher breeding values for weight and fat at post-weaning age (8–10 months). Only 60% of ewe lambs had achieved puberty when rams were introduced and only 83% by 35 days after mating. In addition, almost half of the ewe lambs that were mated for the first time during the first 35 days after rams were introduced, but failed to get pregnant, then seemed to skip a cycle or did not cycle again before the end of the 68-day mating period. Liveweight at introduction of entire rams was positively related to fertility, ovulation rate and reproductive rate. This study confirms that selection of sires with higher breeding values for post-weaning weight and fat will increase the fertility and reproductive rate of Merino ewe lambs mated at 8–10 months. This response is due in part to enhancing the onset of puberty and increasing the proportion of ewe lambs cycling at the start of mating and reducing pregnancy failure.

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22

ATES, S., G. KELES, F. INAL, A. GUNES y B. DHEHIBI. "Performance of indigenous and exotic×indigenous sheep breeds fed different diets in spring and the efficiency of feeding system in crop–livestock farming". Journal of Agricultural Science 153, n.º 3 (17 de julio de 2014): 554–69. http://dx.doi.org/10.1017/s0021859614000677.

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SUMMARYGenetic variation in feed efficiency may have a significant impact on sheep production in integrated crop livestock farming systems in dry areas, where the shortage and poor quality of feed is widespread. Thus, the present study was carried out to investigate the effects of sheep genotype and feed source on liveweight gain, feed conversion efficiency and dry matter (DM) intake in feedlot lambs finished on diets based on low-cost forages or a high-cost concentrated feed as a means of assessing the efficiency of this feeding system. Early weaned lambs of the purebred fat-tailed Akkaraman breed were compared with synthetic Anatolian Merino (0·80 German Mutton Merino×0·20 Native Akkaraman) breed. The lambs were kept in individual pens for 8 weeks and fed four diets: daily harvested forages of triticale (T), Hungarian vetch (HV), a triticale-Hungarian vetch mixture (T+HV), and a concentrate-based feed (CF). Lamb liveweight gain (LWG) was monitored during the early (18 April–16 May) and late (17 May–13 June) spring periods. Diet×period and diet×breed interactions were detected in LWG of the lambs. Lambs from both genotypes on the concentrate-based diet had higher liveweight gains, DM intakes and better feed conversion ratios compared with lambs finished on the forage-based diets. The LWG of lambs offered triticale forage decreased from 177 g/head/day in the early spring to 95 g/head/day in the late spring period, as plant maturity increased. Liveweight gains did not change for the other forage rations during the same period. The LWG of Akkaraman lambs were similar for both the early (189 g/head/day) and the late (183 g/head/day) spring periods, whereas Anatolian Merino lambs gained 41 g/head/day less LW and had 3·8 higher feed conversion rate for the late spring period compared with the early spring period. The present study showed that fat-tailed Akkaraman lambs were better able to utilize forages with low nutritive value compared to Anatolian Merino lambs, and may be better suited to semi-arid areas, where crop and livestock are highly integrated in the farming system.

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23

Li, L., S. M. Liu, V. H. Oddy y J. V. Nolan. "Protein synthesis rates in skin components and skeletal muscle of sheep selected for divergent clean fleece weight in response to below- and above-maintenance nutrition". Australian Journal of Agricultural Research 58, n.º 11 (2007): 1031. http://dx.doi.org/10.1071/ar06373.

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Protein metabolism in skin and muscle was studied in Merino wethers selected for high (F+, n = 10) or low (F–, n = 10) estimated breeding values for clean fleece weight, but with similar estimated breeding values for liveweight and fibre diameter, raised to 20 months of age under the same conditions, and then offered two levels of nutrition (0.8 or 1.8 × maintenance) for 37 days. Over 37 days, F+ sheep had greater rate of wool production, liveweight gain, and had greater eye-muscle and fat depth than F– sheep (P < 0.05). Fractional synthesis rates of protein (%/day) in the epidermis, dermis, whole skin and muscle were affected by both feeding level (P < 0.05) and genotype (P < 0.05). The fractional synthesis rates of protein were greater (P < 0.05) in F+ sheep at both levels of intake. There was an interaction (P < 0.01) between genotype and feeding level for the protein fractional synthesis rate in muscle, where F+ sheep were more responsive to higher feed intake. Muscle of F– sheep responded to increased amino acid supply by reducing the rate of protein degradation without altering synthesis rate; whereas muscle of F+ sheep responded by increasing the rates of both protein synthesis and degradation. The overall muscle fractional synthesis rate (1.6%/day) was ~7-times lower than the skin fractional synthesis rate (10.8%/day) in these animals (P < 0.01). F+ sheep had a higher rate of protein synthesis in dermis and whole skin to support their higher wool protein accretion at both levels of feed intake. Muscle protein synthesis rate was greater in F+ sheep offered above-maintenance metabolisable energy (ME) intake than those given below-maintenance ME intake but was unaffected by ME intake in F– sheep. The results indicate that selection for wool growth not only affects production of wool and the wool follicle, but also affects the rate of protein turnover in components of the skin and skeletal muscle.

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24

Pethick, DW y JB Rowe. "The effect of nutrition and exercise in carcass parameters and the level of glycogen in skeletal muscle of Merino sheep". Australian Journal of Agricultural Research 47, n.º 4 (1996): 525. http://dx.doi.org/10.1071/ar9960525.

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This study investigated the effects in sheep of feed intake and exercise training on (i) the level of glycogen in muscle, and (ii) carcass quality traits including growth rate, carcass weight, fat score, and the ultimate pH of muscle. Merino wethers, 12-months-old and starting body weight 38 kg, were individually penned and housed indoors. The effects of nutrition and exercise were tested for 2 levels of activity (sedentary v. exercised) and 4 levels of feed intake (1, 1.3, 1.5, 2.2 x maintenance) with 8 sheep per group housed individually. Exercise training was for 1 h at 8-9 km/h (approx. 55-65 VO2max), 3 times per week from week 4 to 9 of the experiment. The diet was 20% cereal straw, 26% lupin grain, 53% barley grain, mineral and vitamin premix, and virginiamycin. Animals were slaughtered at an abattoir in week 10. Regular exercise reduced growth rate, carcass weight, and fat score, but did not affect intake. At the highest level of intake, carcass weight was reduced by 0.53 kg and fat depth over the 12th rib (GR fat depth) by 6.3 mm, suggesting that muscle yield was increased. At all sampling times, the level of glycogen in the m. semimembranosis (SM) and m. semitendinosis (ST) increased linearly with increasing feed intake. Regular exercise caused increased glycogen level in SM samples immediately post-slaughter and in the SM, ST, and m. longissimus dorsi (LD) 48 h post-slaughter. The ultimate pH of muscle was reduced as the level of feed intake increased for all muscle groups. Exercise caused a reduction in the ultimate pH of the ST with no change for the SM and LD. The results indicate that glycogen levels in muscle are highly responsive to nutrition and regular exercise. In addition, exercise caused a reduction in subcutaneous fat with no change in feed intake.

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Revell, D. K., H. C. Norman, P. E. Vercoe, N. Phillips, A. Toovey, S. Bickell, E. Hulm, S. Hughes y J. Emms. "Australian perennial shrub species add value to the feed base of grazing livestock in low- to medium-rainfall zones". Animal Production Science 53, n.º 11 (2013): 1221. http://dx.doi.org/10.1071/an13238.

