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1
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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Doyle, PT, RA Love y TW Plaisted. "Mineral supplementation and wool production of young Merino sheep on the south coast of Western Australia". Australian Journal of Experimental Agriculture 35, n.º 4 (1995): 437. http://dx.doi.org/10.1071/ea9950437.
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Wool-free liveweight change (LWC), wool growth rate, annual wool production, and wool characteristics of young Merino wethers fed supplements of lupins with gypsum or a multi-element mineral lick were examined in 12 experiments at 5 farms between 1989 and 1992. The source of sheep varied between experiments; age was 4.5-6.5 months and liveweight 28-37 kg at the beginning of supplementation. Sheep were fed lupins, lupins coated with gypsum (15-20 g/kg lupins), or lupins along with access to the mineral lick (offered at 140 g/sheep.week). The amount of lupins offered in all treatments within any experiment was the same. Supplementary feeding varied between experiments from 150 to 240 days. The sheep grazed annual pastures at stocking rates of 8-1 6.7ha. Average lick intake was 12-18 g/sheep. day. During supplementary feeding, there was considerable variation in LWC (-80 to +110 g/day) and clean wool growth rates (3.8-15.1 g/day) within and between experiments. However, there was no significant positive effect of gypsum or mineral lick supplementation on LWC or clean wool growth rates during or after supplementary feeding in any experiment. There were positive (P<0.01) relationships between LWC and clean wool growth rates during supplementation. Also, for some spring-shorn sheep types, staple strength of wool was linearly related (P<0.01) to LWC in the period before the position of break in the wool staple. Annual wool production, average fibre diameter, and staple strength of midside wool were not significantly increased by supplements of gypsum or mineral lick in any experiment.
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Murray, PJ, JB Rowe, EM Aitchison y SG Winslow. "Liveweight gain and wool growth in sheep fed rations containing virginiamycin". Australian Journal of Experimental Agriculture 32, n.º 8 (1992): 1037. http://dx.doi.org/10.1071/ea9921037.
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The feed additive virginiamycin was evaluated for its potential to improve wool growth and liveweight gain in Merino sheep in 2 experiments. In the first experiment 84 wethers (about 10 months old) were housed individually and fed ad libitum a pelleted diet based on lucerne chaff, lupin, and barley grain. Control sheep (28) were fed an unmedicated diet, and 14 in each of 4 groups were given diets containing 10, 20, 40, or 60 mg virginiamycin/kg pellets. Virginiamycin was found to reduce feed intake during the first 4-5 weeks of the experiment when included at levels 220 g/t. There was a dose-related reduction in liveweight gain. There was no significant effect of virginiamycin on wool growth. In the second experiment, weaners and adults from 2 locations in Western Australia, Mount Barker (relatively high rainfall) and Wongan Hills (relatively low rainfall and shorter pasture-growing period), were housed individually in a shed and fed a pelleted diet at rates equivalent to 3.5 and 3.1%, respectively, of liveweight for weaners and adults. The pelleted ration was based on wheat and lucerne chaff, lupin grain, and fishmeal. Virginiamycin was included at 20 mg/kg pellets for 16 of 40 sheep of each age and location. The remaining sheep were fed the unmedicated diet. Feed conversion and liveweight gain improved (P<0.05) in response to the inclusion of virginiamycin during the first 4 weeks of the trial, but wool growth was reduced over the same period. Virginiamycin had no effect on fibre diameter in sheep in either experiment.
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Thompson, A. N., M. B. Ferguson, A. J. D. Campbell, D. J. Gordon, G. A. Kearney, C. M. Oldham y B. L. Paganoni. "Improving the nutrition of Merino ewes during pregnancy and lactation increases weaning weight and survival of progeny but does not affect their mature size". Animal Production Science 51, n.º 9 (2011): 784. http://dx.doi.org/10.1071/an09139.
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Lamb growth to weaning, and during the period immediately following weaning, influences post-weaning mortality and may affect mature size. The hypothesis tested in the experiments reported in this paper was that changes in the maternal liveweight of Merino ewes during pregnancy and lactation could predict the weight at weaning, post-weaning survival and mature size of their progeny. At two sites (Vic. and WA) in each of two 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. Across the four experiments this resulted in progeny weights ranging from 13.8 to 28.3 kg just before weaning. Lamb growth was primarily related to the amount of feed on offer during lactation, but was also related to the liveweight change of the ewe during pregnancy. These relationships were consistent in both experiments at each site. Weaning weight was strongly associated with post-weaning survival at the Vic. site. Survival rates decreased significantly when weaning weights were below 20 kg. These results indicate that management of ewe and lamb nutrition to maximise growth of lambs before weaning and growing weaners at 30 g/day or more after weaning are important for optimal post-weaning survival. The findings also suggest that the mature size of offspring is unlikely to be adversely affected by pre-weaning nutrition 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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Kirkegaard, J. A., S. J. Sprague, H. Dove, W. M. Kelman, S. J. Marcroft, A. Lieschke, G. N. Howe y J. M. Graham. "Dual-purpose canola—a new opportunity in mixed farming systems". Australian Journal of Agricultural Research 59, n.º 4 (2008): 291. http://dx.doi.org/10.1071/ar07285.
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The term dual-purpose canola describes the use of a canola crop for forage before seed production. It could potentially provide a profitable and flexible break-crop option for mixed farms, but there have been no studies to test the concept in Australia. We investigated the feasibility of using canola in this way in field experiments near Canberra, Australia, from 2004 to 2006, using European winter and mid–late maturing Australian spring canola varieties. Winter varieties sown from early March to mid-April produced 2.5–5.0 t/ha of biomass providing 0.3–3.5 t/ha of high-quality forage grazed by sheep in winter. The spring varieties produced similar amounts of vegetative biomass from April sowing but were unsuited to the earlier March sowing as they flowered in early winter and did not recover from grazing. The canola forage was readily eaten by sheep; alkane-based estimates of diet composition indicated that >85% of the organic matter intake consisted of canola. Canola forage was also highly digestible (86–88%) and Merino hoggets grew at 210 g/day from a dry matter intake of 1530 g DM/day. The canola generally recovered well when grazed in winter before bud elongation. Delays in flowering associated with heavy grazing ranged from 0 to 4 days when grazed before buds were visible, to 28 days if the crop had commenced flowering. Significant delays in flowering (>14 days) associated with winter grazing did not reduce seed yield or oil content when favourable spring conditions allowed compensatory growth. Yield loss was observed when winter and spring conditions were unfavourable for compensatory growth, or if grazing continued too late into spring (late September) irrespective of seasonal conditions. The yield loss was more than offset by the value of the grazed forage and the mean gross margin for dual-purpose canola over the four experiments was $240 to $500 higher than for grain-only canola depending on the value assumed for the forage. The study indicates there is considerable scope to capture value from grazing early-sown canola crops during winter without significant, uneconomic trade-offs with seed yield. Further investigations in other medium to high rainfall environments in southern Australia are warranted.
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Young, J., P. T. Doyle y P. Booth. "Strip grazing to control wool growth rate of sheep grazing green annual pastures". Australian Journal of Experimental Agriculture 39, n.º 3 (1999): 247. http://dx.doi.org/10.1071/ea98143.
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We compared strip grazing (SG) as a means of controlling wool growth rate, reducing variation in fibre diameter along the staple, and of carrying more Merino sheep through winter on green annual pastures, with set stocking (SS) in 3 experiments. In experiments 1 and 2, SG involved grazing to a residual feed on offer (FOO) of 400 kg DM/ha with an estimated intake of about 0.8 kg DM/day for each sheep. Treatments commenced after pasture establishment in autumn–winter, with both treatments stocked at 20 wethers/ha until late spring. During spring, average liveweight changes were lower (P<0.01) under SG than SS (55 v. 153 g/day experiment 1; –16 v. 217 g/day experiment 2). Strip grazing, compared with SS, reduced (P<0.01) the variation in wool growth rate and fibre diameter along the staple leading to lower (P<0.01) clean wool weights (3.54 v. 3.94 and 2.97 v. 4.12 kg), but finer (P<0.01) (20.9 v. 22.0 and 19.5 v. 21.5 mm), stronger (P<0.01) (28.6 v. 25.3 and 39.9 v. 35.5 N/ktex) wool. However, there was also an increase in vegetable matter content of the wool. The effects on annual pastures were to increase grass (79 v. 48 and 59 v. 25%) and reduce legume (12 v. 36 and 22 v. 54%) content at the end of spring. In experiment 3, two strip grazing treatments were used: SGl with a residual FOO of about 400 kg DM/ha and a stocking rate of 28 wethers/ha; and SGh with a residual FOO of about 800 kg DM/ha and stocking rate of 14 wethers/ha. The stocking rate for SS was 12 wethers/ha. SGl, following an autumn deferment, enabled a stocking rate of 28 wethers/ha to be sustained through winter without supplementary feeding. This is substantially higher than the district average stocking rate of about 7 sheep/ha. Strip grazing reduced (P<0.01) liveweights at the completion of treatments (SGl 41.9 v. SGh 47.9 v. SS 60.3 kg), reduced (P<0.01) clean wool weights (3.40 v. 3.72 v. 4.54 kg) and mean fibre diameter (19.1 v. 19.0 v. 20.9 m), but increased staple strength (21.3 v. 19.0 v. 16.9 N/ktex). These results are discussed in relation to opportunities to utilise strip grazing in sheep production systems on annual pastures in south-western Australia.
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Z, Hernández-Russo. "Effect of Gastrointestinal Nematodes on Reproduction and Lamb Growth in Australian Merino Sheep". Open Access Journal of Veterinary Science & Research 5, n.º 2 (2020): 1–5. http://dx.doi.org/10.23880/oajvsr-16000204.
