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1
Hall, DG, AR Gilmour y NM Fogarty. "Variation in reproduction and production of Poll Dorset ewes". Australian Journal of Agricultural Research 45, n.º 2 (1994): 415. http://dx.doi.org/10.1071/ar9940415.
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Poll Dorset ewes were joined to Booroola Merino (n = 22) or Trangie Fertility Merino (n = 26) rams in single sire joinings during late summer/autumn of 1978, 1979, 1980 and 1981. Rams were changed each year and there were 1678 individual ewe joinings. A maximum of 527 ewes were used in any one year, and they represented 14 studs and varied in age, reproductive history and liveweight. The traits, litter size, maternal lamb survival, lambs weaned per ewe lambing and weight of lamb weaned per ewe lambing (kg at 100 days) were analysed for the effect of year, stud, age, lambs born and ewe liveweight. Litter size averaged 1-37, maternal lamb survival 0.70, and number of lambs weaned per ewe was 0.94. There were large variations in the reproductive traits due to year and stud and lesser effects due to age. Each extra kilogram of ewe liveweight at joining increased litter size by 0.012 and weight of lamb weaned by 0.39 kg, but had no significant effect on maternal lamb survival or number of lambs weaned. Multiple-bearing ewes weaned 0.72 more lambs and 16 - 2 kg more lamb weight than single-bearing ewes. Lamb survival was similar for singleand multiple-bearing ewes. Greasy fleece weight averaged 2.2 kg ewe-' and single bearing ewes produced 0.19 kg/ewe more than multiple-bearing ewes. Dystocia caused 53% and starvation/mismothering/exposure caused 23% of lamb deaths; the proportion of deaths due to starvation/mismothering/exposure increased with increasing ewe joining liveweight. The large variation between studs in reproductive performance partly reflected genetic differences between Poll Dorset flocks which could be exploited. Estimates of heritabilities ranged from 0.06 to 0.14 � 0.10 for the reproductive traits and were 0.10 � 0.12 for ewe liveweight and 0.16 � 0.20 for greasy fleece weight. However much of the between stud variation may also have arisen from early environmental effects. Estimates of repeatability ranged from 0.06 to 0.l5 � 0 05 for reproduction traits and were 0.44 � 0.06 for ewe liveweight at joining and 0.56 � 0.08 for greasy fleece weight.
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Pattinson, S., D. A. R. Davies y A. Winter. "Colostrum and lamb production of prolific ewes". BSAP Occasional Publication 15 (1992): 166–68. http://dx.doi.org/10.1017/s0263967x00004195.
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The prolific ewe can be regarded as a valuable asset only if she produces viable lambs and, at the same time, sufficient colostrum to meet their needs for energy (MJ) and immunoglobulin (Ig) in the first days of life.The energy requirements of the lamb will depend on its weight and the climatic conditions of its surroundings. Mellor and Murray (1986) recommend 180 ml colostrum per kg body weight during the first 18 h of life for lambs born indoors and 210 ml/kg body weight for lambs born in field conditions. The Ig requirement of the lamb will depend on its size and the disease challenge of the environment into which it is born.Although lower immunoglobulin G (IgG) levels have been recorded in dead lambs compared with live lambs (Halliday, 1968 and 1978; Khalaf, Doxey, Baxter, Black, FitzSimons and Ferguson, 1979), it has been shown that many lambs having low serum IgG levels do survive (Halliday, 1974) and some with high levels die (Halliday, 1978).The minimum intake of colostrum required for passive immunity is not known, but it is probably considerably less than that needed to meet the energy requirements (Mellor and Murray, 1986). Spedding, Treacher and Penning (1970) showed that as little as 8 g colostrum per kg lamb birth weight can provide protection from disease. Under poor conditions of hygiene this would probably not be sufficient. It thus seems likely that provided that the energy requirement of the lamb is met by feeding it colostrum, the Ig requirement will also be met.
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Lambe, N. R., M. J. Young, G. Simm, J. Conington y S. Brotherstone. "Seasonal tissue changes in Scottish Blackface ewes over multiple production cycles". Proceedings of the British Society of Animal Science 2003 (2003): 4. http://dx.doi.org/10.1017/s1752756200011637.
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A previous study using X-ray computed tomography (CT) of Scottish Blackface hill ewes found that carcass fat, internal fat and muscle are depleted during pregnancy and early lactation and deposited during late lactation and the dry period. Relationships were also found between fat and muscle levels and lamb production traits (Lambe et al., 2002a). Changes in tissue levels over multiple production cycles of the hill ewe, and how these changes relate to lamb production are also of interest. The aims of this study were to model changes in carcass fat, internal fat and muscle through three production cycles and to compare patterns of tissue change in ewes producing different numbers of lambs.
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Adeleye, I. O. A. "SEASONAL EFFECTS ON LAMB PRODUCTION UNDER TROPICAL CONDITIONS". Nigerian Journal of Animal Production 11, n.º 2 (15 de enero de 2021): 168–74. http://dx.doi.org/10.51791/njap.v11i2.2548.
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Observations were made over a period of three years on a total of 336 West African Dwarf (WAD) ewes that were mated to four rams in rotation. Out of a total of 753 lambs obtained, 459 (61%) were produced in the wet season as compared to 294 (39%) produced in the dry season. More lambs were produced as a result of multiple birth (twins and triplets) in the wet than in the dry season. Consequently, the average birth weight of the wet season lambs (1.58kg) was lower than the average birth weight (1.66 kg) of the dry season lambs. Despite this initial disadvantage, the wet season lambs had a higher average weaning weight (9.11 kg) than the dry season lambs (7.83 kg). The effects of season on pre weaning lamb mortality was minimal while the effects of type of birth were quite apparent. Lowest pre-weaning lamb mortality values were recorded for single lambs, followed by twins and triplets, in ascending order. The data also showed that a slightly higher proportion of the male lambs reached weaning age than female lambs. This observation could be associated with reported inverse relationship between lamb birth weight and mortality found in literature.
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Freer, M., JR Donnelly, A. Axelsen, H. Dove y DG Fowler. "Prime lamb production in relation to time of mating". Australian Journal of Experimental Agriculture 34, n.º 1 (1994): 1. http://dx.doi.org/10.1071/ea9940001.