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Australian native perennial shrubs that are adapted to drought and infertile soils contribute nutrients to grazing systems that would otherwise support limited ruminant productivity. In this study, we report the nutritive value of 39 Australian shrub species of the genera Atriplex, Rhagodia, Maireana, Chenopodium, Enchylaena, Acacia, Eremophila, and Kennedia. Edible foliage was sampled in winter and summer, and there was little difference in nutritive value between seasons. The in vitro organic matter digestibility of most shrub species was 40–70%. Most species contained medium to high levels of crude protein (12–22% of dry matter, DM) and high concentrations of sulfur (2–8 g/kg DM). In an 8-week grazing experiment in which Merino wethers grazed a ‘shrub system’ containing four shrub species and a sown inter-row of annual pasture, the sheep gained weight during autumn without supplementary feeding. By comparison, sheep fed senesced volunteer pasture and supplementary cereal grain only maintained weight. The forage shrubs provided up to 50% of the total DM intake of sheep grazing the ‘shrub system’ and made a modest contribution to the digestible energy intake of the animals and a large contribution to their crude protein and mineral intake. Considering the timely and predictable provision of limiting nutrients and benefits such as gut health and the provision of shade and shelter, we suggest that Australian shrub species can make a valuable addition to the feed base of low- to medium-rainfall zones in southern Australia.

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26

Brown, D. J., D. B. Savage, G. N. Hinch y S. J. Semple. "Mob-based walk-over weights: similar to the average of individual static weights?" Animal Production Science 52, n.º 7 (2012): 613. http://dx.doi.org/10.1071/an11306.

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Merino ewe liveweight represents an objective measure shown to have a profound effect on production outcomes and therefore research into technology that provides accurate and timely feedback of ewe liveweight change is warranted. Most sheep in Australia are not individually identified and therefore management of sheep is on a flock or ‘mob’ basis. Mob-based walk-over weighing (MBWOW) is a remote weighing concept for sheep flocks whereby animal weights are collected as they pass freely over a strategically placed weighing platform. The weights are then collected by the livestock manager, analysed and interpreted to aid nutritional decision making on a whole-flock basis. The hypothesis tested in this study was that data from MBWOW systems is comparable to data from static weighing sessions. At three sites, MBWOW data was collected simultaneously with monthly static weighing sessions. Raw data from MBWOW from each site was manipulated through a series of methodologies that were compared according to their relationship with the static weight data. All forms of MBWOW data showed a significant relationship with static weighing data (P < 0.05). Using a 25% filter (data within 25% of a predetermined central weight kept) and grouping data into 5-day groups strengthens the relationship between MBWOW data and static weighing data. In 1-day groupings, MBWOW data with a 25% filter and subjectively chosen central weight showed the strongest relationship (R2 = 0.89) with static weighing data. In 5-day groupings, MBWOW data with a 25% filter and reference weight from a previous weighing event as a central weight showed the strongest relationship (R2 = 0.88) to static weighing data. The former MBWOW data manipulation methodology had the least mean numerical difference (±s.d.) between MBWOW data and static weighing data (1.86 ± 0.85 kg), yet the latter had the least mean numerical difference in change-in MBWOW data and change-in static weighing data (1.51 ± 0.39 kg), and as change-in liveweight has the most application to industry, it is recommend as the preferred data manipulation technique. These findings suggest that although MBWOW is not fully congruent with static weighing, a strong relationship (R2 > 0.8) between the two and low mean numerical difference in change-in liveweight indicates that MBWOW has potential to be used to established liveweight profiles for Merino ewes that aid nutritional management.

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Strickland, V. J., G. L. Krebs y W. Potts. "Pumpkin kernel and garlic as alternative treatments for the control of Haemonchus contortus in sheep". Animal Production Science 49, n.º 2 (2009): 139. http://dx.doi.org/10.1071/ea07378.

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Two alternative remedies for controlling Haemonchus contortus in sheep (pumpkin kernel and garlic) were investigated. The experiment involved 18 4-month-old Merino ram lambs with six lambs per treatment group. The lambs were initially drenched to render them worm free, and then infected with 4000 L3 H. contortus larvae, 2 weeks later. Four weeks after infection, faecal egg counts were performed and lambs were allocated into treatment groups and fed their respective diets (control, pumpkin kernel or garlic) for 2 weeks. The lambs were combined into a single group grazing pasture for the last week of the experiment. Faecal worm egg counts (WEC) were carried out weekly for 3 weeks following allocation to treatment diets. Clinical signs of infection observed included liveweight, body condition score and voluntary feed intake. The pumpkin kernel treatment resulted in a 65.5% decrease in the initial level of WEC, but this increased back to the initial level as soon as animals came off treatment. The garlic resulted in a 64.4% decrease in WEC from the initial level and this increased slightly (to 25.5% of the initial level and 43.5% lower than the control) when the animals came off treatment, suggesting that there was a residual effect of the garlic and/or that the garlic had an effect beyond decreasing the fecundity of the parasites. There was no significant difference (P > 0.05) between treatments in liveweight, body condition score or voluntary feed intake. Throughout the experiment voluntary feed intake and liveweight increased while body condition scores remained stable. We concluded that pumpkin kernel and garlic show potential for parasite control by affecting the fecundity of the parasites. Our results also indicate that with good nutrition lambs can cope with high parasite burdens and still be productive during the early stages of infection.

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Gao, Xiang y Hucheng Wang. "Comparative Analysis of Rumen Bacterial Profiles and Functions during Adaption to Different Phenology (Regreen vs. Grassy) in Alpine Merino Sheep with Two Growing Stages on an Alpine Meadow". Fermentation 9, n.º 1 (24 de diciembre de 2022): 16. http://dx.doi.org/10.3390/fermentation9010016.

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Phenological periods can affect the growth of forage, the single food source for grazing animals, and its nutrition and the stage of growth of the animals can affect the rumen microbiota. The aim of this study was to evaluate the effects of phenological periods (regreen vs. grassy) and growing stages (hoggets (1.5 years old) vs. rams (3 years old)) on rumen bacteria communities and functions in Alpine Merion sheep. The result showed that the Alpha diversity indices of ACE (p < 0.001), Chao (p < 0.001), and Shannon (p < 0.001) were higher in the regreen stage. At the phylum level, the abundances of Bacteroidetes (p = 0.003) and Firmicutes (p = 0.017) shifted with plant phenology. The abundance of fiber-degrading bacteria altered at the genus level (p < 0.05). Genes related to fatty acid degradation and metabolism increased in both the growing stage sheep (p < 0.05). In the grassy stage, the abundance of vitamin B6 metabolism (p = 0.046) was increased in hoggets. In summary, this study showed that the phenological stage had a significant effect on the rumen bacterial compartment and functions in two growing stages, while the growing stage only tended to change rumen bacterial diversity.

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Liu, S. M., G. Mata, H. O'Donoghue y D. G. Masters. "The influence of live weight, live-weight change and diet on protein synthesis in the skin and skeletal muscle in young Merino sheep". British Journal of Nutrition 79, n.º 3 (marzo de 1998): 267–74. http://dx.doi.org/10.1079/bjn19980044.