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Environmental conditions in Uruguay favour the development of gastrointestinal nematodes (GIN) throughout the year, with clinical or subclinical manifestations that cause significant economic losses. The aim of this study was to evaluate the effect of the GIN on fertility, fecundity, reproductive rate and lamb growth in Australian Merino sheep grazing on basalt fields. The study was carried out in a farm located in north of Uruguay. Sixty-eight Merino ewes facing a natural parasite challenge were divided into two groups. Control group was doused with active anthelmintic that have proven efficacy to minimize the effects of parasitic and the parasitized group that did not receive anthelmintic, except rescue dosages. Stool sample of each sheep was collected monthly for egg counts (EPG) of GIN using McMaster technique and nematode genders were identified from infective larvae obtained in cultures by Roberts O’ Sullivan technique. Artificial insemination and ewes were mated for new service, and pregnancy condition was diagnosed by ultrasound. Lambing control was made and lambs were weighed at birth and marking. The evolution of EPG values showed significant differences between groups at the end of gestation and lactation. Haemonchus spp. was the main gender of nematodes found, followed by Trichostrongylus spp. Fertility was 95 % versus 90 %; fecundity 87 % versus 63 % and reproductive rate 73 % versus 47 % for the control group and the parasitized one respectively. No significant differences were recorded in birth-weight. However market-weight and lamb daily gain were lower in the parasitized group. The effect of natural infection GIN was evident in lower reproductive performance of Australian Merino sheep.
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Bowen, M. K., P. M. Pepper, J. L. Winkleman, R. C. McPhie y M. R. Winter. "Using automated supplementation systems to meet growth targets for grazing sheep". Australian Journal of Experimental Agriculture 48, n.º 9 (2008): 1201. http://dx.doi.org/10.1071/ea07412.
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Remote drafting technology now available for sheep allows targeted supplementation of individuals within a grazing flock. This paper reports results of three experiments. Experiment 1 examined the weight change of Merino wethers allowed access to either lupin grain or whole cottonseed 0, 1, 2 or 7 days/week for 6 weeks. Experiment 2 examined the weight change of Merino wethers allowed access to either lupins or a sorghum + cottonseed meal (CSM) supplement 0, 2, 4 or 7 days/week for 8 weeks. Experiment 3 investigated the relationship between five allocations of trough space at the supplement self-feeders (5–50 cm/sheep) and the weight change of Merino wethers allowed access to lupins 1 day/week for 8 weeks. In all experiments, the Merino wethers had free access as a single group to drinking water and low quality hay in a large group pen and were allowed access to supplement once per day on their scheduled days of access. No water was available in the areas containing supplement, but one-way flow gates allowed animals to return to the group pen in their own time. There was a linear response in growth rate to increased frequency of access to lupins in Experiments 1 and 2, with each additional day of access increasing liveweight gain by 26 and 21 g/day, respectively. Similarly, the response to the sorghum + CSM supplement was linear, although significantly lower (P < 0.05), at 12 g/day. Providing access to whole cottonseed resulted in no significant change in growth rate compared with the control animals. In Experiment 3, decreasing trough space from 50 to 5 cm/sheep had no effect on sheep liveweight change. It was concluded that the relationships developed here, for growth response to increased frequency of access to lupins or a sorghum + CSM supplement, could be used to indicate the most appropriate frequency of access to supplement, through a remote drafting unit, to achieve sheep weight change targets. Also, that a trough space of 5 cm/sheep appears adequate in this supplementation system.
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Salvatore, L., D. Allen, K. L. Butler, D. Tucman, A. Elkins, D. W. Pethick y F. R. Dunshea. "Factors affecting the concentration of short branched-chain fatty acids in sheep fat". Australian Journal of Experimental Agriculture 47, n.º 10 (2007): 1201. http://dx.doi.org/10.1071/ea07037.
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The concentration of short branched-chain fatty acids, specifically 4-methyloctanoic acid (MOA) and 4-methylnonanoic acid (MNA), in subcutaneous fat were determined in five genotypes (Poll Dorset × Border Leicester Merino, Poll Dorset × Merino, Poll Dorsetmuscling × Merino, Merino × Merino, Border Leicester × Merino) of Australian sheep. In total, 264 ewes and wethers, either 8 or 22 months of age, were selected for genotype, age and gender. These animals were sired by 16 rams that were selected for growth based on estimated breeding values (EBVs), except for one group (Poll Dorsetmuscling × Merino), which was selected for muscling based on EBVs. There was a strong relationship between the concentration of MOA and MNA at 8 and 22 months of age. There were no differences between lambs sired by Poll Dorset rams selected for muscling or growth. The 8- and 22-month-old Poll Dorset × Merino sheep had higher levels of MOA and MNA compared with the other genotypes (P < 0.001). At 8 months of age, the wethers had higher levels of MOA and MNA (P < 0.001) than the ewes of the same genotype. There was a strong relationship (P < 0.001) between MOA and MNA and the fat and lean percentage for 22-month-old ewes. Effects of sire, dam and slaughter day (at the same slaughter age) on MOA and MNA were also found. The results suggest that there is good feasibility for selection against animals at risk of possessing higher levels of short branched-chain fatty acids.
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KRAUSGRILL, D. I., N. M. TULLOH, W. R. SHORTHOSE y K. SHARPE. "Effects of weight loss in ewes in early pregnancy on muscles and meat quality of lambs". Journal of Agricultural Science 132, n.º 1 (febrero de 1999): 103–16. http://dx.doi.org/10.1017/s0021859698006133.
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Three successive experiments, of similar design, were carried out during 1986–88 at Mount Derrimut, Australia. Mature Merino ewes were mated to Poll Dorset rams and then allocated to either a control group (C) or a treatment group (R). Ewes from each treatment were slaughtered 60, 70, 100 or 140 days post-conception and the development of their foetuses was compared in terms of body size and muscle characteristics. In Expts 1 and 2, some ewes were allowed to lamb and the progeny in each group were slaughtered after reaching a body weight of 35 kg, for comparison of growth rates, muscle characteristics and meat quality.In each experiment, treatment extended from mating to day 70 of pregnancy and, during this period, both groups were housed. Ewes in group C were kept as one group and fed ad libitum and ewes in group R were individually penned and fed a restricted ration of the same diet as that given to group C in order to achieve a steady loss of body weight. In Expt 1, this loss was 8 kg but, in Expts 2 and 3, feed intake was controlled according to condition score and, during this period, group R ewes lost 25–35% of their body weight at mating. After day 70, all ewes were kept grazing and were offered supplementary feed at rates sufficient for a steady increase in ewe body weights.Foetuses in group R were lower in body weight (P<0·05), crown-rump length (P<0·05) and girth (P<0·01). However, birth weights and mean ages of the 35 kg lambs at slaughter did not differ significantly between treatments.There were no significant differences between treatments for the semitendinosus (ST) and semimembranosus (SM) muscles in total muscle weight, DNA content, protein content, nor in the ratios of muscle weight[ratio ]DNA and protein[ratio ]DNA. However, there were significant differences between experiments, which indicated that cell size in the ST and SM muscles was lower in Expt 2 than in Expt 1.In day 70 foetuses, the cross-sectional area of α fibres was greater (P<0·05) in group R than in group C but by day 140 the difference was no longer significant. At day 70, there was also a positive correlation (r=0·65, P<0·01) between the cross-sectional area of β fibres and the number of α fibres surrounding each of them. There were no significant differences between treatments at any age in the percentages of βR, αR and αW fibres.Meat from group R lambs was more tender than that from group C lambs as indicated by significantly lower means in the SM muscle for adhesion (P<0·01) and Warner–Bratzler Peak Force (WB PF) measurements (P<0·05).Although some effects of nutritional restriction were found, severe feed shortage in early pregnancy in sheep is unlikely to have significant effects on the production of prime lamb meat provided that adequate nutrition is available during late pregnancy and post-natal growth.
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Sakul, Hakan, Martin Dally y Eric Bradford. "Evaluation of Australian merino and U.S. sheep breeds for growth and carcass traits1". Journal of Animal Science 71, n.º 2 (1 de febrero de 1993): 363–68. http://dx.doi.org/10.2527/1993.712363x.
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Brown, D. J. y N. M. Fogarty. "Genetic relationships between internal parasite resistance and production traits in Merino sheep". Animal Production Science 57, n.º 2 (2017): 209. http://dx.doi.org/10.1071/an15469.
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Breeding Merino sheep that are resistant to internal parasites alleviates the high costs associated with treatment of worm infestation and loss of production, as well as mitigating the development of anthelmintic resistance among the major worm species. Faecal worm egg count ((cube root transformation), wec) can be used in sheep as a measure of internal parasite resistance. Accurate estimates of genetic parameters for wec are required for calculation of Australian Sheep Breeding Values and inclusion of worm resistance in sheep breeding programs. This study provides updated estimates of heritability for wec and its genetic correlations with production traits. Data were analysed from a wide range of Australian and New Zealand Merino sheep in the MERINOSELECT database, which included 141 flocks with 801 flock years and up to 217 137 animals with wec recorded in at least one of four ages (W = weaning, P = post weaning, Y = yearling, H = hogget). The heritability estimates ranged from 0.16 ± 0.01 for Ywec to 0.29 ± 0.01 for Wwec, with generally high genetic correlations between the ages. Bivariate analyses estimated genetic correlations between wec at the various ages and growth, carcass quality, reproduction and wool production traits at various ages. These genetic correlations were generally small or close to zero, albeit with some significantly different from zero. The moderate heritability for wec (0.2–0.3) and its high phenotypic variation (coefficient of variation >30%) shows that relatively rapid selection response for worm resistance could be achieved. Inclusion of wec in sheep breeding programs to increase worm resistance would be expected to have little if any impact on other important production traits. These genetic parameters have been incorporated into MERINOSELECT by Sheep Genetics to provide Australian Sheep Breeding Values for wec and appropriate indices for wool and meat production. There is evidence that genotype × environment interactions may be important in some environments by reducing the accuracy of Australian Sheep Breeding Values for wec. Hence it may be prudent for breeders to implement strategies that manage the risk of any impact of genotype × environment on their breeding program.
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Bray, M., D. K. Revell, C. S. Bawden y P. I. Hynd. "Keratin gene expression in Merino sheep with divergent wool growth". Australian Journal of Agricultural Research 56, n.º 3 (2005): 203. http://dx.doi.org/10.1071/ar03253.