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Over 3 years, we examined the possible benefits of moving the joining date from mid March to early February for the productivity of a prime lamb system based on Border Leicester x Merino ewes on the southern tablelands of New South Wales. The proportion of ewes with >1 lamb (fertility) was affected more by year and by age of ewe than by joining date. The mean proportion of fertile ewes with >1 lamb (fecundity) was reduced from 0.28 to 0.15 at the earlier date, while immunisation against androstenedione increased fecundity at both mating times to 0.42 but significantly reduced fertility in the earlier group. Over the 3 years, the earlier joining produced 12 fewer lambs per 100 ewes mated and immunisation increased lamb number by 17, but flushing (for 3 weeks with sunflower meal) had no significant effect. Immunisation did not have a consistently greater effect at the earlier joining. Groups of these ewes, balanced for fetus number, grazed at 6.5, 10, or 13 per ha on pastures based on phalaris and subterranean clover. Ewe liveweight after lambing, lamb birth weight, and perinatal mortality were not affected by joining date, but mean daily weight gain by later born lambs over the first 90 days of life was 44 g greater than for earlier born lambs. However, earlier joining enabled 17 more lambs per 100 ewes to reach a marketable weight of 31 kg within the pasture season. Twins grew more slowly and relatively few reached sale weight. With a mean 1.4 lambs per ewe, the optimum stocking rate on these pastures appeared to be 6.5-10 ewes/ha. Superphosphate application to half of the experimental area, after 17 years without treatment, increased pasture weight, lamb growth rate, and numbers sold. The increase was such that a treated pasture could have carried an extra 3 ewes/ha without depression in individual productivity, relative to an untreated pasture. Supplementation of ewes in late pregnancy and early lactation benefited only twin lambs at the higher stocking rates. The results suggest that a prime lamb system in this environment is more likely to succeed with the earlier joining date. The lower lambing percentage, resulting from a decrease in fecundity, is likely to be of benefit, rather than detriment, to the efficiency of a system in which single- and twin-bearing ewes and their lambs are given equivalent treatment.
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Giro, Tatiana, Andrey Kulikovsky, Svetlana Andreeva, Ivan Gorlov y Anna Giro. "Production of enriched lamb in biodegradable packaging". Foods and Raw Materials 8, n.º 2 (30 de septiembre de 2020): 312–20. http://dx.doi.org/10.21603/2308-4057-2020-2-312-320.
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The paper describes an environmentally safe technology for biofortifying lamb with target components in required concentrations packed in biodegradable film. To address the problem of micronutrient deficiency, we developed a biologically safe method of enriching lamb with organic iodine and selenium supplements. Introducing selenium and iodine feed supplements to the animals’ diet increased the average daily growth of their live mass in experimental groups by 3.43, 6.72, and 14.92% in groups I (iodine), II (selenium), and III (iodine and selenium), respectively, compared to the control group (feed only). The analysis of immunephysiological status showed an increase in phagocytic number in experimental groups: by 5.1% (P > 0.95), 9.4%, and 14.5% in groups I, II, III, respectively. In addition, the highest phagocytic activity and phagocytic intensity were observed in animals of group II and group III, indicating their higher resistance to adverse environmental factors, compared to the control. There was an increase in iodine, selenium and zinc content in the lamb meat from the experimental groups grown on enriched diets. We recorded a higher concentration of the micronutrients in the lambs receiving “Yoddar-Zn” and “DAFS-25” supplements together (Zn – 980 μg/100 g; Se – 53.9 μg/100 g; I – 77.6 μg/100 g). We found that the contents of zinc, selenium, and iodine in 100 g of m. Longissimus dorsi were 8.2%, 77.0%, and 51.7%, respectively, of the required content in the daily diet. Thus, we can use this raw material to produce functional meat products. Packaging lamb in sodium alginate-based biodegradable film helped reduce moisture loss during storage.
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Hall, DG, LR Piper, AR Egan y BM Bindon. "Lamb and milk production from Booroola ewes supplemented in late pregnancy". Australian Journal of Experimental Agriculture 32, n.º 5 (1992): 587. http://dx.doi.org/10.1071/ea9920587.
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Booroola ewes in moderate body condition on pasture, were either not supplemented, or supplemented prior to parturition with lupin grain for 9 days in a preliminary experiment, or with lupin or oat grain for 17 days in the main experiment. Measurements included lamb birth weight and survival and, in the main experiment only, ewe milk production and lamb immunoglobulin concentrations. With 9 days of lupin grain supplementation, lamb survival to weaning increased by about 12% (P<0.05), size of litter weaned increased from 1.26 to 1.52 (P<0.01) and lamb birth weight increased by about 0.2 kg (P<0.01). In the main experiment, supplementation with lupins resulted in 95% survival to day 9 of twin-born lambs, compared with 68% for lambs from control and oat-fed ewes (P<0.05). Extra lamb losses, due to starvation in the unsupplemented group, were matched by losses due to dystocia in the fed groups. Lamb birth weights, and ewe milk production and composition, were similar across treatments. During the feeding treatment period, only the lupin supplemented ewes maintained their fat score while the other ewes lost 0.5 of a fat score (P<0.01). Fewer (P<0.1) multiple-born lambs from lupin supplemented ewes had low serum immunoglobulin scores, indicating that the lupin supplement may have affected production or intake of colostrum.
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Haslin, Emmanuelle, Rene A. Corner-Thomas, Paul R. Kenyon, Emma J. Pettigrew, Rebecca E. Hickson, Steve T. Morris y Hugh T. Blair. "Effect of Breeding Heavier Romney Ewe Lambs at Seven Months of Age on Lamb Production and Efficiency over Their First Three Breeding Seasons". Animals 11, n.º 12 (7 de diciembre de 2021): 3486. http://dx.doi.org/10.3390/ani11123486.
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This experiment examined the effect of breeding heavier ewe lambs on lamb production and their efficiency over their first three breeding seasons. Two groups of ewe lambs were bred at seven months of age at an average pre-breeding live weight of either 47.9 ± 0.36 kg (heavy; n = 135) or 44.9 ± 0.49 kg (control; n = 135). Ewe live weight, number of lambs born and weaned, and lamb live weight were recorded until 39 months of age, and efficiency was calculated for each ewe. Although the number and lamb weaning weight did not differ between treatments over three years, when data were pooled, heavier ewe lambs at breeding weaned a greater number of lambs over the three-year period. The total lamb weaning weight over the three-year period increased by 2% for each additional kilogram at ewe lamb breeding. Breeding heavier ewe lambs had no effect on efficiency. These results suggest that although breeding heavier ewe lambs had a positive effect on lamb production over the three-year period, it had no effect on efficiency. Before final recommendations can be made, lifetime performance and longevity to five years of age of heavier ewe lambs at breeding are required.