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Wool growth is derived directly from protein synthesis in the skin of sheep, and is affected by the nutritional status of the animals. The present experiment examined both protein synthesis in the skin and muscle and wool growth in Merino lambs differing in live weight, intake and dietary protein source. The experiment was a 23 factorial design: twenty-four 5-month-old lambs initially weighing 33 kg (heavy) or 25 kg (light) were fed on a hay-based diet with either lupin seed or rapeseed meal as the major protein sources to maintain live weight (M) for 56 d, or were fed at 0.6M for 28 d (period 1) followed by 28 d at 1.6M (period 2). Fractional protein synthesis rates (FSR, % per d) in the skin and the m. longissimus dorsi on days 4 and 24 of period 1 and day 4 of period 2 were measured by means of a flooding dose of l-[ring-d5]phenylalanine, and wool growth on a skin patch over period 1 was also measured. The FSR ranged from 13.2 to 20.2% per d in the skin, higher than reported for other breeds, and 1.53–3.07% per d in the muscle. Sheep on the low intake (0.6M) had significant reductions in FSR, protein content (g), protein synthesis (g/d) in the skin, and wool growth (g/d). The heavy lambs had similar FSR to the light lambs, but had a higher skin protein content and total protein synthesis per unit of skin area (100 cm2) and, therefore, grew more wool. The rapeseed-meal diet increased FSR and wool growth only in the light lambs over the short term. The protein deposited in wool over period 1 was 0.185 of the total protein synthesis in the skin, regardless of live weight, intake or diet, a result similar to other breeds. With the changes in dietary intake, protein synthesis in the skin and muscle responded differentially, with nutrient partitioning at sub-maintenance in favour of wool growth but at supra-maintenance, following a nutrient restriction, in favour of weight gain in young growing sheep.

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30

Thompson, A. N. y P. I. Hynd. "Stress-strain properties of individual Merino wool fibres are minor contributors to variations in staple strength induced by genetic selection and nutritional manipulation". Animal Production Science 49, n.º 8 (2009): 668. http://dx.doi.org/10.1071/ea08203.

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This paper investigates the contribution of single fibre stress-strain properties to variations in staple strength induced by both selective breeding for staple strength and nutritional manipulation. Merino weaners (n = 40), selected from ‘sound’ and ‘tender’ lines of staple strength selection flocks, were allocated to feeding regimes designed to induce liveweight changes simulating typical Mediterranean seasonal changes. Average staple strength differed by 5 N/ktex between ‘sound’ and ‘tender’ selection flocks and 18 N/ktex between extreme nutritional treatments. The force-extension properties of individual wool fibres (n = 100 per sheep) were measured using a single fibre strength meter. After normalising for differences in fibre cross-sectional area at the point of break, the key parameters used to describe the stress-strain curve for each fibre were: Young’s modulus (GPa), yield stress (MPa), stress at 15% strain (MPa), stress at break (MPa), strain at break (%) and work to break (MPa). The average stress-strain properties of single fibres differed widely between individual sheep. Stress at break ranged from 163 to 235 MPa (44% range), strain at break ranged from 21 to 44% (103% range) and work to break from 43 to 71 MPa (65% range). There were no significant differences in any of the single fibre properties between the staple strength selection flocks, nor was there any significant interaction (P > 0.05) between staple strength selection flock and nutritional regimes. Nutritional regime had a significant effect on stress at break, strain at break and work to break, but none of the single fibre stress-strain properties removed any appreciable variance in staple strength over and above that accounted for by differences in along- and between-fibre diameter variation. There appears to be little scope for improvement of single fibre stress-strain properties as a means of increasing staple strength in normal production environments. Selection directly for staple strength or indirectly using the fibre diameter variability traits is an effective method to improve staple strength.

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Fraser, M. D. y J. M. Moorby. "Plasma biochemical values in the guanaco (Lama guanicoe) and a comparison with the sheep". Animal Science 66, n.º 1 (febrero de 1998): 209–16. http://dx.doi.org/10.1017/s1357729800008973.

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AbstractAn initial experiment was conducted to investigate the variability of selected metabolites in the plasma from guanacos. A second experiment directly compared plasma biochemical values for guanacos with those for sheep. During the first experiment, jugular blood samples were collected from five mature castrated guanacos using an embedded experimental design. Weekly blood samples were collected at the same time (09.00 h) on the same day each week for 7 weeks. Daily blood samples were collected at the same time each day (09.00 h) during week 5. On day 2 of week 5, blood samples were collected every 3 h from 09.00 h for a 24-h period. No evidence of a cyclical pattern of plasma parameters was observed on a weekly, daily or 3-h basis. During the second experiment, the metabolic profiles of 11 mature castrated guanacos and 11 mature barren ewes (Merino × Welsh Mountain) were compared. Significant differences in plasma concentrations of all metabolites except urea-nitrogen (guanacos -15·42 mmolll, sheep - 15·60 (s.e.d. 1·506) mmolll) were found with values for guanacos v. sheep as follows: glucose (7·63 v. 3·63 (s.e.d. 0·268) mmolll); acetate (0·26 v. 0·48 (s.e.d. 0·035) mmol/l); β hydroxybutyrate (0·06 v. 0·50 (s.e.d. 0·019) mmol/l); albumin (33·4 v. 29·5 (s.e.d. 0·93) g/l); and total protein (53·8 v. 65·6 (s.e.d. 2·12) g/l); (P < 0·001 for all previous variables); non-esterified fatty acids (0·48 v. 0·29 (s.e.d. 0·048) meq per 1; P < 0·01) and a-amino N (2·44 v. 2·66 (s.e.d. 0·088) mmolll; P < 0·05). This study indicates that the reference plasma metabolite concentrations of sheep are not suitable alternatives for use for nutritional or veterinary purposes with guanacos, but those of llamas or alpacas are. The results also suggest that energy capture and transport in camelids may be markedly different from that in conventional ruminants.

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McGregor, B. A., K. L. Butler y M. B. Ferguson. "The allometric relationship between clean mohair growth and the fleece-free liveweight of Angora goats is affected by liveweight change". Animal Production Science 53, n.º 2 (2013): 154. http://dx.doi.org/10.1071/an12070.

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Clean fleece weight (CFWt) is affected by liveweight and change in liveweight in Merino sheep, Angora and cashmere goats. However, how these relationships progress as animals age has not been elucidated. Measurements were made over 12 shearing periods on a population of Angora goats representing the current range and diversity of genetic origins including South African, Texan and interbred admixtures of these and Australian sources. Records of breed, sire, dam, date of birth, dam age, birthweight, birth parity, weaning weight, liveweight, fleece growth and fleece quality were taken for does and castrated males (wethers) (n = 267 animals). Fleece-free liveweights (FFLwt) were determined for each goat at shearing time by subtracting the greasy fleece weight from the liveweight recorded immediately before shearing. The average of the FFLwt at the start of the period and the FFLWt at the end of the period was calculated (AvFFLwt). Liveweight change (LwtCh) was the change in FFLwt over the period between shearings. A restricted maximum likelihood model was developed for CFWt, after log10 transformation, which allowed the observations of the same animal at different ages to be correlated in an unstructured manner. A simple way of describing the results is: CFWt = κ (AvFFLwt)β, where κ is a parameter that can vary in a systematic way with shearing age, shearing treatment and LwtCh; and β is an allometric coefficient that only varies with LwtCh. CFWt was proportional to FFLwt0.67 but only when liveweight was lost at the rate of 5–10 kg during a shearing interval of 6 months. The allometric coefficient declined to 0.3 as LwtCh increased from 10 kg loss to 20 kg gain during a shearing interval. A consequence is that, within an age group of Angora goats, the largest animals will be the least efficient in converting improved nutrition to mohair.