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South Australian Merino sheep were selected on the basis of high or low estimated breeding values (EBV) for wool growth rate (W), but with similar bodyweight, follicle density, and mean fibre diameter. Differences in the level of expression of keratin genes were examined in the skin of these sheep to test the hypothesis that divergence in EBV for wool growth is related to the production of wool proteins differing in sulfur (S) content. Further, it was proposed that this differential gene expression would be most pronounced when the supply of S amino acids to the animal was increased. Sheep selected for high EBV (+W) produced more wool per day than low EBV sheep (–W) (on average 32.5 v. 17.7 g/day clean wool, respectively; P < 0.05) but the S content of the wool did not differ between selection groups (2.77% v. 2.87% S, respectively; P = 0.2). Expression of keratin genes including keratin-associated protein KAP 2 (a high S gene), KAP 4 (an ultra-high S gene), KAP 6 (a high glycine/tyrosine gene), and the intermediate filament gene K 2.10, did not differ significantly between +W and –W groups. KAP 2 and K 2.10 each accounted for approximately 5% of the variation in wool growth rate (WGR) but expression of none of the genes examined was significantly related to the S content of the fibre produced. This suggests that differential keratin gene expression was not the source of genetic divergence in WGR. Instead the latter likely reflects a combination of differential cellular rate and growth processes (e.g. rate of bulb cell production, hypertrophy of cortical cells), differences in the relative production of inner root sheath and fibre from the follicle bulb cell population, or differential nutrient uptake into the follicle.
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Foldes, A., J. B. Donnelly, C. A. Maxwell, S. B. James y S. L. Clancy. "Circadian rhythm in wool depilation force in Merino and Merino X Border Leicester sheep". Journal of Agricultural Science 104, n.º 2 (abril de 1985): 397–403. http://dx.doi.org/10.1017/s0021859600044087.
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SummaryAs part of an ongoing investigation of ovine neuroendocrine mechanisms relating to photoperiod and eventually to wool growth, the diurnal variation of depilation force (an index of the strength of attachment of wool fibres to the skin of sheep) was investigated in Merino wethers and Border Leicester Merino ewes. Circadian rhythms were demonstrated in depilation force in both ewes and wethers. Further experiments were performed to investigate circadian endocrine rhythms which may have some bearing on the observed rhythm in depilation force. Circadian rhythms 180° out of phase with the depilation force rhythm were observed in plasma cortisol concentrations and in pineal serotonin N-acetyltransferase activities in Merino wethers.
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Van Beem, D., D. Wellington, B. L. Paganoni, P. E. Vercoe y J. T. B. Milton. "Feed efficiency for meat and wool production by Merino and F1 Dohne×Merino lambs fed pelleted diets of different nutritive value". Australian Journal of Experimental Agriculture 48, n.º 7 (2008): 879. http://dx.doi.org/10.1071/ea08063.
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There is anecdotal evidence from Western Australian breeders that Dohne sheep maintain a higher level of meat and wool production than Australian Merinos. Feed efficiency, carcass and wool attributes are moderately heritable so we hypothesised there would be differences in these traits between Merino and F1 Dohne × Merino lambs. Two groups of 15 Merino and 15 F1 Dohne × Merino wether lambs (29–40 kg) were fed a pelleted diet of either moderate or high energy and protein content for 48 days. Ad libitum pellet intake and liveweight gain were measured and the feed conversion ratio (FCR) for both wool growth and liveweight were calculated. Wool growth and quality were measured and the lambs were slaughtered to measure carcass and meat quality attributes. The F1 Dohne lambs were heavier at the start of the study and grew faster than the Merinos (P < 0.05) irrespective of diet. Consequently, the carcasses of the F1 Dohne lambs were heavier than the Merinos (P < 0.001), but the differences in FCR were not significant. Merino lambs produced more clean wool of lower fibre diameter from less feed than the F1 Dohne lambs (P < 0.05). These results suggest that F1 Dohne × Merino lambs may have an economic advantage in terms of meat production, but this is traded-off against wool production.
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Ash, A. J. y B. W. Norton. "Effect of DL-methionine supplementation on fleece growth by Australian cashmere goats". Journal of Agricultural Science 109, n.º 1 (agosto de 1987): 197–99. http://dx.doi.org/10.1017/s0021859600081168.
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Australian feral goats have recently been found to produce commercially viable quantities of the luxury fibre cashmere (Smith, Clarke & Turner, 1973). Cashmere is the fine down produced by secondary follicles as an undercoat during winter. Fibre diameter ranges from 8 to 24 μm with a mean diameter of 16 μm. Unlike modern breeds of sheep such as the Merino which exhibit almost continuous wool growth, cashmere growth is distinctly seasonal with fibre growth commencing in summer (long daylength) and reaching a maximum length in early winter (short daylength) (McDonald, 1985). The cashmere is cast in spring with growth recommencing again in summer.
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Butler, LG, WR King y CL McDonald. "Growth of young Merino sheep grazing cereal stubbles and supplemented ad libitum with oats, of different crude protein contents, sprayed with various amounts of urea". Australian Journal of Experimental Agriculture 27, n.º 3 (1987): 339. http://dx.doi.org/10.1071/ea9870339.
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In 2 experiments on cereal stubble, growth responses by Merino hoggets and Merino weaners to ad libitum supplementation with oat grain sprayed with a urea-ammonium sulfate solution were examined. In each experiment, 3 batches of oats of different crude protein(CP=7.8,9.3, 11.4 and 7.1, 10.1, 12.5% w/w) were treated with different amounts of urea (0.55-3.2% w/w) and the feed was offered to groups of 10 hoggets or 7 weaners for 70 days and 100 days respectively. The growth of Merino wether weaners grazing wheat stubble was significantly increased from 86 g/sheep.day to 116 g/sheep.day by adding urea to supplements of low protein (7%) oats. The intake of low protein oats sprayed with urea was decreased when urea was added at a level making up 3% of the supplement. Daily growth rates (132-152 g/sheep) of weaner sheep fed oats of 10% and 12.5% crude protein were not significantly different. The addition of urea to these oats did not produce significant additional growth responses. There was no effect on hogget daily growth rate (average = 160 g/sheep) of CP, of the base oat, or of treatment of the oat with a urea-ammonium sulfate mixture.
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Pickering, FS y PJ Reis. "Effects of abomasal supplements of methionine on wool growth of grazing sheep". Australian Journal of Experimental Agriculture 33, n.º 1 (1993): 7. http://dx.doi.org/10.1071/ea9930007.
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Seven experiments are reported in which methionine supplements were given directly into the abomasum of Merino wethers grazing either improved or native pasture at Armidale, New South Wales. In 4 experiments where initial wool growth was 0.4-0.8 mg/cm2.day of clean dry wool, significant increases in wool growth (at 2.4 g methionine/day in 3 experiments and 0.6-4.8 g/day in the fourth) and fibre diameter were obtained when methionine was given once daily in capsules. In the fourth experiment the response to methionine was quadratic, with a maximum at 2.4 g/day. In the remaining 3 experiments, where initial wool growth was >1.1 mg/cm2.day, no significant response to methionine was obtained, whether it was given once daily or infused continuously.
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Aboneev, Vasily, Dmitry Aboneev, Ekaterina Aboneeva, Safarbi Kazanchev y Dastanbek Baimukanov. "Results of using different breed studs in commercial fine wool sheep breeding". E3S Web of Conferences 262 (2021): 02016. http://dx.doi.org/10.1051/e3sconf/202126202016.
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This work presents the material of research and production experiments on the crossing of stud rams of the North Caucasian meat and wool breed and Australian meat merino with fine wool ewes of a commercial herd. It is identified that the use of North Caucasian rams on fine wool ewes serves to increase the fertilizing ability and milk production of the breeding stock, to increase viability and resistance of young animals, as confirmed by the best morphometrical differences of crossbred offspring placentas. Crossbred offspring from semi-fine wool rams had a large live weight at birth at 21 days and at 4 months of age. The use of Australian producers did not have a significant effect on the above indicators of economically useful traits in comparison with purebred breeding.
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Cronin, Greg M., Danai F. Beganovic, Amanda L. Sutton, David J. Palmer, Peter C. Thomson y Imke Tammen. "Manifestation of neuronal ceroid lipofuscinosis in Australian Merino sheep: Observations on altered behaviour and growth". Applied Animal Behaviour Science 175 (febrero de 2016): 32–40. http://dx.doi.org/10.1016/j.applanim.2015.11.012.
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Cake, M. A., M. D. Boyce, G. E. Gardner, D. L. Hopkins y D. W. Pethick. "Genotype and gender effects on sheep limb bone growth and maturation: selection for loin depth causes bone hypotrophy". Australian Journal of Experimental Agriculture 47, n.º 10 (2007): 1128. http://dx.doi.org/10.1071/ea07058.
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This study aimed to compare limb bone growth between offspring of typical crosses used in Australian prime lamb production. Limb bones from sheep of five genotypes – Merino (M × M), Border Leicester sire × Merino (BL × M), Poll Dorset sires selected for growth × Merino (PDg × M), Poll Dorset sires selected for eye muscle depth (PDm × M) × Merino, or second cross (PDg × BLM) – at four time points from 4 to 22 months of age (n = 593) were dissected, measured and weighed. Growth curves were fitted within genotype groups and used to compare (i) overall limb bone growth in terms of length and weight, (ii) differences in allometric growth coefficients for individual bones, (iii) relative limb bone proportions, and (iv) maturity proportion. Results showed two distinct phenotypes in terms of limb bone growth: (i) relative bone hypotrophy of lambs from PDm × M, suggesting that selection for loin depth (PEMD EBV) may be linked with smaller limb size and that their higher muscle : bone ratio may be due to a relative decrease in bone rather than increase muscle weight; and (ii) Merinos were found to have comparable limb length to terminal sire crosses, although distal limb elements were proportionately longer at the expense of the proximal segments that are associated larger muscles. There was a general lack of major differences in bone growth between sheep very different in other production traits, particularly when compared allometrically. Thus, differences in bone growth, proportion or skeletal maturation were greater between ewes and wethers than between these divergent genotypes. PDm × M and BL × M were found to be earlier maturing in terms of limb length, although the bone mineral profile (magnesium content) of PDm × M was suggestive of relative physiological immaturity.