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Fogarty, N. M. y J. G. Mulholland. "Growth and carcass characteristics of crossbred lambs in various production systems". Animal Production Science 52, n.º 5 (2012): 373. http://dx.doi.org/10.1071/an11336.
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Lamb growth, carcass and pelt measurements are reported from 5775 lambs born to Border Leicester × Merino (BLM) and Hyfer (Dorset × Merino composite) ewes joined to Dorset, Suffolk and Hyfer rams in three lamb-production systems at Cowra and Wagga Wagga over 5 years. The production systems involved lambings at different seasons of the year and increasing levels of intensification from autumn annual joining, spring joining with a backup mating for non-pregnant ewes, to an accelerated 8-monthly lambing system. Lambs from BLM ewes were 0.7 kg heavier at birth and grew 3% faster and reached slaughter, at 18 kg carcass weight, 1–2 weeks earlier than did lambs from Hyfer ewes (P < 0.01). The advantage in growth rate of lambs from BLM compared with Hyfer ewes was greater for lambs born in November. These lambs had poorer growing conditions over the summer months, with 22% lower growth rate and taking 5 weeks longer to reach slaughter than did lambs born in March or August. There was no difference between Dorset and Suffolk sire breeds for any lamb growth traits, with lambs from Hyfer sires growing 7% slower. Ram and cryptorchid lambs reached slaughter 1 week earlier than did wethers, with ewes a further 9 days later (P < 0.01). Sex differences were maximised when lamb growth was greatest. There were no differences in carcass fat measurements between ram and cryptorchid lambs, although both were considerably leaner than wethers (2.2–3.0 mm fat at the GR site), which were 1.3–2.1 mm leaner than ewes at 18-kg carcass weight. The range in average growth rate of progeny of the BLM ewes from the 12 different source flocks at Cowra and Wagga Wagga was 10–14% of the mean which was twice the difference in average growth rate of progeny from the BLM and Hyfer dams. There was also significant variation among the BLM source flocks for carcass fat measurements. Lamb progeny from the different sire- and dam-breed combinations had varying levels of heterozygosity. There appears to be little loss of heterosis or hybrid vigour for lamb growth, although the sire breed × dam breed interaction was significant (P < 0.01) for age at slaughter at Wagga Wagga, in which the ranking of the lamb types was consistent with the levels of heterozygosity. The estimates of between-lambing repeatability for the ewes were highest for birthweight (0.35 Cowra and 0.27 Wagga Wagga) and declined at later ages (0.26–0.17), with lower estimates for carcass traits.
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Keogh, T. P., S. R. McGrath, V. H. Oddy, M. Hernandez-Jover, H. Dickson y M. B. Allworth. "Are there opportunities to improve lamb feedlot production efficiency? A cross-sectional survey". Animal Production Science 62, n.º 4 (14 de diciembre de 2021): 381–91. http://dx.doi.org/10.1071/an21309.
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Context Feedlotting lambs has the potential to considerably increase the efficiency of lamb production in Australia. Many producers have turned to grain-finishing lambs to capitalise on high lamb prices and, due to the perceived profitability of this practice, further research to improve production has not been prioritised. Lambs are, however, difficult to adapt to a predominantly grain-based diet, often resulting in highly variable feed intake and growth rates. Aims The aim of this survey was to investigate the apparent growth rates and feed conversion ratios of lambs in current feedlotting enterprises. A secondary aim was to identify research priorities that could improve feedlot production efficiency. Methods A cross-sectional survey was conducted between February and May 2020 among Australian lamb producers, with the target population being lamb producers using feedlots to finish lambs. Producer responses from 59 current lamb feedlotters were collated and analysed. Key results The most frequently reported growth rates were between 300 and 350 g/day, and most respondents reported a feed conversion ratio of 5:1. The incidence of shy feeders was a median of 3.5% and mortality was a median of 1%, with acidosis reported as the major contributor to mortality. Conclusions The results of the current survey indicate that for the majority of responding producers, lamb growth rates and feed conversion ratios are consistent with those predicted by the nutrient requirements of domesticated ruminants (CSIRO 2007), and improvements in production are unlikely without significantly increasing nutrient intake. Shy feeders, acidosis and the intake of lowly digestible feeds are the clear limitations to production efficiency. Implications Research to improve productivity of lambs in feedlots needs to prioritise the implementation of feeding strategies that minimise social and nutritional issues, and promote maximum intake of nutrients.
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Xiao-Yong, Chen, Tian Shu-Jun, Sang Run-Zi, Sun Shu-Chun, Zhao Zhu-Jun, Li Jun-Jie y Dun Wei-Tao. "Induction of lamb follicular development and embryo production in vitro". Chinese Journal of Agricultural Biotechnology 5, n.º 3 (diciembre de 2008): 257–62. http://dx.doi.org/10.1017/s1479236208002428.
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AbstractEffect of lamb age, transport stimulation and repeated hormone superovulation on the number of collected oocytes were determined. Effect of the culture medium containing ethylenediaminetetraacetic acid (EDTA) on the development of embryos produced in vitro from lamb oocytes was also investigated. Results indicated that the mean numbers of collected and available oocytes (oocytes with compacted cumulus cells, evenly granulated ooplasm and morphologically normal) from 6- to 8-week-old lambs were 60.8±13.9 and 58.2±12.3, respectively. These figures were higher than those obtained from 12- to 14-week-old lambs (27.3±5.1 and 26.0±4.9) (P<0.05). Stimulation by transportation didn't decrease the number of collected oocytes from the superovulated lambs (P>0.05). However, the number of collected oocytes in the repeated superovulation group was significantly reduced, compared with the control group (P<0.05). The embryonic culture medium supplemented with 10 μmol/l EDTA highly improved the development capability of the embryos from lamb oocytes (P<0.05). Healthy lambs were born following embryo transfer.
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El Fadili, M., C. Michaux, J. Detilleux y P. L. Leroy. "Comparison of five crossbreeding types involving Timahdit, D’man and improved terminal sire breeds of sheep: ewe reproduction, lamb survival and growth performance". Animal Science 71, n.º 3 (diciembre de 2000): 435–41. http://dx.doi.org/10.1017/s1357729800055351.