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Strickland, V. J., J. S. Fisher, W. T. Potts y G. W. Hepworth. "Lack of response to garlic fed at different dose rates for the control of Haemonchus contortus in Merino wether lambs". Animal Production Science 49, n.º 12 (2009): 1093. http://dx.doi.org/10.1071/an09057.

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With the increased incidence of parasite resistance to chemical anthelmintics worldwide novel approaches to manage parasite infection, such as medicinal plants and their extracts, are being investigated by the scientific community. The current study tested the effect of three rates of garlic (0.9, 1.8 and 3.6%) in a pelleted ration on Haemonchus contortus in sheep. Thirty-nine Merino wether lambs aged 6 months were divided into five treatment groups, including three garlic dose rates and two control groups that received no garlic. All animals were infected with 4000 L3 H. contortus larvae 3 weeks after allocation to treatments. A positive control group was drenched with abamectin 28 days after infection. The synthetic drench was effective in controlling the parasites, but there was no reduction in either worm egg counts (WEC) or total worm count due to the garlic. The 3.6% garlic treatment had significantly lower (P < 0.05) liveweight, feed intake, body condition score and feed conversion ratio than any of the other treatment groups, suggesting that this level of garlic had a low level of anti-nutritional properties. There was an interaction between faecal WEC and voluntary feed intake over time, with the animals with higher voluntary feed intake having lower WEC over time.

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34

Rowe, J. B., J. V. Nolan, G. de Chaneet, E. Teleni y P. H. Holmes. "The effect of haemonchosis and blood loss into the abomasum on digestion in sheep". British Journal of Nutrition 59, n.º 1 (enero de 1988): 125–39. http://dx.doi.org/10.1079/bjn19880016.

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1. An experiment was conducted to determine the effect of the abomasal parasite, Haemonchus contortus, on the pattern of digestion and nutrient utilization in Merino sheep. There were three groups of sheep: infected with H. contortus (300 larvae/kg live weight) (n 5), sham-infected by transferring blood from the jugular vein to the abomasum, and uninfected (control) sheep (n 9) which were fed daily rations equal to amounts consumed by ‘paired’ animals in the two other treatment groups. A diet containing (g/kg): lucerne (Medicago sativa) chaff 490, oat chaff 480, ground limestone 10, urea 10, and sodium chloride 10, was given in equal amounts at 3-h intervals.2. Continuous intrarumen infusions (8 d) of chromium and ytterbium were made in order to measure the flow of digesta through the rumen, duodenum and ileum with 15NH4Cl included in the infusate for the final 3 d. The loss of blood into the gastrointestinal tract was measured using 51Cr-labelled erythrocytes and the rate of irreversible loss of plasma urea was measured with reference to a single intravenous injection of [14C]urea. Samples of rumen fluid were taken for analysis of volatile fatty acid (VFA) concentrations.3. The infected and sham-infected sheep developed severe anaemia during the period over which digestion and metabolism measurements were made (packed cell volume 0·118 (SE 0·0042) and 0.146 (SE 0·0073) respectively). The corresponding rates of blood loss into the gastrointestinal tracts were 253 (SE 23) and 145 (SE 17) ml/d.4. The proportions of VFA in rumen fluid were altered (P < 0·05) in the infected group with a decrease in the ratio, acetate: propionate (control 3·28, infected 2·58, standard error of difference (SED)(0·21). There was also an increase in rumen fluid outflow rate (P < 0·01) from 4·05 litres/d in the control group to 5.53 litres/d in the infected group (SED) 0·43). Water intake was higher (P < 0·05) in the infected than in the control animals (2·25 and 1·84 litres/d respectively; SED 0·14).5. There was a decrease (P < 0·05) in apparent digestion of organic matter in the forestomachs of infected sheep (0·32 compared with 0·39 in the control, SED 0·02). There was also a decrease (P < 0·05) in the apparent digestion of organic matter across the whole digestive tract (0·65 control, 0·61 infected, SED 0·013).6. There was a loss of 2·6 and 1·8 g blood nitrogen/d into the gastrointestinal tract of the infected and sham-infected sheep respectively. In the infected sheep approximately 50 % of this N was accounted for as additional ammonia leaving the abomasum compared with 20% in the sham-infected group. The additional non-ammonia-N (NAN) entering the duodenum of parasitized or sham-infected animals was reabsorbed before the ileum. There was no effect of infection or sham-infection on the synthesis or digestion of microbial NAN.7. There was a higher (P < 0·001) rate of plasma urea irreversible loss in the infected sheep (8·9 control, 12·2 infected, 10·9 sham-infected, SED (control v. treated) 0·87 g N/d). This was apparently due to increased absorption of ammonia and increased urea excretion and transfer to the gut.8. The results show that in sheep infected with H. contortus there was a considerable increase in the amount of additional endogenous N entering the duodenum. Although the extra N lost into the gastrointestinal tract was reabsorbed before the digesta reached the ileum the animals suffered a net loss of amino acids since part of the reabsorbed N was in the form of ammonia and reabsorbed NAN was apparently ineffectively utilized.

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35

Allen, J. D. y J. M. Gawthornet. "Involvement of the solid phase of rumen digesta in the interaction between copper, molybdenum and sulphur in sheep". British Journal of Nutrition 58, n.º 2 (septiembre de 1987): 265–76. http://dx.doi.org/10.1079/bjn19870094.

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1. Merino sheep fed on a diet of chopped wheaten hay, chopped lucerne (Medicago saliva) hay and oat grain were the source of rumen contents for the study. The diet contained (mg/kg dry weight) 3.3 copper, 0.24 molybdenum and 2.8 sulphur. The effects of adding between 5 and 25 mg Mo/kg as ammonium molybdate (AM) or tetrathiomolybdate (TTM) on the distribution and forms of Cu and Mo in rumen contents were investigated in vivo and in vitro.2. Approximately 88 % of the Cu and 94% of the Mo in rumen contents were associated with the solid phase. When AM or TTM was added to rumen contents in vivo or in vitro the proportion of these elements in the solid phase was increased at the expense of the fluid phase.3. The addition of AM and TTM to rumen contents also decreased the proportion of Cu that was soluble in trichloroacetic acid (50 g/l; TCA) and increased the proportion of Cu that was not extractable by sequential treatment with TCA and neutral detergent.4. Column chromatography of neutral-detergent extracts of rumen contents revealed that TTM treatment caused Cu to be strongly bound to proteins of high molecular weight.5. Addition of sulphide to rumen contents did not result in significant changes in the distribution of Cu between the fluid and solid phases, or in the solubility of Cu in TCA.6. It is postulated that constant removal of TTM from the fluid phase via reaction with proteins and other macromolecules in the solid phase results in greater formation of TTM in vivo than would be expected from solution chemistry. The molybdo-proteins so formed are strong chelators of Cu and may be the agents responsible for the decrease in Cu absorption in animals that consume diets containing high concentrations of Mo.

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36

Gherardi, S. G. y J. L. Black. "Influence of post-rumen supply of nutrients on rumen digesta load and voluntary intake of a roughage by sheep". British Journal of Nutrition 62, n.º 3 (noviembre de 1989): 589–99. http://dx.doi.org/10.1079/bjn19890060.