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Lees, A. M., M. L. Sullivan, J. C. W. Olm, A. J. Cawdell-Smith y J. B. Gaughan. "The influence of heat load on Merino sheep. 1. Growth, performance, behaviour and climate". Animal Production Science 60, n.º 16 (2020): 1925. http://dx.doi.org/10.1071/an19687.
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Context Annually, millions of sheep are exported from Australia to the Middle East, typically during the southern hemisphere winter to the northern hemisphere summer. During these voyages, sheep can be exposed to relatively rapid changes in ambient conditions within a short period of time (≤29 days); therefore, excessive heat load concerns can arise. Aims The aim of this study was to define the responses of sheep to incremental heat load under simulated live export conditions. The study herein describes (1) the heat load imposed, and (2) the effect of this heat load on the growth, performance and behavioural responses of sheep during periods of incremental heat load. Methods A total of 144 Merino wethers (44.02 ± 0.32 kg) were included in a 29-day climate controlled study using two cohorts of 72 sheep (n = 2), exposed to two treatments: (1) thermoneutral and (2) hot (HOT). Ambient temperature (°C) and relative humidity (%) for the HOT treatment were modelled from live export voyages from Australia to the Middle East in July. Climatic conditions within the climate control chambers were recorded at 10-min intervals, then used to calculate a temperature humidity index. Sheep posture, rumination, eating, drinking and demeanour (calm, agitated or depressed) were observed four times daily at 3-h intervals between 0800 hours and 1700 hours. Feed intake was recorded daily and water intake was measured using an automated meter. Sheep were weighed on Day 0 and then at 7-day intervals. Sheep were weighed at slaughter and carcass weights were obtained, these data were used to determine carcass dressing percentage. Data were analysed using a repeated measures model, with a compound symmetry covariance structure. Key results Climatic conditions in the HOT treatment increased incrementally between Day 1 (temperature humidity index ≥19) and Day 29 (temperature humidity index ≤34.7). Behaviour, feed intake, average daily gain (g/day), carcass weight (kg) and dressing percentage were not influenced by treatment (P > 0.05). Sheep in the HOT treatment group showed a 137% increase in water intake (P < 0.01) and on average consumed 2.15 L/sheep.day, whereas the thermoneutral group consumed 1.67 L/sheep.day. Conclusions These results suggest that these sheep were capable of maintaining feed intake and growth despite exposure to heat load, albeit with a 137% increase in water intake. Implications These results highlight the resilience of the Australian Merino genotype, as these sheep were capable of maintaining feed intake and growth during exposure to heat load. As the climatic conditions in this study were modelled based on typical live export vessel conditions, these results may suggest that the climatic conditions experienced by sheep during voyages may not be as critical as previously thought.
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Walkom, S. F., A. N. Thompson, E. Bowen y D. J. Brown. "Weaner survival is heritable in Australian Merinos and current breeding objectives are potentially leading to a decline in survival". Animal Production Science 59, n.º 1 (2019): 35. http://dx.doi.org/10.1071/an17151.
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There is little evidence to show that mortality rates during the period after weaning are improving over time in Australian sheep. The average mortality rate of Merino lambs during the post-weaning period has been estimated to be 5.2%. The present study explored the potential for producers to breed for improved survival rates during the post-weaning period and the potential impact this would have on key production traits. A total of 122526 weaner survival (mortality) records were obtained from 18 Merino flocks, between 1989 and 2014, encompassing a wide variety of Australian Merino sheep types and production systems. The heritability of weaner survival from a sire model was estimated to be 0.07 ± 0.01 and was significantly greater than zero. The survival of lambs post-weaning was significantly influenced by weaning weight, with higher survival rates observed in the heavier lambs. The phenotypic relationship with weight indicates that selection for heavier weaning and post-weaning weights, and in turn larger growth rates, will improve survival rates. There is genetic variation in weaner survival not explained by the relationship with weaning weight. Weight-corrected weaner survival was antagonistically genetically correlated with fleece weight. Due to these antagonistic genetic relationships selection based on popular MERINOSELECT indexes is leading to a very small reduction in the survival rate of lambs after weaning through to the post-weaning stage. To prevent a decline in weaner survival, producers are advised to record weaner survival and include it in their breeding objective.
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Shahinfar, S. y L. Kahn. "Machine learning approaches for early prediction of adult wool growth and quality in Australian Merino sheep". Computers and Electronics in Agriculture 148 (mayo de 2018): 72–81. http://dx.doi.org/10.1016/j.compag.2018.03.001.
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Kleemann, DO, RW Ponzoni, JE Stafford, IN Cutten y RJ Grimson. "Growth and carcass characters of the South Australian Merino and its crosses with the Booroola and Trangie Fertility Merino". Australian Journal of Experimental Agriculture 25, n.º 4 (1985): 750. http://dx.doi.org/10.1071/ea9850750.
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South Australian Merino (M) and highly fecund Booroola (B) and Trangie Fertility (TF) Merino strain rams were mated to M ewes to produce M, B x M and TF x M progeny. At 4-5 months of age (24-kg slaughter group), TF x M and M lambs were heavier than B x M lambs (25.3 and 24.8 kg respectively, v. 228 kg). Similar proportional strain differences were observed at 14-1 5 months of age (38-kg slaughter group), except that, in one year, no difference was observed between the M and B x M strains, resulting in a strain x year interaction (P<0.05). When adjusted for age, TF x M carcasses were heavier than those of B x M at the first slaughter and heavier than those of B x M and M strains at the second slaughter. B x M and TF x M strains had the same fat depths and eye muscle areas, when compared at the same age, but B x M had greater fat depths and larger eye muscle areas than TF x M, relative to carcass weight; values for M were less than those of B x M and TF x M, with and without carcass weight as a covariate. Similarly, ranking of the strains did not change for carcass length, leg length and depth of thorax with and without carcass weight as a covariate. Carcasses of M lambs were longer than those of B x M, TF x M being intermediate. No differences were observed among progeny of FF and + + Booroola sires for the 12 variables measured. We conclude that carcasses of B x M and TF x M high fecundity cross Merino strains have greater depths of fat at both the same age and same carcass weight than those of the South Australian Merino, and suggest that the effect of the Booroola F gene on the characters measured is negligible. The implications of the results to the sheep industry are discussed.
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Joy, Aleena, Frank R. Dunshea, Brian J. Leury, Iain J. Clarke, Kristy DiGiacomo, Pragna Prathap, Minghao Zhang y Surinder S. Chauhan. "275 Access to Shade Mitigate Heat Stress and Improves Growth Performance in Lambs During Summer". Journal of Animal Science 99, Supplement_3 (8 de octubre de 2021): 143–44. http://dx.doi.org/10.1093/jas/skab235.263.
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Abstract The objective of the present study was to investigate the effects of provision of shade on behavior, physiology, and growth of Merino lambs exposed to natural Australian summer conditions. Sixty Merino lambs were randomly allocated to either pasture with shade (n = 30;paddock with trees) or a pasture without shade (n = 30;paddock without any trees) for one month during southern-Australian summer (February-2021). Sheep were grazing on the pastures as per standard protocols followed on the farm with ad libitum access to water. Lambs were monitored twice daily between 0900-1000h and 1400-1600h to record their behavior, and physiological parameters were recorded on hot days (environmental temperature (T) >30°C). Behavioral patterns were represented as the proportion of animals doing specific activities in each treatment group. Grazing was the most frequent activity observed in animals during morning measurement (> 60% in both groups). However, high temperature (T > 30°C) decreased grazing behavior in sheep to < 5% in both treatments. Standing behavior was significantly greater (65.2 vs 21.6%; P < 0.05) for animals under non-shade treatment, while lying behavior was more frequent (17.3 vs 76.3%; P < 0.01) in animals having access to shade. Significantly more animals were seeking water troughs (P < 0.05) in the non-shade group (33.2%) compared to the shade group (10.3%). On an average hot day (T >28°C), most lambs in the shade group were seeking shade (P < 0.01), and when the temperature exceeded >32°C, 90% of the lambs were seeking tree shade. Sheep with access to shade exhibited lower (P < 0.01) respiration rate (117breaths/min) and rectal temperature (39.7°C) than non-shade group (151breaths/min;40.2°C). Overall, access to shade improved (P < 0.001) average daily gain (+0.047kg/day) in sheep compared to the non-shade group (-0.028kg/day). In conclusion, our research confirms that providing access to shade is an effective ameliorative strategy to mitigate heat-stress in sheep during summer heatwaves.
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Ponnampalam, E. N., D. L. Hopkins, K. L. Butler, F. R. Dunshea y R. D. Warner. "Genotype and age effects on sheep meat production. 2. Carcass quality traits". Australian Journal of Experimental Agriculture 47, n.º 10 (2007): 1147. http://dx.doi.org/10.1071/ea07001.