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AbstractA crossbreeding experiment involving Timahdit (T), D'man (D) and improved sire breeds (M) was conducted to compare lamb production in five crossbreeding types: D ✕ D, T ✕ T, D ✕ T (DT), M ✕ T, and M ✕ DT lambs. Reproductive and production traits were analysed in 1187 litters, 1586 lambs born and 1346 lambs weaned, progeny of 605 ewes. Effects of crossbreeding type, year of birth, sex of lamb, age of dam, and type of birth were significant on the majority of traits studied. The D ✕ D and M ✕ DT crossbreeding system showed the highest litter sizes at lambing and at weaning with respective values in D ✕ D (2·17, 1·34) and M ✕ DT (1·72, 1·39). Ewes bearing the M ✕ DT cross lambs showed the highest (P < 0·05) litter weight at weaning (28·28 kg) followed by those with M ✕ T (23·14 kg), and D ✕ D (22·53 kg) lambs. M ✕ DT and M ✕ T lambs were heavier and grew faster than the other lambs. On the other hand, lamb survival rates and growth traits were the lowest in D ✕ D but those in T ✕ T and D ✕ T genetic types of lamb were intermediate. Results showed that D as a dam breed had a favourable effect on litter size (P < 0·01) but unfavourable effect on lamb survival and birth weight. The reproductive performance of DT crossbred ewes, due to their high prolificacy and lamb survival, associated with the favourable effect of an improved terminal sire (M) for growth traits, indicated that the three breed cross (M ✕ DT) could enhance lamb production in Morocco.
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Morgan, J. E., N. M. Fogarty, S. Nielsen y A. R. Gilmour. "The relationship of lamb growth from birth to weaning and the milk production of their primiparous crossbred dams". Australian Journal of Experimental Agriculture 47, n.º 8 (2007): 899. http://dx.doi.org/10.1071/ea06290.
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The growth rate of 667 single cross lambs from birth to 4 weeks (Period 1) and 4 weeks to weaning at 12 weeks (Period 2) was measured, along with the milk production of their 520 primiparous crossbred ewe dams over 3 years. The lambs were the progeny of Poll Dorset rams and first cross ewes lambing for the first time at 12 and 19 months of age. The first cross ewes were the progeny of Merino ewes mated to 30 individual sires from several maternal sire breeds, including Border Leicester, East Friesian, Finnsheep and Coopworth. Milk production of the ewes was measured at ~3, 4 and 12 weeks of lactation using a 4-h milk test. The effect of ewe milk production on lamb growth rate in Period 1 included a significant interaction with lamb birth and rearing type (P < 0.001). These regressions were 52 ± 18 g/day per kg/day for single born and reared, 24 ± 17 g/day per kg/day for multiple born and single reared and 18 ± 17 g/day per kg/day multiple born and reared lambs. The regression of ewe milk production in Period 2 on lamb growth rate in Period 2 was also significant (P < 0.001), although milk production in Period 1 accounted for more variation in lamb growth. There were significant interactions of ewe weight gain (from mid pregnancy to lamb weaning) with season in Period 1 (P < 0.01) and year in Period 2 (P < 0.001). There was also a significant interaction (P < 0.001) of year with ewe mid-pregnancy weight for lamb growth in Period 2. Lamb birthweight had a significant effect on lamb growth rate in Period 2 (regression coefficient 6.68 ± 2.57 g/day.kg, P < 0.01).
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Raineri, C., T. S. S. Stivari y A. H. Gameiro. "Lamb Production Costs: Analyses of Composition and Elasticities Analysis of Lamb Production Costs". Asian-Australasian Journal of Animal Sciences 28, n.º 8 (5 de febrero de 2015): 1209–15. http://dx.doi.org/10.5713/ajas.14.0585.
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Fogarty, N. M., V. M. Ingham, L. McLeod, G. M. Gaunt y L. J. Cummins. "Genetic resources to increase the profitability of crossbred lamb production". Australian Journal of Experimental Agriculture 46, n.º 7 (2006): 799. http://dx.doi.org/10.1071/ea05355.
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The gross margin returns of first cross ewes by different sires have been evaluated on an equivalent carrying capacity basis by taking account of the feed requirements for the ewes and lambs and their varying performance and requirements throughout the annual production cycle. The study involved 2846 crossbred ewe progeny generated by 91 maternal sires from several breeds at 3 sites over 3 years including genetic links. The ewes were joined to terminal sire rams for 3 years and 8878 of their second cross lamb carcasses were included in the evaluation. The annual gross margin (A$GM) for individual ewes included income from lamb carcasses (with fat and weight discounts), lamb skins and ewe wool production, and costs for management and marketing. Individual feed requirements were calculated for ewe maintenance, gestation, lactation and lamb growth (pre- and post-weaning) and $GM was expressed on a dry sheep equivalent (dse) basis. Sire breed was not significant with a range of $5.28 GM/dse between sire breed means. There was a considerably greater range of up to $15 GM/dse among most of the sire ewe progeny groups within breeds and overlap among all sire breeds. Lamb turnoff rate was the major profit driver with lamb growth rate and carcass fat levels also contributing. The opportunities for genetic improvement in profitability of lamb enterprises are discussed.
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Fogarty, N. M., D. L. Hopkins y R. van de Ven. "Lamb production from diverse genotypes. 1. Lamb growth and survival and ewe performance". Animal Science 70, n.º 1 (febrero de 2000): 135–45. http://dx.doi.org/10.1017/s1357729800051675.