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The effect of post-rumen supply of nutrients on the rumen digesta load and voluntary consumption of roughage by Border Leicester × Merino ram lambs was investigated. A chopped wheaten hay was offered to the ram lambs (n 24), whose nutrient intake was altered by infusing into the abomasum a liquid supplement, containing reconstituted cow's milk, sodium caseinate, minerals and vitamins, for a period of at least 30 d. Either two or three lambs were allocated by live weight to each of ten rates of nutrient supplementation. The lambs were slaughtered at a target live weight of 31 kg. Voluntary intake of hay was estimated over the last 7 d of feeding. The amounts of digesta and organic matter (OM) in the rumen were measured by emptying after slaughter. The particle size distribution of the digesta was measured by wet sieving and the fractional outflow rate of particulate matter by reference to the marker lignin. Growth rate of the lambs increased linearly as total energy infused increased. The linear increase in growth rate indicated that roughage was not substituted for infused nutrients on a direct energy basis. OM intake from hay declined linearly as the amount of nutrients infused increased. The decline in intake was associated with a decline in both total digesta and the amount of rumen OM. Both the fractional digestion rate of OM and the fractional outflow rate of particulate matter from the rumen were unaffected by the amount of nutrients infused. The results indicated that the rumen digesta load of young sheep fed on a single roughage is directly related to their energy deficit, that is the difference between the capacity of the animals to use energy and the energy available to them for metabolism.

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37

Tjondronegoro, S., GB Martin, SR Sutherland y R. Boukhliq. "Interactions between nutrition, testosterone and inhibin in the control of gonadotrophin secretion in mature rams". Reproduction, Fertility and Development 8, n.º 5 (1996): 855. http://dx.doi.org/10.1071/rd9960855.

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The role of negative feedback by two testicular hormones, testosterone and inhibin, in the gonadotrophin responses of mature male sheep to changes in nutrition was tested. Six days after castration, 24 Merino rams were assigned to groups that were fed either a diet that maintained their initial liveweight (Intermediate diet), or about half of the Intermediate diet (Low diet), or the Intermediate diet with a supplement of lupin grain (High diet). One week after the change of diet, all animals were given subcutaneous testosterone implants, providing plasma testosterone concentrations of 3.06 +/- 0.14 ng mL-1 (mean +/- s.e.m.; n = 24). The implants were left in place for 7 days, during which time all the rams were also injected subcutaneously with 2 mL steroid-free bovine follicular fluid (bFF) every 8 h, to provide inhibin at mean plasma concentrations of 0.40 +/- 0.04 ng mL-1 (n = 24; compared with 1.50 +/- 0.12 ng mL-1 when the animals were intact). Five days after castration, there were significant increases in the frequency of luteinizing hormone (LH) pulses (from 1.83 +/- 0.23 to 17.3 +/- 0.96 pulses per 12 h; mean +/- s.e.m.; n = 24) and concentrations of FSH (from 0.45 +/- 0.07 to 14.19 +/- 2.7 ng mL-1; n = 24). Dietary treatment did not significantly affect these responses. Treatment with bFF and testosterone for 7 days reduced LH-pulse frequencies and follicle-stimulating hormone (FSH) concentrations in all groups. The degree of reduction was least in the group on the High diet, for which the FSH concentration (6.49 +/- 1.96 ng mL-1) and frequency of LH pulses (7.00 +/- 2.31 pulses per 24 h) were significantly higher than those observed in the other groups. The mean frequency of LH pulses did not differ significantly between the Intermediate group (0.88 +/- 0.61 pulses per 24 h) and the Low group (0.25 +/- 0.25 pulses per 24 h). Similarly, FSH concentrations did not differ significantly between these two groups (1.78 +/- 0.46 for the Intermediate group v. 1.33 +/- 0.26 ng mL-1 for the Low group). It is concluded that there is no response to diet in the absence of testicular hormones and the effects of nutrition on LH secretion in castrated rams given exogenous testosterone and inhibin are similar to those observed in intact rams.

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38

Carro, M. D. y M. J. Ranilla. "Influence of different concentrations of disodium fumarate on methane production and fermentation of concentrate feeds by rumen micro-organisms invitro". British Journal of Nutrition 90, n.º 3 (septiembre de 2003): 617–23. http://dx.doi.org/10.1079/bjn2003935.

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Batch cultures of mixed rumen micro-organisms were used to study the effects of different concentrations of disodium fumarate on the fermentation of five concentrate feeds (maize, barley, wheat, sorghum and cassava meal). Rumen contents were collected from four Merino sheep fed lucerne hayad libitumand supplemented with 300 g concentrate/d. Disodium fumarate was added to the incubation bottles to achieve final concentrations of 0, 4, 7 and 10 mm-fumarate. In 17 h incubations, the final pH and total volatile fatty acid production increased (P<0·001) linearly for all substrates as fumarate concentration increased from 0 to 10 mm. Propionate and acetate production increased (P<0·05), while the value of the acetate:propionate ratio decreased (P<0·05) linearly with increasing doses of fumarate. In contrast,l-lactate and NH3-N concentrations in the cultures were not affected (P>0·05) by the addition of fumarate. For all substrates, fumarate treatment decreased (P<0·05) CH4production, the mean values of the decrease being 2·3, 3·8 and 4·8 % for concentrations of 4, 7 and 10 mm-fumarate respectively. Addition of fumarate did not affect (P>0·05) the total gas production. If the results of the present experiment are confirmedin vivo, fumarate could be used as a feed additive for ruminant animals fed high proportions of cereal grains, because it increased pH, acetate and propionate production and it decreased CH4production.

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39

Gonzalez, R. E., D. Labuonora y A. J. E. Russel. "The effects of ewe live weight and body condition score around mating on production from four sheep breeds in extensive grazing systems in Uruguay". Animal Science 64, n.º 1 (febrero de 1997): 139–45. http://dx.doi.org/10.1017/s1357729800015642.

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AbstractEwe live iveights were recorded 4 weeks prior to mating, at the beginning of mating and 22 to 23 days later over a period of 3 years in a flock of some 300 breeding ewes comprising approximately equal numbers of Australian Merino, Ideal (Polwarth), Merilin and Corriedale breeds in a pastorally based grazing system in Uruguay. Multiple-bearing ewes were generally heavier than single-bearing ewes which in turn were heavier than ewes which did not conceive, these differences being greatest in 3- and 4-year-old ewes (i.e. in their second and third breeding seasons). Body condition scores of non-pregnant ewes were lower than those of pregnant ewes, particularly in the 3-and 4-year-old age groups. Ewe live weights achieved prior to, during and at the end of the mating period and the body condition score achieved 4 weeks prior to mating all had significant influences on the number of lambs born (P < 0·01) but there were no significant effects of changes in either live weight or body condition over the 4 weeks prior to mating or during the mating period. The effect of body condition score over the range from 2·0 to 4·0 was to increase the proportions of single- and multiple-bearing ewes and to decrease the proportion of non-pregnant ewes such that the number of lambs born per ewe mated increased from 0·94 to 1·38. Fleece weights differed significantly between breeds, Corriedales having the heaviest fleeces and Merilins the lightest (4·26 and 3·22 kg respectively). Wool production was also significantly and positively affected by age (P < 0·01) and by ewe weight at mating (P < 0·01). The results demonstrate the importance of giving preferential nutritional treatment to younger ewes to ensure a satisfactory subsequent lambing performance and improved wool production.