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The present study examines carcass quality traits in different genotypes of Australian sheep slaughtered at 4, 8, 14 and 22 months of age. Poll Dorsetgrowth × Border Leicester Merino (PDg × BLM), Poll Dorsetgrowth × Merino (PDg × M), Poll Dorsetmuscling × Merino (PDm × M), Merino × Merino (M × M) and Border Leicester × Merino (BL × M) genotypes were compared. Sires were selected on the basis of growth (PDg, M and BL) and muscle (PDm) using estimated breeding values (EBVs). Approximately 150 mixed sex animals were slaughtered at each age (595 in total for the four slaughters) and carcass quality traits, including hot carcass weight, loin and semitendinosus (ST) muscle weights, GR fat, fat C, rump fat depth and eye muscle area (EMA), were determined at 45 min to 3 days postslaughter. With age, all carcass quality traits increased in magnitude. Merinos produced the lightest and leanest carcasses (P < 0.01) with lowest values in nearly all the carcass quality traits. At 4 and 8 months of age carcass and loin weights, EMA and GR fat measures were greater (P < 0.01) in second-cross PDg × BLM sheep than all other genotypes. However, traits related to muscle content were similar between first- and second-cross Poll Dorset genotypes at 14 and 22 months of age. The BL × M genotype had lower values than the PD × M genotypes for these traits, at all ages. Traits related to carcass fatness showed that sheep with Border Leicester genetics tend to deposit more fat (P < 0.001) in the carcass than those with Merino or Poll Dorset genetics from 14 months of age onwards. Most carcass quality traits did not differ (P > 0.05) between first-cross Poll Dorset genotypes selected for growth or muscling (PDg × M v. PDm × M). Sires with high muscling EBVs are associated more with shorter carcass length than low muscling EBVs. From ~8 months of age, wethers had greater values (P < 0.05) than ewes of the same age for most carcass quality traits related to size and muscle development, but no effect was present for carcass quality traits that were related to fat deposition. It was clear that the carcass weight of M × M at 8 and 14 months were similar to that observed in PDg × BLM at 4 and 8 months, respectively. Loin weights of M × M and BL × M at 13 and 8 months were similar to that weights observed in PDg × BLM at 8 and 4 months of age, respectively. Animals slaughtered to a muscle weight specification will reach the target at a younger age when they have more Poll Dorset than Border Leicester background genetics. Alternatively animals slaughtered at a specified fat score (using fat C or rump fat depth) will reach the specification at a younger age when they have more Border Leicester than Poll Dorset genetics.
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Pethick, D. W., D. L. Hopkins, D. N. D'Souza, J. M. Thompson y P. J. Walker. "Effects of animal age on the eating quality of sheep meat". Australian Journal of Experimental Agriculture 45, n.º 5 (2005): 491. http://dx.doi.org/10.1071/ea03256.
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The aim of this work was to test the effects of animal age on consumer perceptions of sheep meat quality. Experiment 1 tested eating quality scores (tenderness, liking of flavour, juiciness and overall liking) derived from untrained consumers of grilled M. longissimus lumborum (LL) or M. biceps femoris (BF) derived from Merino ewes ranging from 8.5 to 68.5 months of age. The ewes were derived from one farm and all received a pelleted diet (60% hay, 30% lupin grain and 10% barley grain) that sustained growth between 118 and 173 g/day for at least 22 days pre-slaughter. In experiment 2 consumer testing of grilled LL and roasted BF and M. semimembranosis (SM) was conducted on a commercial line of 12-month-old White Suffolk × Merino lambs (0 erupted incisor teeth) v. a line of Merino yearling sheep about 22 months old (with either 2 or 4 erupted incisor teeth). The results of experiment 1 showed a significant effect of muscle (LL>BF, P<0.001) and a cubic effect of animal age on the consumer scores for grilled steaks. The cubic relationship was due to meat from lamb (8.5 months) and hogget (20 months) having higher scores than those of older animals. There was a close relationship between the objective measures of tenderness and the consumer tenderness score (r2 = 0.53, P<0.001). Results of experiment 2 indicated no significant difference between the grilled LL for the crossbred lamb and 22-month-old (2–4 teeth) Merino yearling sheep. However, the consumer scores for the roasted BF and SM were significantly depressed in the 2–4 tooth yearling Merino categories. In conclusion, this work clearly underpins the current Australian definition of lamb, lamb having better eating-quality attributes than older animals with fully erupted permanent incisor teeth, particularly in muscles from across the carcass. However, this work also highlights the eating quality attributes of older sheep (6 or more permanent incisor teeth) particularly for the LL, and suggests that negative influences of flavour associated with older sheep meat are minimal when the product is served in the absence of subcutaneous and intermuscular fat. Finally, the results suggest the possibility of a new ‘yearling’ sheep meat category based on animals in the 2–4-tooth dentition category.
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Barwick, S. A., D. J. Brown, B. R. Cullis, A. K. Bell, T. J. May, M. W. Lollback, I. M. Rogan et al. "The performance of the Border Leicester in Australia". Animal Production Science 61, n.º 1 (2021): 1. http://dx.doi.org/10.1071/an19493.
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Aims We examine the average performance of Border Leicester (BL) flocks that are part of LAMBPLAN, Australia’s sheep performance recording and genetic evaluation system. We also summarise outcomes from the New South Wales Department of Primary Industry’s research on BL improvement, and discuss the performance required for the BL to continue to be a pivotal part of the Australian prime lamb industry. Key results Modest gains have been recorded in the BL in growth since 2000 and faecal egg counts have reduced, suggesting improved worm resistance. The net reproductive rate has slightly improved, while inbreeding continues to increase. In work conducted by the New South Wales Department of Primary Industries, an improved BL flock, encompassing selection for multiple births and a broadening of the breed’s genetic base, had advantages over purebred BLs in many aspects of performance, including a 19.3% advantage in the net reproductive rate. Advantages in fertility were ~5%, litter size ~7% and lamb rearing ability ~5%. BL improved × Merino and (BL improved × BL) × Merino crossbred ewes also had advantages over traditional BL × Merino ewes in their joining performance when joined to Dorset rams. Conclusions Selection in the BL needs to emphasise traits in a manner consistent with their importance to commercial lamb production. Implications Embracing this selection and broadening the BL’s genetic base will assist the BL to maintain its place in the Australian lamb industry.
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Donald, GE, JP Langlands, JE Bowles y AJ Smith. "Subclinical selenium insufficiency. 5. Selenium status and the growth and wool production of sheep supplemented with thyroid hormones". Australian Journal of Experimental Agriculture 34, n.º 1 (1994): 13. http://dx.doi.org/10.1071/ea9940013.
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Fine wool Merino sheep grazed pastures low in selenium (Se) in 2 experiments, and were supplemented with Se and thyroxine (T4) in experiment 1, and with Se, T4, and tri-iodothyronine (T3) in experiment 2. Both experiments ran for 6 months. In experiment 1, 72 sheep with a mean liveweight of 37 kg were given Se by intraruminal pellet and 6 levels of T4 ranging from 0 to 10 mg sodium L-thyroxine as a subcutaneous injection at 14-day intervals. In experiment 2, 36 sheep with a mean liveweight of 24 kg were given Se by intraruminal pellet, and 3 levels of T4 ranging from 0 to 0.4 mg and 3 levels of T3 ranging from 0 to 0.1 mg by subcutaneous injection at weekly intervals. In both experiments wool production and mean fibre diameter were significantly increased by Se supplementation; the increase in clean fleece production was 7 and 32% in experiments 1 and 2, respectively. In experiment 1, T4 increased greasy fleece weight by up to 8% and reduced yield, mean fibre diameter, and liveweight. In experiment 2, T4 reduced fibre diameter. T3 did not significantly affect wool production, wool characteristics, or liveweight. There was no significant interaction between Se and thyroid hormone supplementation in either experiment. Thyroid hormones were used as effectively for wool production by both Se-deficient and Se-sufficient sheep.
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McDowall, M. L., N. S. Watson-Haigh, N. M. Edwards, H. N. Kadarmideen, G. S. Nattrass, H. A. McGrice y P. I. Hynd. "Transient treatment of pregnant Merino ewes with modulators of cortisol biosynthesis coinciding with primary wool follicle initiation alters lifetime wool growth". Animal Production Science 53, n.º 10 (2013): 1101. http://dx.doi.org/10.1071/an12193.
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The economically important characteristics of the adult fleece of Merino sheep, such as increases in clean fleece weight, fibre length, fibre diameter and crimp characteristics are determined during critical phases of fetal development of the skin and its appendages. Genetics plays a major role in the development of traits, but the maternal uterine environment could also influence development. Treatment of pregnant ewes with cortisol and its analogues has previously been shown to produce changes in wool follicle morphology. The aim of this study was to determine the effect of transient manipulation of maternal cortisol status during critical phases of wool follicle initiation and development in utero. From Days 55–65 post-conception, singleton-bearing Merino ewes were treated with metyrapone (cortisol inhibitor) or betamethasone (cortisol analogue). Lambs exposed to metyrapone in utero were born with hairier birthcoats than the control or betamethasone treatment groups (P < 0.05), displayed a 10% increase in staple length and a reduction in crimp frequency for the first three shearings (P < 0.05). Co-expression network analysis of microarray data revealed up-regulation of members of the transforming growth factor-β and chemokine receptor superfamilies, gene families known to influence hair and skin development. These experiments demonstrate that presumptive transient manipulation of maternal cortisol status coinciding with the initiation of fetal wool follicle development results in long-term alteration in fleece characteristics, namely fibre length and fibre crimp frequency. These results indicate it is possible to alter the lifetime wool production of Merino sheep with therapeutics targeted to gene expression during key windows of development in utero.
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Safari, E., N. M. Fogarty, A. R. Gilmour, K. D. Atkins, S. I. Mortimer, A. A. Swan, F. D. Brien, J. C. Greeff y J. H. J. van der Werf. "Across population genetic parameters for wool, growth, and reproduction traits in Australian Merino sheep. 1. Data structure and non-genetic effects". Australian Journal of Agricultural Research 58, n.º 2 (2007): 169. http://dx.doi.org/10.1071/ar06161.
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Accurate estimates of adjustment factors for systematic environmental effects are required for genetic evaluation systems. This study combined data from 7 research resource flocks across Australia to estimate genetic parameters and investigate the significance of various environmental factors for production traits in Australian Merino sheep. The flocks were maintained for several generations and represented contemporary Australian Merino fine, medium, and broad wool bloodlines over the past 30 years. Over 110 000 records were available for analysis for each of the major wool traits, with over 2700 sires and 25 000 dams. Univariate linear mixed animal models were used to analyse 6 wool, 4 growth, and 4 reproduction traits. This first paper outlines the data structure and the non-genetic effects of age of the animal, age of dam, birth-rearing type, sex, flock, bloodline, and year, which were significant with few exceptions for all production traits. Age of dam was not significant for reproduction traits and fleece yield. Generally, wool, growth, and reproduction traits need to be adjusted for age, birth-rearing type, and age of dam before the estimation of breeding values for pragmatic and operational reasons. Adjustment for animal age in wool traits needs to be applied for clean fleece weight (CFW), greasy fleece weight (GFW), and fibre diameter (FD) with inclusion of 2 age groups (2 years old and >2 years old), but for reproduction traits, inclusion of all age groups is more appropriate. For GFW, CFW, and hogget weight (HWT), adjustment for only 2 dam age groups of maiden and mature ewes seems sufficient, whereas for birth (BWT), weaning (WWT), and yearling (YWT) weights, adjustments need to be applied for all dam age groups. Adjustment for birth-rearing type (single-single, multiple-single, multiple-multiple) is appropriate for wool, growth, and reproduction traits. The implications of adjustment for non-genetic effects are discussed.