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AbstractGrowth and survival of 3673 female and cryptorchid lambs representing the range of types (second cross, first cross and Merino) produced in the Australian lamb industry are reported. The lambs were sired by a selection of Poll Dorset (D; no. = 7), Texel (T; no. = 10), Border Leicester (BL; no. = 12) and Merino (M; no. = 12) rams and born to Border Leicester × Merino (BLM) and Merino (M) dams, which resulted in six lamb genotypes (D×BLM, T×BLM, D×M, T×M, BL×M and M×M). The second cross lambs (D×BLM, T×BLM) were heavier at birth, weaning and post-weaning and had higher growth rates, than first cross lambs (D×M, T×M, BL×M), which were higher than M×M lambs (P< 0·01). For post-weaning weight (cryptorchids at 156 days) second cross lambs were 4·2 (s.e. 0·3) kg heavier than comparable sired first cross lambs, with the BL×M 2·6 (s.e. 0·5) kg lighter than other first cross types and the MxM a further 4·2 (s.e. 0·6) kg lighter. The average advantage of D over T crosses was 1·0 kg for post-weaning weight, with greater variation amongst individual sires.Lamb survival to weaning was 76% and it was affected by birth weight and birth type (P< 0·01). Sire breed had no significant effect on lamb survival, whereas lambs from BLM ewes had higher survival than those from M ewes (P< 0·01).Overall the proportion of ewes lambing was 84% with a mean litter size of 1·77. There was no difference infertility between AI (thawed frozen semen and laparoscopic insemination) and natural (single sire) mating, although the M were higher than the BLM ewes (P< 0·01). Gestation length was 2·3 days shorter (P< 0·01) for BLM than M ewes and there was no difference between D and T sire breeds. There was little effect of birth type on gestation length but it increased with birth weight within birth type categories. Between year repeatability of gestation length for ewes was 0·33 (s.e. 0·05).
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Fogarty, N. M. y J. G. Mulholland. "Annual lambing performance of crossbred ewes in out-of-season and accelerated lamb production systems". Animal Production Science 53, n.º 10 (2013): 1093. http://dx.doi.org/10.1071/an12269.
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The average annual lamb production of 1182 crossbred ewes was evaluated in three lamb production systems over 4 years at two sites (Cowra and Wagga Wagga). The lamb production systems were: accelerated 8-monthly joinings with two flocks joined 4 months apart (Ac8), spring joining with an autumn back-up joining (SpB), and annual autumn joining (AuA). The Ac8 and SpB systems were evaluated at Cowra and the SpB and AuA systems were evaluated at Wagga Wagga. Two genotypes of ewes, Border Leicester × Merino (BLM) and Hyfer (Dorset × Merino composite), were used at both sites, with natural joinings to Dorset, Suffolk or Hyfer rams. Four traits were analysed separately at each site to evaluate the average performance per ewe joined per year: number of lambings, number of lambs born, number of lambs weaned and total weight of lamb weaned. Analyses were also undertaken using only spring joining data. At Cowra ewes in the Ac8 system had more lambings (1.23 vs 0.87), lambs born (1.88 vs 1.28), lambs weaned (1.47 vs 1.00) and weight of lamb weaned (31.1 vs 21.5 kg) than ewes in the SpB system (P < 0.01). At Wagga Wagga the AuA system had significantly more lambs born (1.37 vs 1.13), lambs weaned (1.08 vs 0.95) and weight weaned (26.1 vs 21.9 kg) than the SpB system (P < 0.01). The system × breed interaction was significant for all traits because the BLM ewes were greater than Hyfer ewes in the AuA, but the reverse in the SpB system. At both sites the advantage of the back-up joining over only joining in spring was greater for the BLM than the Hyfer ewes. The relative performance of the various lamb production systems for each ewe breed is presented. An accelerated lambing system is likely to be more successful using ewes that have an extended breeding season and good out-of-season breeding performance.
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Lambe, N. R., J. Conington, K. A. McLean, L. Bunger y G. Simm. "Relationships between mobilisation of body reserves in hill ewes and lamb production to weaning". Proceedings of the British Society of Animal Science 2007 (abril de 2007): 118. http://dx.doi.org/10.1017/s1752756200020214.
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Previous studies using X-ray computed tomography (CT) of Scottish Blackface hill ewes have shown that carcass fat, internal fat and muscle are depleted during pregnancy and early lactation and deposited during late lactation and the dry period (Lambe et al., 2003a). Muscle weights and proportions throughout the year are positively genetically correlated with total litter weight reared, largely due to increased litter size. Average weights of lambs reared were positively correlated with carcass fat weight or proportion pre-lambing and internal fat weight pre-mating, but negatively correlated with internal fat proportion pre-lambing (Lambe et al., 2005). However, is genetic potential to mobilise and regain increased amounts of tissue during the year positively associated with the ability to produce more and heavier lambs? The aim of this study was to address this question by relating total loss and gain of fat and muscle in ewes during the annual cycle with lamb production traits.
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Fogarty, NM, LD Brash y AR Gilmour. "Genetic parameters for reproduction and lamb production and their components and liveweight, fat depth and wool production in Hyfer sheep". Australian Journal of Agricultural Research 45, n.º 2 (1994): 443. http://dx.doi.org/10.1071/ar9940443.
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Hyfer is a new composite breed suited to specialized lamb production and developed from Dorset (+), Booroola Merino (+)and Trangie Fertility Merino (+) genotypes. Genetic parameters estimated by restricted maximum likelihood methods are reported for liveweight, wool production and a range of reproduction and lamb production traits. Estimates of heritability were 0 44 � 0.10, 0.222 � 0-08 and 0.28 � 0.08 for liveweight, ultrasonic fat depth (C site) and fat depth adjusted for liveweight respectively, for 1454 rams averaging 14 months of age, which were the progeny of 130 sires. The genetic correlation for ram liveweight and fat depth was 0.06 � 0.17 and -0.30 � 0.16 with adjusted fat depth. Estimates of heritability for ewe liveweight at 12-18 months of age and greasy fleece weight at 11-19 months of age were 0.61 � 0.10 and 0.38 � 0.08 respectively, with a genetic correlation of 0.35 � 0.13, based on 1619 ewes, which were the progeny of 135 sires. A maternal effect was significant for ewe liveweight and its inclusion in the model reduced the estimate of heritability to 0.44 � 0.09. Young ewes were joined three times in two years in an accelerated 8-monthly lambing system, and joinings commenced in mid-February, late October and mid-June. The estimates of heritability for overall ewe performance were for lambs born 0.09 � 0.03, lambs weaned 0.04 � 0.02 and weight of lamb weaned 0 -06 � 0.02 (all per ewe joined). Heritabilities for the component traits were: fertility 0 -03 � 0 02, litter size 0.19 � 0.04 and lamb survival 0.07 � 0.03. Estimates of repeatability for the corresponding traits ranged from 0.11 to 0.15, except for litter size (0.26 � 0.02). Estimates of heritability for lambs born, lambs weaned and weight weaned were higher for the first joining than when estimates were based on three joining records. This was associated with higher heritability for fertility from first joining (0.10 � 0.06) than for all three records and the reverse for lamb survival. Estimates of heritability for mean ewe performance were considerably higher and in agreement with the values predicted from the repeatability analyses and number of records, illustrating the value of using repeated ewe records for selection. The genetic correlations between the component traits and overall measures of lamb production were not high enough to consider using component traits as indirect selection criteria. The genetic correlations of liveweight with reproduction traits were positive, but generally not significant, and ranged from 0.01 to 0.63, except for litter size (-0.19 � 0.17). The genetic correlations of greasy fleece weight with reproduction traits were generally smaller than those for liveweight, were not significant and ranged from -0.12 to 0.32. These results, together with others, will be used to compile parameter sets for use in LAMBPLAN to provide meatsheep breeders with comprehensive breeding objectives incorporating growth, leanness, wool and reproduciton.