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40

Ryan, JP, JR Hunton y WM Maxwell. "Increased production of sheep embryos following superovulation of Merino ewes with a combination of pregnant mare serum gonadotrophin and follicle stimulating hormone". Reproduction, Fertility and Development 3, n.º 5 (1991): 551. http://dx.doi.org/10.1071/rd9910551.

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In a factorially designed experiment (N = 321), 0, 800 or 1600 I.U. pregnant mare serum gonadotrophin (PMSG) were administered in combination with 0, 12 or 18 mg follicle stimulating hormone (FSH-P) to superovulate Merino ewes in autumn and spring. A moderate dose of PMSG (800 I.U.) in conjunction with 12 or 18 mg FSH-P increased the ovulation rate above that observed when FSH-P was used alone. This was accomplished by (i) increasing the proportion of ewes that exhibited a superovulatory response (greater than 3 corpora lutea (CL) or persistent large follicles (LF): 69/70 (99%) v. 55/74 (74%), P less than 0.001), and (ii) in those ewes that exhibited a superovulatory response, by an additive effect of exogenous gonadotrophin (14.8 +/- 0.9 CL (69) v. 11.3 +/- 0.9 CL (55), P less than 0.01) without increasing the incidence of LF. The use of 1600 I.U. PMSG in conjunction with 12 or 18 mg FSH-P was characterized by an increase in the number of LF and, in comparison with 800 I.U. PMSG, a reduction in ovulation rate. Season had no effect on the numbers of CL, but total ovarian response (CL + LF) was higher in autumn than in spring (P less than 0.01), because of a greater incidence of LF (P less than 0.001). The proportion of ewes with regressed CL was higher in autumn than in spring (53/143 (37%) v. 32/156 (21%), P less than 0.01), and increased with increased dose of gonadotrophin. Furthermore, a nutritional component to the incidence of ewes with regressed CL was suggested by the observation that the mean concentration of plasma glucose was higher for ewes with normal CL than for ewes with regressed CL (P less than 0.05). Rates of ova or embryo recovery, fertilization and embryo development generally declined with an increase in the incidence of LF as a result of increases in the dose of gonadotrophin and season of administration.

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41

Morrison, M., R. M. Murray y A. N. Boniface. "Nutrient metabolism and rumen micro-organisms in sheep fed a poor-quality tropical grass hay supplemented with sulphate". Journal of Agricultural Science 115, n.º 2 (octubre de 1990): 269–75. http://dx.doi.org/10.1017/s0021859600075237.

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SUMMARYA feeding trial was performed during 1986, in Townsville, Australia, to describe alterations in nutrient metabolism, and the coincident gross changes in rumen microbiology, when a sulphurdeficient diet was supplemented with inorganic sulphur. Eight Merino sheep were fedad libituma spear grass (Heteropogon contortus) hay of low sulphur content (0·4 g/kg DM), supplemented with all other essential minerals. Upon supplementation, daily sulphur intake was increased toc.0·75 g and four animals continued to be fedad libitum(group A) whilst the remaining animals were restricted in feed intake (group B). Sulphur supplementation caused a twofold increase in the feed intake of group A (P< 0·05). In both groups of animals, sulphur supplementation increased the fermentation of cotton thread cellulose (P< 0·05), as well as of ground plant dry matter (P< 0·05), suspended in the rumen in nylon bags for 24 and 48 h. The apparent digestibility of organic matter (AOMD) was also increased by sulphur supplementation; from 30·6 to 39·3% in group A (P< 0·05) and from 35·1 to 41·5% in group B (P> 0·05). The difference in AOMD between groups with sulphur supplementation was not significant, despite group B maintaining a longer retention of fluid digesta in the rumen (20·7 v. 25·3 h) with a significantly lowered rumen volume (4·68 v 3·67 litres,P< 0·05) and outflow of fluid digesta from this site (5·31 v 3·58 litres/day,P< 0·05). Sulphur supplementation increased the molar proportion of acetic acid in rumen fluid (P< 0·05) but lowered propionic and butyric acids in group A (P< 0·05). Only the molar proportion of propionic acid in rumen fluid was significantly lowered in group B (P< 0·05). In both groups of animals, counts of fluid-borne rumen bacteria, protozoa and sporangia of rumen anaerobic fungi (RAF) all increased significantly with sulphur supplementation (P< 0·05 in all instances), but no significant differences were observed between groups in microbial counts, despite the different feeding regimes. The increase in sporangial forms of RAF was most marked; no sporangial forms were detectable until the diet was supplemented with sulphate and measurable concentrations of rumen sulphide were observed. This is the first account of nondetectable concentrations of RAF brought about by the nutritional status of the diet.

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42

Carro, M. D. y M. J. Ranilla. "Effect of the addition of malate onin vitrorumen fermentation of cereal grains". British Journal of Nutrition 89, n.º 2 (febrero de 2003): 181–88. http://dx.doi.org/10.1079/bjn2002759.

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Batch cultures of mixed rumen micro-organisms were used to study the effects of different concentrations of malate (Rumalato®; Norel & Nature S.A., Barcelona, Spain; composed of disodium malate–calcium malate (0·16:0·84, w/w)) on the fermentation of four cereal grains (maize, barley, wheat and sorghum). Rumen contents were collected from four Merino sheep fed lucerne hayad libitumand supplemented with 300 g concentrate/d. Rumalato® was added to the incubation bottles to achieve final concentrations of 0, 4, 7 and 10 mM-MALATE. Gas production was measured at regular intervals up to 120 h. Malate increased (P<0·01) the average fermentation rate of all substrates, and the lag time decreased (P<0·05) linearly with increasing concentrations of malate for all substrates, with the exception of sorghum. in 17 h incubations, the final pH and total volatile fatty acid production increased (P<0·001) linearly for all substrates as malate concentration increased from 0 TO 10 mM. Propionate and butyrate production increased (P<0·05), while the value of the acetate: propionate ratio and L-lactate concentrations decreased (P<0·05) linearly with increasing doses of malate. Malate treatment increased (P<0·05) the CO2production and decreased the production of CH4, although this effect was not significant (P>0·05) for maize. Malate at 4 and 7 mm increased (P<0·05) optical density of the cultures measured at 600 nm for maize, with no differences for the other substrates. The results indicate that malate may be used as a feed additive for ruminant animals fed high proportions of cereal grains, because it increased pH and propionate production and decreased CH4production and L-lactate concentrations; however, in general, no beneficial effects of 10 compared with 7 mM-malate were observed.

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43

Castellaro, Giorgio, Isaí Ochoa, Consuelo Borie y Víctor H. Parraguez. "Effects of Strategic Supplementation with Lupinus angustifolius and Avena sativa Grains on Colostrum Quality and Passive Immunological Transfer to Newborn Lambs". Animals 12, n.º 22 (16 de noviembre de 2022): 3159. http://dx.doi.org/10.3390/ani12223159.