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Alemseged, Yohannes y Ronald B. Hacker. "Introduction of Dorper sheep into Australian rangelands: implications for production and natural resource management". Rangeland Journal 36, n.º 1 (2014): 85. http://dx.doi.org/10.1071/rj13034.
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The growing popularity of the Dorper breed of sheep potentially may have implications for the ecological sustainability of the semiarid and arid rangelands of southern Australia. The implications are heightened by forecasts of a warming and drying climate in these rangelands, which may in itself place native vegetation under increasing stress. While the Dorper breed of sheep offers important production advantages, little is known from research under Australian conditions about their grazing ecology and management requirements from a natural resource perspective. Key factors identified from this review of literature from other countries include a high fertility and fecundity, a generalist feeding strategy, a high growth rate and a capacity to survive and reproduce under low-rainfall conditions. The wider range of plant species selected by the Dorper compared with the traditional Merino breed of sheep potentially creates both opportunities and risks for rangeland condition. Less selective grazing may reduce pressure on some species but the capacity to harvest sufficient nutrients over a smaller area could concentrate grazing and promote resource degradation. High reproductive efficiency under a wide range of seasonal conditions may lead to more rapid onset of overgrazing and will require close attention to both natural resources and animal marketing if resource degradation is to be avoided.
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Stephenson, RGA, GR Suter y CJ Howitt. "Wool growth responses to DL-methionine administration and factors affecting the value of supplementation". Australian Journal of Experimental Agriculture 31, n.º 4 (1991): 471. http://dx.doi.org/10.1071/ea9910471.
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Wool growth responses to methionine administration were assessed using Peppin Merino wethers on various planes of nutrition. In experiment 1, sheep were fed 700 g/day of lucerne pellets to maintain liveweight. DL-methionine (5.8 g) administered subcutaneously resulted in 0.29 mg/cm2.day (36%) more wool (P<0.01) and a 2.5 �m (15.2%) increase in fibre diameter (P<0.05). In experiment 2, two levels (700 and 1400 g/day) of lucerne pellets were offered, with and without methionine administered subcutaneously (5.8 g). Main treatment analysis indicated a significant (P<0.01) effect of nutrition on wool growth and fibre diameter, with no effect of methionine, except for a reduction (P<0.05) in liveweight gain. Methionine administration was associated with a non-significant increase (39%) in wool growth for the 700 g diet and no change for the 1400 g diet. In experiment 3, two levels (1.75 and 2.5 g/day) of methionine were infused (4 h daily) when sheep were fed a submaintenance ration of Rhodes grass chaff, supplemented with nitrogen and sulfur. Significant (P<0.05) wool growth responses at both levels of methionine infusion were similar, with absolute (0.21 and 0.23 mg/cm2.day) and percentage (52 and 58%) increases for 1.75 and 2.5 g/day methionine treatments, respectively. Methionine administration only increased wool production at nutritional levels of liveweight maintenance or below when wool growth values for control treatments were 0.63,0.59 and 0.40 mg/cm2.day for experiments 1, 2 and 3. Fibre diameters of sheep in untreated groups were 16.4 and 18.8 pm for experiments 1 and 2. These wool growth and fibre diameter values are 25-40% below what might be expected for this strain of Merino. The values of positive correlations between wool growth and fibre diameter were increased with increased nutrition and the administration of methionine in experiment 2. This result and the nil response at high basal wool growth, together with the low potential net return on the cost of methionine, suggest that the use of methionine could be unprofitable.
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Safari, E., N. M. Fogarty, A. R. Gilmour, K. D. Atkins, S. I. Mortimer, A. A. Swan, F. D. Brien, J. C. Greeff y J. H. J. van der Werf. "Across population genetic parameters for wool, growth, and reproduction traits in Australian Merino sheep. 2. Estimates of heritability and variance components". Australian Journal of Agricultural Research 58, n.º 2 (2007): 177. http://dx.doi.org/10.1071/ar06162.
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Precise estimates of genetic parameters are required for genetic evaluation systems. This study combined data from 7 research resource flocks across Australia to estimate variance components and genetic parameters for production traits in the Australian Merino sheep. The flocks were maintained for several generations and represented contemporary Australian Merino fine, medium, and broad wool bloodlines over the past 30 years. Over 110 000 records were available for analysis for each of the major wool traits, and 50 000 records for reproduction and growth traits with over 2700 sires and 25 000 dams. A linear mixed animal model was used to analyse 6 wool traits comprising clean fleece weight (CFW), greasy fleece weight (GFW), fibre diameter (FD), yield (YLD), coefficient of variation of fibre diameter (CVFD), and standard deviation of fibre diameter (SDFD), 4 growth traits comprising birth weight (BWT), weaning weight (WWT), yearling weight (YWT), and hogget weight (HWT), and 4 reproduction traits comprising fertility (FER), litter size (LS), lambs born per ewe joined (LB/EJ), and lambs weaned per ewe joined (LW/EJ). The range of direct heritability estimates for the wool traits was 0.42 ± 0.01 for CFW to 0.68 ± 0.01 for FD. For growth traits the range was 0.18 ± 0.01 for BWT to 0.38 ± 0.01 for HWT, and for reproduction traits 0.045 ± 0.01 for FER to 0.074 ± 0.01 for LS. Significant maternal effects were found for wool and growth, but not reproduction traits. There was significant covariance between direct and maternal genetic effects for all wool and growth traits except for YWT. The correlations between direct and maternal effects ranged from –0.60 ± 0.02 for GFW to –0.21 ± 0.10 for SDFD in the wool traits and from –0.21 ± 0.03 for WWT to 0.25 ± 0.08 for HWT in the growth traits. Litter effects were significant for all wool and growth traits and only for LS in reproduction traits. The mating sire was fitted in the models for reproduction traits and this variance component accounted for 21, 17, and 8% of the total phenotypic variation for FER, LB/EJ, and LW/EJ, respectively. The implications of additional significant variance components for the estimation of heritability are discussed.
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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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Albers, GAA, GD Gray, Jambre LF Le, LR Piper, IA Barger y JSF Barker. "The effect of Haemonchus contortus on liveweight gain and wool growth in young merino sheep". Australian Journal of Agricultural Research 40, n.º 2 (1989): 419. http://dx.doi.org/10.1071/ar9890419.
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Results of three crossover experiments on a total of 1078 Merino lambs were used to estimate the effect of a single infection of 11 000 Haernonchus contortus larvae on liveweight gain, clean wool growth and wool fineness. Estimates were obtained by direct comparison of six groups of infected and matched uninfected iambs under field conditions. Infections were terminated after 5 weeks, at which stage some mortality had occurred and haematocrits had in five out of six cases declined to less than 24%. Over an 8-9 week period, beginning at the time of infection, liveweight gains of infected lambs were reduced by on average 1.29 kg (range 0.83-1.71 kg) amounting to 38% (12-64%) of liveweight gain in uninfected controls. The detrimental effect of infection was most severe towards the end of the infection period. There was a lag phase of 3-6 weeks between larval administration and the onset of wool growth depression. The reduction of wool growth persisted for at least 14 weeks after termination of infection. The size of this reduction was very variable. Over a 4 month post-infection period, reductions ranged from 11 to 97 g clean wool (mean 46 g) or 1.4 to 157% (mean 6.8%) of clean wool grown by uninfected lambs. Estimates of reduction of fibre diameter over the same period ranged from 0.39 to 0.79 8m (mean 0.57 8m).
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Adams, N. R., S. M. Liu, J. R. Briegel y M. J. Thompson. "Plasma insulin concentrations and amino acid turnover in Merino sheep with high or low fleece weight". Australian Journal of Agricultural Research 55, n.º 8 (2004): 833. http://dx.doi.org/10.1071/ar04076.
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Although sheep with a relatively high fleece weight have reduced fat deposition and a lower reproductive rate, research has failed to identify any specific metabolic demand that growing a fleece places on the physiology of the sheep. This paper reports two experiments in which the effect of fleece weight was examined in ewes infused intravenously with amino acids. The first experiment was carried out when the ewes were 107 days pregnant, and the second 2 years later in non-pregnant ewes from the same flock. The ewes were derived initially from groups that differed in staple strength, but there was no effect of staple strength group on the characteristics measured in either experiment. In Expt 2, ewes were also infused with a bolus of l-[ring-d5] phenylalanine, and the enrichment in plasma determined by GC/mass spectrometry over the next 24 h. In both experiments, fasting plasma insulin concentrations were lower (P < 0.05) in ewes with a high fleece weight, and this difference continued during infusion in Expt 2 (P < 0.05). In Expt 1, infusion of ewes with amino acids resulted in higher (P < 0.05) plasma concentrations of α-amino nitrogen (indicating amino acids) in the ewes with a higher fleece weight, and in Expt 2, ewes with a high fleece weight had a 19% higher rate of appearance of endogenous phenylalanine (P < 0.05). We conclude that sheep with high wool growth rates have higher whole-body protein turnover rate, which may be achieved in part by lower insulin concentrations. Lower insulin in turn provides a mechanism through which wool growth rate may influence energy availability to other tissues.
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Steel, J. W. "Effects of protein supplementation of young sheep on resistance development and resilience to parasitic nematodes". Australian Journal of Experimental Agriculture 43, n.º 12 (2003): 1469. http://dx.doi.org/10.1071/ea03004.