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Busboom, J. R., T. I. Wahl y G. D. Snowder. "Economics of callipyge lamb production". Journal of Animal Science 77, suppl_2 (1999): 243. http://dx.doi.org/10.2527/1999.77suppl_2243x.
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KERSLAKE, J. I., P. R. KENYON, K. J. STAFFORD, S. T. MORRIS y P. C. H. MOREL. "Can maternal iodine supplementation improve twin- and triplet-born lamb plasma thyroid hormone concentrations and thermoregulation capabilities in the first 24–36 h of life?" Journal of Agricultural Science 148, n.º 4 (20 de mayo de 2010): 453–63. http://dx.doi.org/10.1017/s0021859610000286.
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SUMMARYThe present study investigated the effects of maternal plasma iodine concentration on twin- and triplet-born lamb plasma thyroid hormone concentrations, rectal temperature and maximal heat production. On pregnancy day 68 (P68), 16 twin- and 14 triplet-bearing ewes were randomly chosen from ewes that were injected intramuscularly with 1·5 ml of iodized peanut oil and ewes that were not. Selected ewes were grazed on ad libitum pasture from P68 until parturition. After parturition, lamb blood samples were collected within 5 min of birth and at 3, 12 and 24–36 h after birth. Lamb rectal temperatures were measured within 5 min of birth and at 1, 3 and 12 h after birth. Lamb body weight, crown–rump length and thoracic-girth circumference were recorded at 3 h of age, and the capability of the lamb to produce heat at 24–36 h of age was measured using indirect open-circuit calorimetry. Maternal iodine supplementation successfully increased plasma iodine concentrations of twin- and triplet-bearing ewes throughout pregnancy, but had no effect on the rectal temperature, thyroid hormone concentration and maximal heat production of twin- or triplet-born lambs. Compared with twin-born lambs, triplet-born lambs had lower birth weights, rectal temperatures and plasma T4 and T3 concentrations within 5 min of birth. Overall, under the conditions of the present study, maternal iodine supplementation offered no benefit in improving lamb heat production.
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Gootwine, E., A. Bor, R. Braw-Tal y A. Zenou. "Reproductive performance and milk production of the improved Awassi breed as compared with its crosses with the Booroola Merino". Animal Science 60, n.º 1 (febrero de 1995): 109–15. http://dx.doi.org/10.1017/s1357729800008201.
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AbstractOvulation rate, embryo survival, lamb production, lamb survival and milk production of Awassi and BooroolaAwassi crossbred ewes, kept indoors, were compared. Awassi were non-carriers while Booroola × Awassi (F1) and about half of 3/4 Awassi-1/4 Booroola (BQ) ewes were heterozygous at the FecB gene. Mean ovulation rate increased by 1·5 to 1·6 corpora lutea per ewe ovulating and prolificacy by 0·7 lambs born per ewe lambing in Fj and BC1 (B+) ewes as compared with Awassi. Embryo survival rates in BC1 ewes with two, three and four ovulations were 0·83, 0·68 and 0·71, respectively. Lamb survival rates at 1 day of age were 0·93, 0·90 and 0·77 and average birth weight was 4·9, 4·0 and 3·0 kg for lambs born as singles, twins and triplets, respectively. Average milk production of the Awassi was 506 I per ewe per lactation. F1 and BC1 ewes produced respectively, proportionately 0·48 and 0·63 of the Awassi milk production and there was no significant difference in milk production between BC1,(B+) and BC1(++) ewes. The relatively low milk production of the Booroola Awassi crosses suggests that heterosis and recombination effects on milk production were negative. It is concluded that incorporation of the B allele per se can increase lamb production in the Awassi without affecting its milk production.
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Wuliji, Tumen, Amy Bax, Liga Wuri, Luke Wilbers y Christopher Boeckmann. "167 Evaluation of an out-of-season breeding system for organic lamb production in missouri". Journal of Animal Science 97, Supplement_3 (diciembre de 2019): 173–74. http://dx.doi.org/10.1093/jas/skz258.357.
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Abstract Organic production is one of the fastest growing food and agriculture industry. The seasonality of lamb production affects lamb markets and prices, whereas, an out-of-season breeding and organic fall lamb production scheme may enhance product availability and competiveness. Six rams and 100 Katahdin ewes were selected for an out-of-season breeding during April and May of 2017 and 2018, for two production years. Ewes were synchronized for estrus using CIDR® device (EaziBreed™) (12 d) before breeding and fed ‘flushing’ feed for four weeks. Ewes were bred in mixed sire groups for two estrus cycles (35 d). Animals were rotationally grazed and maintained good body condition score (3.0) throughout the seasons at certified organic farm in Missouri. Mean live weight measured monthly from breeding to lambing were 57.8, 60.1, 62.1, 64.7, and 59.3 kg. Eighty nine ewes lambed in fall 2017 giving birth to 121 lambs (136% lambing rate) and eighty eight ewes lambed in 2018 giving birth to 126 lambs (143% lambing rate). Ninety seven percent of weaned lambs were maintained as an organic production status for marketing. Lamb birth weight, average daily gain weight, weaning weight, and 30 d post weaning weight, post weaning average daily gain weight were recorded for 2017 born lambs as 3.74±0.03 kg, 21.00±0.24 kg, 24.78±0.28 kg, 176±2 g/d respectively. Organic weaner lambs were sold for 5 to 15% higher price values (P < 0.05) per unit than non-organic peer groups at a local livestock auction sale.