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The aim of the present study was to evaluate the effect of two types of nutritional supplementation during late gestation on the chemical composition, energy value, and IgG concentration in the colostrum and the IgG concentration in the blood serum of lambs. Pregnant Merino Precoz ewes (n = 36) carrying single fetuses were used. Animals were kept grazing on the Mediterranean annual grassland. From day ~90 of pregnancy, animals were allocated into three groups: daily supplementation with oat grain or lupine grain and a control group without supplementation. Immediately after parturition, colostrum was collected from each ewe, and a blood sample was taken from the lambs 24 h after birth. For the evaluation of the chemical composition of the colostrum, an EKOMILK® milk analyzer was used. The energy value of the colostrum was calorimetrically evaluated. IgG concentrations were measured by simple radial immunodiffusion. Data were analyzed by analysis of variance. Colostrum content of protein and non-fat solids was higher in the group supplemented with oat grain than in the lupine grain supplemented and control groups (p ≤ 0.05). In contrast, ewes supplemented with lupine grain had the highest concentration of fat in their colostrum (p ≤ 0.05). Oat grain supplementation resulted in higher concentrations of IgG, both in sheep colostrum and in the blood serum of their lambs (p ≤ 0.05), being higher than those observed in the lupine grain and control groups. Ewes that gave birth to male lambs had significantly higher concentrations of IgG in their colostrum compared to ewes that gave birth to females (p ≤ 0.05). The colostral IgG concentration positively correlated with the serum IgG concentration of the lambs (r = 0.32; p ≤ 0.05). The results indicate that the quality of colostrum and the immunological status of the newborn lambs can be improved by supplementation with oat grain.

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44

Allingham, P. G., W. Barris, A. Reverter, V. Hilsenstein, R. van de Ven y D. L. Hopkins. "Sire and growth-path effects on sheep meat production. 3. Fascicular structure of lamb loin muscle (m. longissimus lumborum) and the impact on eating quality". Animal Production Science 49, n.º 3 (2009): 239. http://dx.doi.org/10.1071/ea08163.

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The effects of sire genetics and growth path on the fascicular structure (FS) of lamb loin muscle (m. longissimus lumborum; LL) and the consequences for eating quality were studied in progeny (n = 299) of 20 Poll Dorset sires and Merino ewes. Sires were selected on the basis of their Australian sheep breeding values (ASBV) for post-weaning growth (PWWT), loin eye muscle depth (PEMD) and subcutaneous fat (PFAT). Growth of lambs was varied by time of weaning (early or late) and by feeding level within weaning group, where lambs were either fully fed throughout or were feed restricted for 55 days then re-alimented to achieve liveweight of ~45 kg at slaughter. The FS variables were determined in differentially stained histological sections of LL by using automated image segmentation and circle geometry methodology and were defined as percentage connective tissue, perimysial seam thickness and fascicular width. Sire ASBV was not a significant covariate to measures of FS, despite ASBV-related effects on growth, carcass leanness and fatness. Independent of weaning time, faster growth was induced by re-alimentation of feed-restricted lambs, resulting in LL with less connective tissue as a percentage of cross-sectional area and larger fascicles than for fully fed peers. The direction of the perimysial seam thickness response varied with treatment and time of weaning. Rapid growth of re-alimented early weaned restricted lambs resulted in thinner seams than for fully fed peers, whereas the opposite response was observed in the late-weaned lamb contrast. This suggests that the weight and age of the lamb at the time of nutritional compromise and re-alimentation are important factors in determining the thickness of perimysial connective-tissue seams. Whilst the evidence confirms differential accretion of the myofibrillar and connective tissues and despite reports of positive effects on tenderness brought about by such changes, variation in structural measures was not associated with variation in either objective measures (compression) or sensory scores for tenderness of the loin muscle. The data from the present study support the tenet that rapid growth before slaughter, combined with appropriate sire genetics, will not compromise the physical characteristics and sensory qualities of the meat.

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45

Raeside, M. C., M. Robertson, Z. N. Nie, D. L. Partington, J. L. Jacobs y R. Behrendt. "Dietary choice and grazing behaviour of sheep on spatially arranged pasture systems. 2. Wether lamb growth and carcass weight at slaughter". Animal Production Science 57, n.º 4 (2017): 710. http://dx.doi.org/10.1071/an15540.

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Dry matter production and nutritive characteristics of the pasture feedbase during autumn are key drivers of profitability in Australia’s prime lamb systems. An experiment was conducted to test the hypothesis that offering lambs dietary choice through spatially separated combinations of perennial ryegrass (Lolium perenne L.), plantain (Plantago lanceolata L.) and/or lucerne (Medicago sativa L.) improves the post-weaning liveweight gain, condition score (CS), pre- and post-slaughter carcass characteristics and reduces the internal parasite burdens of wether lambs finished to a slaughter weight over autumn, relative to lambs offered no dietary choice. The experiment tested seven treatments, replicated four times in a randomised complete block design with plot sizes of 1 ± 0.1 ha. The treatments were: 100% perennial ryegrass (PR), 100% plantain (PL), 100% lucerne (LU), 50 : 50 perennial ryegrass/plantain (PR + PL), 50 : 50 perennial ryegrass/lucerne (PR + LU), 50 : 50 plantain/lucerne (PL + LU) and 33 : 33 : 33 perennial ryegrass/plantain/lucerne (PR + PL + LU). Plots were grazed by weaned lambs between March and June 2011. The lambs had been born between 3 August and 7 September 2010 and were derived from either Coopworth composite dams joined to Coopworth maternal sires or from Merino dams (Toland or Centreplus bloodlines) joined to Border Leicester sires. Backgrounding the lambs on a pasture system that contained lucerne during the lactation to weaning period increased (P < 0.05) liveweight at slaughter by 8% and hot carcass weight by 10%, relative to lambs backgrounded on perennial ryegrass. Finishing lambs on the LU treatment between weaning and slaughter increased (P < 0.05) liveweight at slaughter by 11%, CS at slaughter by 0.3 units, hot carcass weight by 16%, carcass CFAT (measured over the loin) by 2.5 mm, carcass eye muscle depth by 1.1 mm and carcass GRFAT (total tissue depth at 11/12th rib, 11 cm from mid line) by 3.8 mm, relative to lambs finished on the PR treatment. Finishing lambs on LU + PR, LU + PL or LU + PR + PL did not (P > 0.05) improve any of the measured parameters, relative to finishing lambs on the LU treatment. The PL and PR treatments did not differ (P > 0.05) in liveweight at slaughter, CS at slaughter or carcass characteristics, but the PL treatment had lower (P < 0.05) liveweight gain than the PR treatment during the first 2 weeks of the experiment (39 g/day vs 330 g/day), which was later partially compensated for. Our hypothesis has not been supported given that the use of spatially arranged mixes resulted in no improvement in liveweight gain, CS, carcass characteristics or internal parasite burdens relative to the comparable single species sward.

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Khazaal, K., M. T. Dentinho, J. M. Ribeiro y E. R. Ørskov. "A comparison of gas production during incubation with rumen contents in vitro and nylon bag degradability as predictors of the apparent digestibility in vivo and the voluntary intake of hays". Animal Science 57, n.º 1 (agosto de 1993): 105–12. http://dx.doi.org/10.1017/s0003356100006668.