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The influence of dietary protein content, particularly the supply of metabolisable protein, on immunocompetence and on resilience to pathogenic effects during continuous exposure of young sheep to infective larvae is reviewed for the most important abomasal and small intestinal nematodes infecting young sheep in Australian grazing systems. In lambs infected with Haemonchus contortus supplementary protein improves both development of immunity and resilience in breeds of sheep that are susceptible to haemonchosis, but in relatively resistant breeds dietary supplementation appears unnecessary. Recent studies indicate that the increased protein requirements of Merino weaners parasitised by H. contortus would be met by diets containing about 190 g crude protein/kg dry matter, depending on the rumen degradability of the dietary protein source and level of feed intake. Some evidence exists for an enhanced immune response to Teladorsagia circumcincta in lambs receiving an increased supply of protein at the intestines.Response to protein supplementation of lambs infected with Trichostrongylus colubriformis depends on the metabolisable protein content of the basal diet and on the period of exposure to incoming larvae. Where the basal diet only meets requirements for maintenance or low growth rates, increased supply of rumen undegradable protein enhances immune expression in terms of reducing faecal egg count and expelling adult worms, but does not appear to limit the initial establishment of incoming larvae. Effects on growth rate and wool production are most pronounced during the period of worm expulsion, indicating that this phase of the immune response competes with production when nutrient resources, and particularly protein, are limited.Field trials in the Armidale region have shown that supplementation with protein meals of Merino weaners, exposed to natural infection from pasture, can reduce faecal egg count and improve resilience in terms of both growth rate and wool production. These effects may persist for some time after supplementation ceases. Further work is needed to determine the generality of these responses in other sheep-producing regions and genotypes and to establish cost-effective supplementation strategies.
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Coombe, JB, A. Axelsen y H. Dove. "Rape and sunflower seed meals as supplements for sheep grazing cereal stubbles". Australian Journal of Experimental Agriculture 27, n.º 4 (1987): 513. http://dx.doi.org/10.1071/ea9870513.
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In 2 experiments, Merino sheep aged about 18 months grazed cereal stubbles for 12 weeks and were either: (i) given no supplement; (ii) given free access to blocks containing 30% urea; or received daily about 300 g DM sheep-1 of (iii) rapeseed meal (RSM); (iv) formaldehyde-treated RSM (FRSM); (v) sunflower meal (SFM); or (vi) formaldehyde-treated SFM (FSFM). In experiment 1, wethers grazed a barley stubble at stocking rates (SR) of 18 and 36 sheep ha-1, and in experiment 2, mixed flocks of wethers and ewes grazed wheat stubble at 10 and 20 sheep ha-1. Mean daily intakes of urea were about 8.5 and 11.5 g sheep-1 for experiments 1 and 2 respectively. Both forms of SFM were readily eaten throughout, but in both experiments, intakes of RSM and FRSM were low and were characterised by high variability from day to day, and among individual sheep within groups. In both experiments, all sheep gained some weight during the first 2-3 weeks; thereafter control and urea fed sheep lost weight at mean rates varying from about 96 to 180 g day-1 depending on SR. Feeding SFM or FSFM reduced this loss to about 20 g day-1 at SR of 10-20 ha-1, and to 60 g day-1 at a SR of 36 ha-1, while losses were intermediate in sheep fed RSM or FRSM. In experiment 1, daily wool growth rates varied from about 5.5 g clean dry wool (CDW) sheep-1 for control and urea-fed sheep to about 11 g CDW sheep-1 for sheep fed SFM and FSFM; respective daily rates in experiment 2 were 3.6 and 8.2 g CDW sheep-1. Wool growth of sheep fed RSM and FRSM was intermediate in both experiments. When ewes were mated on high-quality feed after grazing stubbles, conception was delayed for about 14 days in a high proportion (about 40%) of those ewes that had lost considerable weight during stubble grazing. This effect was overcome by feeding daily 300 g DM sheep-1 of SFM for 7 days prior to and during mating. Delayed conception extended the lambing period. although final numbers of lambs born were not different among groups.
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Cottle, DJ. "Effects of cottonseed meal, methionine analogues and avoparcin on the wool production of young, grazing wethers". Australian Journal of Experimental Agriculture 28, n.º 6 (1988): 713. http://dx.doi.org/10.1071/ea9880713.
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A series of experiments were conducted which aimed to develop a feed supplement that was more cost-effective at increasing wool growth in sheep than those currently available commercially. In experiment 1, young wethers grazing cereal stubble for 1 month were offered ad lib. blocks containing sorghum, urea and sodium bentonite (buffered Goldenpro, average intake 66 g/day), ad lib. blocks containing molasses, lupins and urea (Ultrapro 30, average intake 52 g/day), or pellets containing cottonseed meal (CSM, 50 g/day) plus hydroxymethyl- methionine (MEP, 3 g/day). Changes in liveweight were similar in all sheep fed supplements but liveweight losses in unsupplemented wethers were significantly (P<0.05) higher than in supplemented wethers. In experiment 2, supplementation of Merino weaners grazing ryegrass-subterranean clover pastures with 37.5 g/day of a pellet containing CSM plus MEP (plus vitamins and minerals) for 3 months resulted in increases in wool growth (+ 7%) and liveweight gain (+38%) compared with wethers fed control (vitamins plus minerals) pellets. In experiment 3, Merino hoggets grazing a ryegrass-subterranean clover pasture were rotationally supplemented for four 6-week periods with 37.5 g/day of CSM plus methionine hydroxy analogue (MHA), CSM plus avoparcin (AV), CSM plus MHA plus AV and 12.5 g/day of control pellets. The sheep grew 11, 18 and 12% more clean wool respectively when fed CSM plus MHA, CSM plus AV and CSM plus MHA plus AV compared with control pellets. The additional wool grown in response to the CSM plus AV pellet was valued at approximately twice the cost of the pellets. Although economic responses to supplementation were obtained, the response levels were well below those obtained in post-ruminal, amino acid infusion studies and conflict with data from pen-feeding experiments.
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Granleese, T., S. A. Clark, A. A. Swan y J. H. J. van der Werf. "Increased genetic gains in multi-trait sheep indices using female reproductive technologies combined with optimal contribution selection and genomic breeding values". Animal Production Science 57, n.º 10 (2017): 1984. http://dx.doi.org/10.1071/an15440.
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Female reproductive technologies such as multiple ovulation and embryo transfer (MOET) and juvenile in vitro fertilisation and embryo transfer (JIVET) can produce multiple offspring per mating in sheep and cattle. In breeding programs this allows for higher female selection intensity and, in the case of JIVET, a reduction in generation interval, resulting in higher rates of genetic gain. Low selection accuracy of young females entering JIVET has often dissuaded producers from using this technology. However, genomic selection (GS) could increase selection accuracy of candidates at a younger age to help increase rates of genetic gain. This increase might vary for different traits in multiple trait breeding programs depending on genetic parameters and the practicality of recording, particularly for hard to measure traits. This study used both stochastic (animals) and deterministic (GS) simulation to evaluate the effect of reproductive technologies on the genetic gain for various traits in sheep breeding programs, both with and without GS. Optimal contribution selection was used to manage inbreeding and to optimally assign reproductive technologies to individual selection candidates. Two Australian sheep industry indexes were used – a terminal sire index that focussed on growth and carcass traits (the ‘Lamb 2020’ index) and a Merino index that focuses on wool traits, bodyweight, and reproduction (MP+). We observed that breeding programs using artificial insemination or natural mating (AI/N) + MOET, compared with AI/N alone, yielded an extra 39% and 27% genetic gain for terminal and Merino indexes without GS, respectively. However, the addition of JIVET to AI/N + MOET without GS only yielded an extra 1% genetic gain for terminal index and no extra gain in the Merino index. When GS was used in breeding programs, we observed AI/N + MOET + JIVET outperformed AI/N + MOET by 21% and 33% for terminal and Merino indexes, respectively. The implementation of GS increased genetic gain where reproductive technologies were used by 9–34% in Lamb 2020 and 37–98% in MP+. Individual trait response to selection varied in each breeding program. The combination of GS and reproductive technologies allowed for greater genetic gain in both indexes especially for hard to measure traits, but had limited effect on the traits that already had a large amount of early age records.
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Hollema, Baukje L., Piter Bijma y Julius H. J. van der Werf. "Sensitivity of the breeding values for growth rate and worm egg count to environmental worm burden in Australian Merino sheep". Journal of Animal Breeding and Genetics 135, n.º 5 (11 de julio de 2018): 357–65. http://dx.doi.org/10.1111/jbg.12349.
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Thompson, J. M. y J. R. Parks. "Food intake, growth and body composition in Australian Merino sheep selected for high and low weaning weight. 3. Energy balance". Animal Science 40, n.º 1 (febrero de 1985): 85–91. http://dx.doi.org/10.1017/s0003356100031871.
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ABSTRACTUsing a simplified energy balance equation, changes in energetic efficiency and energy expenditure were examined as a function of stage of maturity in rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock.Specific combustion energy of the body (i.e. MJ/kg of body weight) was an increasing linear function of stage of maturity, which increased at a slightly faster rate in the weight-minus than in the weight-plus animals (15·1 v. 13·1 MJ/kg per unit of maturity), and at a faster rate in ewes than in rams (17·2 v. 11·3 MJ/kg per unit of maturity). At maturity, all strains had a similar mean specific combustion energy (18·3 MJ/kg), whereas the ewes were greater than the rams (20·1 v. 16·6 MJ/kg).Thermochemical efficiency (TCE, defined as the gain in body energy per unit of metabolizable energy intake) was a quadratic function of stage of maturity. In the early post-weaning period, the weight-plus had a greater TCE than the weight-minus animals and the maximum TCE occurred at an earlier stage of maturity in the weight-plus than in the weight-minus animals (0·40 v. 0·45 maturity). The ewes had a higher TCE than the rams at all stages of maturity, although the differences decreased as the animals matured. The maximum TCE occurred at a later stage of maturity in the ewes than in the rams (0·46 v. 0·38 maturity).After scaling for differences in mature size there was little difference between the strains in the rate of energy expenditure, with the exception that at the later stages of maturity the weight-minus animals had a slightly greater rate of energy expenditure. After scaling for differences in mature size, the rams had a greater rate of energy expenditure than the ewes from weaning to maturity.