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Holst, P. J., D. F. Stanley, G. D. Millar, A. Radburn, D. L. Michalk, P. M. Dowling, R. Van de Ven et al. "Sustainable grazing systems for the Central Tablelands of New South Wales. 3. Animal production response to pasture type and management". Australian Journal of Experimental Agriculture 46, n.º 4 (2006): 471. http://dx.doi.org/10.1071/ea04041.
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The main limitations for prime lamb production in the Central Tablelands of New South Wales are low availability of forage early in the growing season (late autumn–early winter) and low nutritive value in the summer. This paper describes the performance of a first-cross lamb breeding enterprise on 4 pasture types and 2 management systems over 4 years for the Central Tablelands region. The pastures studied comprised a traditional unfertilised naturalised pasture, a similar pasture fertilised with superphosphate, a sod-sown fertilised introduced perennial grass pasture and a sod-sown summer growing perennial, chicory (Cichorium intybus L.) pasture. Grazing management involved either continuous grazing or tactical grazing that combined a lower annual stocking rate with an optional summer rest to maintain perennial grass content above 50%. An additional area of chicory pasture was set aside for finishing lambs. Over the experiment stocking rates were increased each year as the pasture became established, with increases ranging from 1.5 ewes/ha for tactically grazed unfertilised natural pasture to 3.6 ewes/ha, for chicory and clover pasture. The feed quality v. quantity problem of summer and autumn was reaffirmed for each pasture type except chicory and the lamb enterprise appeared to be sufficiently adaptable to be promising. Ewes lambed in September and produced satisfactory lamb growth rates (about 280 g/day for twins) on the various pastures until weaning in late December. Thereafter, lamb growth rates declined as the pastures senesced, except chicory, reaffirming the feed quality v. quantity problem in summer and autumn of naturalised and sown grass pastures for producing lamb to heavyweight market specifications. Weaning liveweights (in the range of 32–40 kg) from grass-based pastures were high enough for only about 45% of the lambs to be sold as domestic trade lambs with the remainder as unfinished lambs. In contrast, the chicory and clover finishing pasture produced lamb growth rates of 125 g/day and quality large, lean lambs suitable for the export market. Vegetable matter in the late January shorn wool was insignificant and there was no significant effect of pasture on fleece weight, fibre diameter or staple strength. Position of break in staples of wool from chicory pastures differed from that of the other pasture types and warrants further study on time of shearing. It was concluded that a first cross lamb producing enterprise of suitable genetics was effective in producing trade and store lambs before pasture senescence, but the inclusion of a specialised pasture of summer growing chicory would create greater opportunities. In the unreliable summer rainfall region of the Central Tablelands, the area of chicory pasture needed to maintain lamb growth rates of >125 g/day, estimated from these results, is around 10 lamb/ha of chicory.
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Campbell, Braden J., Jefferson S. McCutcheon, Francis L. Fluharty y Anthony J. Parker. "PSIII-5 Delaying Weaning Age of Lambs Grazing Chicory (Cichorium Intybus) Increases Body Weight". Journal of Animal Science 99, Supplement_1 (1 de mayo de 2021): 157. http://dx.doi.org/10.1093/jas/skab054.269.
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Abstract Two common challenges in forage-based lamb production systems is the restriction of net energy from grass-based pastures and the production losses associated with parasitic infection. The inclusion of nutrient rich forage in the diet and delaying lamb weaning age has shown to improve lamb growth rates in some systems. The objective of this experiment was to investigate the effects of grazing chicory (Cichorium intybus) and delayed weaning on the growth and health of young pasture-raised lambs. We hypothesized that improving the quality of available forage and delaying weaning would increase the body weight and parasite resilience of lambs. A total of 18 cross-bred ewes and 36 cross-bred lambs (25.2 ± 0.5 kg) were stratified by weight, sex, and randomly assigned to one of two weaning treatments: lambs weaned at 60 days of age (weaned) and lambs remained with their dam and weaned at 120 days of age (delayed weaned). Data were analyzed using PROC MIXED in SAS. Lamb body weight and indices of parasitism were measured every 14 days. There was a treatment × day effect for body weight as delayed weaned lambs were heavier on days 28, 42, and 56 compared with the body weight of weaned lambs (P < 0.02). In addition, there was a treatment × day effect for average daily gain (ADG) whereas delayed weaned lambs demonstrated greater ADG on days 14, 28, 42, and 56 compared with the ADG of weaned lambs (P < 0.02). In monitoring lamb health, there was a treatment × day effect as weaned lambs had a greater packed cell volume (PCV) on day 14 compared with the PCV of delayed weaned lambs (P < 0.03). Conversely, on day 56, weaned lambs had a lower PCV compared with the PCV of delayed wean lambs (P < 0.004). Delayed weaning has shown to be beneficial in improving lamb growth; however, in this instance, delayed weaning demonstrated variable responses in supporting lamb health while grazing on improved pastures.
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Pettigrew, Emma, Rebecca Hickson, Steve Morris, Paul Kenyon, Rene Corner-Thomas, Emmanuelle Haslin y Hugh Blair. "The Effect of Age of Dam and Birth Rank on the Reproductive Performance of Ewes as One- and Two-Year-Olds". Animals 11, n.º 3 (10 de marzo de 2021): 770. http://dx.doi.org/10.3390/ani11030770.
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Currently, 30–43% of New Zealand sheep farmers breed their ewe lambs, but few retain the offspring as replacements for their flock. No difference in lamb production as a yearling among singletons and twins born to ewe lambs and twins born to mature ewes has been reported, provided the ewe lambs had reached the 60–65% of their likely mature weight prior to breeding at seven to eight months of age. The aim of this experiment was to determine the lamb production from singletons and twins born to ewe lambs and twins born to mature ewes during their first two years of lambing. The experiment included 8-month-old ewes born as twins to mature ewes (M2, n = 135), singletons born to ewe lambs (L1, n = 135), and twins born to ewe lambs (L2, n = 88), bred during the same period to the same rams, over two years. The efficiency of lamb production (total litter weight at weaning divided by the pre-breeding weight of the ewe, for all ewes presented for breeding) after two years of production was not significantly different (p > 0.05) among the groups (0.40 ± 0.02, 0.39 ± 0.02, and 0.39 ± 0.03, for M2, L1, and L2, respectively).