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AbstractTen hays harvested at three stages (early bloom MB, mid bloom MB or in seed) made from lucerne (Medicago sativaj, sweet clover (Melilotus segetalis), Persian clover (Trifolium resupinatum) and pre-bloom (PB) Italian ryegrass (Lolium multiflorum var.), were offered ad libitum to four Merino male sheep and daily intake (g dry matter (DM) per kg M0·75) and DM apparent digestibility (DMD) were measured. In sacco DM degradation (g per 100 g DM), gas production (ml per 200 mg DM), in vitro digestibility and fibre composition (g/kg DM) of the hays were also studied. Gas production or DM degradation were calculated at 6, 12, 24, 48, 72 or 96 h and their kinetics were described using the equation p = a + b(1 - e-ct). Intake and in vivo DMD of the hays were variable (P < 0·01). Lucerne EB and Persian clover (all stages) had the highest nutritive value, whereas sweet clover (all stages) had the lowest. Apart from neutral-detergent fibre, which was only related to intake (r = -0·68; P < 0·05), chemical components and in vitro digestibility were poorly (P > 0·05) related to animal performance. Between 12 and 96 h incubation, intake and in vivo DMD were better related to DM degradation (r = 0·79 to 0·83; r = 0·61 to 0·77) than to gas production (r = 0·73 to 0·80; r = 0·58 to 0·78). Prediction of intake and in vivo DMD from the (a + b) values did not provide a great advantage over using some of the static values of gas production or DM degradation.Multiple regression using separated kinetics of degradation resulted in highest accuracy for predicting intake and apparent digestibility from gas production (R2 = 0·63; R2 = 0·78) and nylon bag degradability (R2 = 0·77; R2 = 0·89). It was concluded that the gas test has good potentiality as it was capable of predicting not only apparent digestibility, but also intake to a level close to that of the nylon bag technique.

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Marino, Rosaria, Mariangela Caroprese, Giovanni Annicchiarico, Francesco Ciampi, Maria Ciliberti, Antonella della Malva, Antonella Santillo, Agostino Sevi y Marzia Albenzio. "Effect of Diet Supplementation with Quinoa Seed and/or Linseed on Immune Response, Productivity and Meat Quality in Merinos Derived Lambs". Animals 8, n.º 11 (10 de noviembre de 2018): 204. http://dx.doi.org/10.3390/ani8110204.

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In the last years several studies have investigated the strong relation between nutrition and immune response in the livestock production, particularly in dairy cattle and sheep. The aim of this study was to evaluate the effects of supplementation based on linseed, quinoa seeds and their combination on welfare, productivity and quality of meat from merinos derived lambs. 32 weaned lambs were divided into 4 experimental groups: quinoa (Q), linseed (LS) and combination of quinoa and linseed (LS + Q) that received the respective supplementation and control group (C) without supplementation. Lambs from all supplemented groups showed lower plasma urea, creatinine and cholesterol than control. Both linseed and quinoa supplementation enhanced the cell-mediated immune responses of lambs, furthermore, linseed supplementation resulted in the lowest level of cortisol secretion after handling, loading and transport. Meat from lambs supplemented with linseed and LS + Q showed the highest pH, at 1 and 3 h post-mortem, while, meat from all supplemented groups was more tender than meat from control. Results indicated that linseed and quinoa seeds supplementation can help the animal to cope with stressful events due to the close link between stress responses and the immune system and for improving meat quality in terms of better tenderness.

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48

Ranilla, M. J., S. López, F. J. Giráldez, C. Valdés y M. D. Carro. "Comparative digestibility and digesta flow kinetics in two breeds of sheep". Animal Science 66, n.º 2 (abril de 1998): 389–96. http://dx.doi.org/10.1017/s1357729800009528.

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AbstractA study was conducted to compare apparent digestibility and digesta flow kinetics in the whole digestive tract in two breeds of sheep (Churra and Merino) offered alfalfa hay at about maintenance. Ten mature sheep (five Churra and five Merino) each fitted with a rumen cannula were used in the study. Apparent digestibility was determined by total faecal collection. Liquid (Co-EDTA) and solid (Cr-mordanted fibre) markers were used to estimate rumen volumes and digesta flows. There were no significant differences between Churra and Merino sheep either in dry-matter or fibre apparent digestibility (P > 0·05). Liquid and solid passage rates did not differ between breeds and the estimated total mean retention times were similar for both genotypes. The volume of liquid in the rumen was proportionately 0·14 greater in Churra than in Merino sheep, although the difference was not significant. Estimated saliva secretion was greater in Churra (11·6 (s.e. 0·77) I/day) than in Merino sheep (10·5 (s.e. 0·72) I/day) but the difference did not reach statistical significance. Solid contents of the rumen did not differ between breeds. Rumen particle density was lowest at 2 h after feeding and remained stable at other sampling times, with no significant differences between breeds. There were no significant differences between breeds in the urinary excretion of total purine derivatives but urinary excretion of allantoin and microbial nitrogen supply tended to be higher in Merino than in Churra sheep (P < 0·20). This was attributed to the smaller rumen pool size of Merino (8·0 (s.e. 0·62) kg) compared with Churra sheep (9·2 (s.e. 0·63) kg). The study indicated that there were no apparent breed differences between Churra and Merino sheep in digestibility and digesta passage when they were given a good-quality forage at a low level of intake.

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Greeff, J. C., L. Bouwer y J. H. Hofmeyr. "Biological efficiency of meat and wool production of seven sheep genotypes". Animal Science 61, n.º 2 (octubre de 1995): 259–64. http://dx.doi.org/10.1017/s1357729800013783.

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AbstractOne hundred and thirty-two ewes of the Merino (M), Finn × Merino (FLXM), Border Leicester × Merino (BLXM), Bleu de Maine × Merino (BMXM), Texel × Merino (TXM), Cheviot × Merino (ChXM) and Merino Landsheep × Merino (MLXM) were evaluated for efficiency of lamb production. Individual food intakes of every ewe and also of her lamb(s) were determined over a complete production cycle. Efficiency of lamb production (kg lamb marketed at 35 kg live mass per kg food consumed by the ewe and her lamb(s)) indicated that the FLXM was the most efficient, followed by the TXM, Merino, MLXM, BLXM, ChXM and the BMXM was the least efficient. No significant differences (P < 0·05) were found between genotypes for efficiency of lamb production for ewes producing and rearing singletons until 35 kg live mass with ewe mass included as a covariate. Efficiency of wool production of the Merino was significantly (T < 0·001) higher than that of the other crosses. These results emphasize the importance of reproduction traits in improving efficiency of lamb production.

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50

Ranilla, M. J., M. D. Carro, C. Valdés, F. J. Giráldez y S. López. "A comparative study of ruminal activity in Churra and Merino sheep offered alfalfa hay". Animal Science 65, n.º 1 (agosto de 1997): 121–28. http://dx.doi.org/10.1017/s1357729800016374.

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AbstractA study was carried out to compare the fermentation parameters and kinetics of digestion of a range of different foods in the rumen of two breeds of sheep (Churra and Merino). Ten mature sheep (five Churra and five Merino), each fitted with a rumen cannula, were used in this study. In situ rumen degradability of both dry matter (DM) and cell wall was greater in Churra than in Merino sheep, the breed differences being significant for most of the foods used in the study (P < 0·05). These differences were greater when the foods had a higher cell wall concentration and this could be related to differences in the ruminal environment. However, when the foods were incubated with rumen fluid their in vitro organic matter (OM) degradability was similar in both breeds. Rumen pH was higher (P < 0·05) and ammonia concentrations were lower (P < 0·05) in Churra than in Merino sheep. Rumen volatile fatty acid concentrations tended to be higher in Merino than in Churra sheep, though differences were only significant just before feeding (P < 0·05). The ratio acetate: propionate was higher in the Churra than Merino breed before and 12 h after feeding (P < 0·05). Protozoa numbers in rumen liquid were similar for both genotypes. The greater degradation of forages in the rumen of Churra sheep is discussed in relation to the possible higher activity of fibre-degrading micro-organisms and the greater buffering capacity of the rumen contents against fermentation acids, which could result in more favourable conditions for the microbial degradation of foods in the rumen.

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