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Kashani, Arash, Benjamin William Behrens Holman, Peter David Nichols y Aduli Enoch Othniel Malau-Aduli. "Effect of Level of Spirulina Supplementation on the Fatty Acid Compositions of Adipose, Muscle, Heart, Kidney and Liver Tissues in Australian Dual-Purpose Lambs". Annals of Animal Science 15, n.º 4 (1 de octubre de 2015): 945–60. http://dx.doi.org/10.1515/aoas-2015-0037.
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Abstract This study investigated the effect of level of Spirulina supplementation on the fatty acid (FA ) compositions of subcutaneous adipose, longissimus dorsi muscle, kidney, heart, and liver tissues in purebred and crossbred Australian Merino sheep. Forty-eight lambs sired by Black Suffolk, White Suffolk, Dorset and Merino rams were assigned into 4 treatment groups of daily Spirulina supplementation levels per lamb of 0 mL (control), 50 mL (low), 100 mL (medium) and 200 mL (high) referred to as 0, 5, 10 and 20% groups. The lambs were slaughtered after 9 weeks of supplementation and heart, kidney, adipose, liver and muscle tissue samples were collected. The results demonstrated significant variations in growth and body conformation traits and tissue and organ FA composition in response to the Spirulina supplementation. The medium-level Spirulina treatment group increased the ω-3 and ω-6 polyunsaturated fatty acid (PUFA ) composition in all tissues and organs significantly. The results suggest the use of medium level (100 mL/head/day) of Spirulina supplementation in order to increase lamb production with more ω-3 and ω-6 PUFA and therefore higher nutritional meat quality.
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Perry, Diana, J. M. Thompson y R. M. Butterfield. "Food intake, growth and body composition in Australian Merino sheep selected for high and low weaning weight 6. Muscle-weight distribution". Animal Science 47, n.º 2 (octubre de 1988): 275–82. http://dx.doi.org/10.1017/s0003356100003366.
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ABSTRACTThe change in muscle-weight distribution from birth to maturity was examined in rams and ewes from strains of Australian Merino sheep which had been selected for high or low weaning weight, and from a randomly bred control flock. The proportional distribution of total muscle weight among nine anatomically standardized muscle groups was determined for 34 mature animals. The growth of each group was then assessed relative to the growth of the total musculature, using data from 106 immature animals. Maturity coefficients were calculated separately for pre- and post-weaning growth. Several muscle groups exhibited a diphasic growth pattern.Selection for high and low weaning weight resulted in an increase and decrease respectively in total muscle weight in mature animals, but had no effect on mature muscle-weight distribution. There were no significant strain effects on maturing patterns of muscle groups, except during the pre-weaning growth of muscles around the spinal column and those connecting the thorax to the forelimb. When compared at the same stage of maturity there was little difference between the strains in muscle-weight distribution. However, at the same weight the larger mature-size strain had a more immature pattern of muscle-weight distribution.The total muscle weight of mature rams was greater than that of mature ewes. Sex also had an effect on muscle-weight distribution at maturity for seven of the nine muscle groups. At maturity rams had a higher proportion of their muscle weight in those muscle groups associated with the neck and thorax, and a lower proportion in those associated with the limbs. Sex affected the pre-weaning maturing pattern of the muscles of the spinal column, and the post-weaning maturing pattern of all muscle groups, with the exception of those muscles associated with the distal hindlimb, the spinal column, and those attaching the thorax to the forelimb.
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Lee, GJ y AJ Williams. "Relationship of feed intake with cystine availability and wool growth in Merino wethers". Australian Journal of Agricultural Research 44, n.º 5 (1993): 973. http://dx.doi.org/10.1071/ar9930973.
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Two experiments were conducted to characterize the relationship between nutrient supply and the rate of wool growth. We concentrated on the accepted view that the rate of wool growth in Merino sheep is primarily limited by the availability of sulfur amino acids, which are largely determined by diet intake and its interaction with microbial fermentation in the reticulo-rumen. In the first experiment, the effects of variable intakes of two diets (one including 10% fishmeal) by sheep on the rate of irreversible loss of cystine and plasma cystine concentration were investigated. Nitrogen intake (N) was positively and linearly related to both the irreversible loss rate and the plasma concentration of cystine, with no effects of diet per se. In the second experiment, the same dietary treatments were imposed on 39 wethers for 16 weeks following an 8 week pre-experimental period. The monthly rates of wool growth, average fibre diameter and sulfur content of the wool were measured and related to various components of intake. The rate of wool growth responded in a positive curvilinear decreasing manner to changes in intake, the response requiring 2 months to stabilize. There was no significant effect of diet when daily intake was expressed as g N kg-0.75 liveweight. Including the covariate (wool growth when fed the standard diet), the quadratic linear model accounted for 90% of the total variation in wool growth. Responses in fibre diameter and its variation, and wool sulfur content were similar to those of wool growth, in that they were positive and did not equilibrate quickly. A saturation kinetics model of the relationship between daily N intake (g N kg 0.75 liveweight) and wool growth accounted for a similar proportion of the variation as did a linear (with quadratic term) model without the covariate. It is concluded that the saturation kinetics model may be useful for more comprehensive comparisons of both the genetic potential and the sensitivity of wool growth to environmental changes.
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Bencini, R., T. W. Knight y P. E. Hartmann. "Secretion of milk and milk components in sheep". Australian Journal of Experimental Agriculture 43, n.º 6 (2003): 529. http://dx.doi.org/10.1071/ea02092.
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The effect of milking intervals of 4–20 h and of milking frequencies of 1–6 times a day on the rate of secretion of milk and milk components was determined in 2 breeds of sheep unselected for dairy production, the Australian Merino and the New Zealand Poll Dorset. The rate of milk secretion was greater after short intervals and after increased milking frequencies, indicating that in sheep the rate of milk secretion in the short term is regulated by a local feedback mechanism. After short intervals between milkings, the fat concentration in the milk was higher (99.5 ± 6.21 g/kg) and the protein concentration was lower (about 65 ± 2.89 g/kg) than after long intervals between milkings. This was not due to the presence of residual milk left in the mammary glands as subsequent experiments gave similar results when the residual milk was removed with the aid of oxytocin. We obtained similar responses if ewes were exposed to a series of 4 consecutive milkings to remove possible carry-over effects of the previous interval and achieve a constant volume of residual milk. We concluded that in sheep the rate of secretion of fat decreases while that of protein increases with time after milking and that the synthesis of fat and protein are controlled by at least 2 different mechanisms. This might be due to the fact that, unlike dairy cows and goats, sheep have not been subjected to selective pressure for dairy production.
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Thompson, J. M., J. R. Parks y Diana Perry. "Food intake, growth and body composition in Australian Merino sheep selected for high and low weaning weight. 1. Food intake, food efficiency and growth". Animal Science 40, n.º 1 (febrero de 1985): 55–70. http://dx.doi.org/10.1017/s0003356100031858.
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ABSTRACTChanges in the pattern of food intake, food conversion efficiency and growth from weaning to maturity, were examined in 35 rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock. The sheep were individually fed a pelleted ration ad libitum for at least 72 weeks and up to 90 weeks post weaning. Weekly food intake was described as an increasing exponential function of age with a linearly declining asymptote, about which a regular oscillation occurred, and weekly body-weight gain was described as an increasing exponential function of weekly food intake, about which a regular oscillation also occurred.The oscillations in weekly food intake had a period of about 52 weeks and appeared to be largely associated with seasonal variations in temperature, with an increased food intake during winter and a decreased food intake during summer. The oscillations in both the food-intake and body-weight functions were of similar phase and period and it was suggested that the body-weight oscillations were due to variation in gut-fill, a result of the seasonal oscillations in food intake.Selection for weaning weight changed the shape and magnitude of the food-intake curve, with the weight-plus having a greater rate of food intake (i.e. appetite) in the early stages of growth and a greater asymptote than the weight-minus animals. Selection for high and low weaning weight also resulted in an increase and a decrease in mature weight. Both strains had a similar growth efficiency, although when calculated as gross food conversion efficiency the weight-plus were higher than the weight-minus animals at the same body weight, whereas there was no difference between strains at the same age.The rams had both a higher asymptote and a slower rate of decline in food intake than the ewes. Rams had a higher mature weight than the ewes, although ewes had a slightly greater growth efficiency. However, when calculated as gross food conversion efficiency, ewes tended to be lower than rams, when compared either at the same age, or at the same body weight.When the food-intake curves were standardized for differences in mature size, strain differences in the magnitude of the food-intake curves were reduced, although differences in the shape were still apparent. Shape differences in the food-intake curves were reflected in the shape of the standardized growth curves, with the weight-plus maturing at a faster rate than the weight-minus animals. There was little difference between the sexes in the initial shape of the food-intake curve, although at later ages ewes had a lower food intake than rams. There was little difference between the sexes in the shape of the standardized growth curves.
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Mulholland, JG y GK Preston. "A comparison of buckwheat, oats, and wheat for the maintenance of liveweight and wool production in sheep". Australian Journal of Experimental Agriculture 35, n.º 3 (1995): 339. http://dx.doi.org/10.1071/ea9950339.
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Merino wethers about 2 years old were confined in pens and fed, daily or weekly, maintenance rations of whole buckwheat, crushed buckwheat, whole wheat, or oats. All rations were supplemented with a small portion of pasture hay and minerals and were compared for acceptance, digestible energy (DE), and wool growth. The DE of the ration containing whole buckwheat was 13.1 MJ/kg DM and was 86.3% of the DE value of the wheat ration and 11% higher than that of oats, but the oats were below average Australian quality. Processing buckwheat increased faecal energy loss and reduced DE by 8%. During the first 10 days of feeding, the sheep fed weekly lost 75 day compared with a gain of 6 g/day for the daily-fed group, but thereafter liveweights remained fairly constant. This resulted in an overall difference (P<0.05) between weekly and daily feeding. Significantly (P<0.05) higher food refusals were obtained with weekly feeding, but there was no difference between grain types. Wool growth was similar for all grains and for daily and weekly feeding. It was concluded that buckwheat is a suitable grain for maintaining liveweight and wool production of sheep.