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Speijers, M. H. M., L. E. R. Dawson, A. F. Carson, D. J. Kilpatrick y B. W. Moss. "The effect of genotype and diet on lamb meat quality from hill sheep systems". Proceedings of the British Society of Animal Science 2009 (abril de 2009): 47. http://dx.doi.org/10.1017/s1752756200028866.
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Crossbreeding can be used in the hill sector to improve the efficiency of production. Carsonet al. (2001) showed that ram breed substitution increased lamb output per ewe by 24% with concomitant improvements in carcass quality. However, information is required for a range of crossing sire breeds for the hill sector to enable the most effective crossbreeding programmes to be developed. Therefore, the primary aim of this study was to evaluate the effects of a range of lamb genotypes on lamb meat quality. Furthermore, a range of production systems (long-keep grass-based systems to short-keep concentrate-based systems) are used to finish hill lambs. Diet type (i.e. roughage-versus concentrate-based) can also affect lamb growth rates and carcass characteristics (Carsonet al., 2001). Consequently, a secondary aim of this study was to evaluate the effects of diet and its interaction with lamb genotype on lamb meat quality.
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Hass, Christine C. "Bighorn lamb mortality: predation, inbreeding, and population effects". Canadian Journal of Zoology 67, n.º 3 (1 de marzo de 1989): 699–705. http://dx.doi.org/10.1139/z89-101.
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Survival of lambs in the population of bighorn sheep (Ovis canadensis) on the National Bison Range, Montana, was less than 25% during 1983 and 1984. Sixty-seven percent of lamb mortality occurred within 3 days of birth; ewe behaviour and recovered remains indicated that coyotes likely accounted for most of the mortality. Herd history, calculated inbreeding coefficients, and the observation of several small, weak lambs implied that inbreeding depression, while probably not a major factor in lamb mortality, may have predisposed some lambs to predation. Lamb production was high (88–96%); in spite of high mortality, population numbers were stable.
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Fogarty, NM y DG Hall. "Performance of crossbred progeny of Trangie Fertility Merino and Booroola Merino rams and Poll Dorset ewes. 3. Reproduction, liveweight and wool production of adult ewes". Australian Journal of Experimental Agriculture 35, n.º 8 (1995): 1083. http://dx.doi.org/10.1071/ea9951083.
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Reproduction, liveweight and wool production are reported for 4 cohorts of 377 Trangie Fertility x Dorset (TD) and 261 Booroola x Dorset (BD) ewes over 6 years. The BD ewes were 3-4 kg lighter (P<0.001) and had a higher ovulation rate prior to joining in February-March (2.37 � 0.03 v. 1.65 � 0.03) than TD ewes. This resulted in a higher litter size (2.07 � 0.03 v. 1.66 � 0.04) and number of lambs born per ewe joined (1.92 � 0.04 v. 1.56 � 0.04) for the BD ewes. Lamb survival was lower from BD than TD ewes (0.71 � 0.02 v. 0.85 � 0.02), so that the 2 ewe strains weaned the same number of lambs. The growth rate of lambs was lower from the BD ewes and overall they weaned 3.8 kg less (P<0.001) weight of lamb than TD ewes. Chill (index of environmental conditions at lambing), litter size and average birth weight of lambs in the litter (linear and quadratic) affected (P<0.001) lamb survival. At moderate levels of chill there was little difference in survival of single and twin lambs from BD and TD dams when birth weight was 4-5 kg, but survival declined more rapidly for progeny of BD ewes at lower birth weight. Under severe lambing conditions survival was depressed more for lambs born from BD ewes than TD ewes. Almost all ewes expressed oestrus over the 3, 6-week periods, December-January, January-February and March (joining). There was significant variation (P<0.001) in incidence of oestrus due to year and age (linear and non-linear), but not liveweight at joining, and there was little difference between ewe strains. Similarly, for post-lambing oestrus (to fit 8-monthly joining) and post-lambing anoestrous interval, there was little difference between strains, but year and age were highly significant (P<0.001). BD ewes had a lower (P<0.001) greasy fleece weight (3.76 v. 3.86 kg), than TD ewes. BD ewes were classified as either carriers (F+) or non-carriers (++) of the FecB gene, which was significant (P<0.001) for ovulation rate (+1.14 ovulations), litter size (+0.8 lambs), lamb survival (-18%), lambs born per ewe joined (+0.64 lambs) and total weight of lamb born per ewe joined (0.5 kg, P<0.01). The effect of the FecB gene was non-significant for lamb survival when litter size and lamb birth weight (P<0.001) were included in the model. Repeatability estimates based on over 3 records per ewe were about 0.2 for lambs born, weight of lamb born, lambs weaned and weight of lamb weaned per ewe joined. Component traits ranged from 0.27 for litter size to 0.10 for lamb survival, with fertility intermediate (0.15). Greasy fleece weight (0.72) and ovulation rate (0.41) had high repeatabilities with post-lambing anoestrous interval being low (0.11). Repeatability for ovulation rate was reduced to 0.34 when F+ ewes were excluded.
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Fleet, M. R., M. J. Bennie, G. N. Dunsford, G. R. Cook y D. H. Smith. "Lamb production from Merino ewes mated to Merino or Damara rams". Australian Journal of Experimental Agriculture 42, n.º 8 (2002): 1027. http://dx.doi.org/10.1071/ea01073.
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Damara sheep have recently been imported to Australia and are being crossed with Merino ewes as a diversification from wool to fat tail sheep production for live sheep export or meat markets. A comparison was made of the lamb outputs from Merino ewes mated to 2 Merino rams and 2 Damara fat tail rams. There were more multiple litters produced in the matings with the Damara rams than from the Merino rams (P = 0.01). The 5-month weights of the crossbred lamb groups (36.3 and 38.9 kg) were higher (P<0.05) than the Merino groups (33.4 and 32.3 kg). Ram lambs were slaughtered at 7 months of age and the carcasses dissected into 'trim lamb' lean portions, fat trims, bone and other oddments. Dressing percentage at slaughter of the crossbred lambs was 3–4% higher (P<0.001), reflecting lower wool production, than the Merino lambs. After adjustment for chilled carcass weight, there were no differences (P>0.05) between rams for the total amount of lean meat. However, the crossbred groups had more external carcass fat (2.59 and 2.64 kg) than the Merino groups (2.14 and 2.15 kg) and, in addition, had fat tail weights of 0.52 and 0.36 kg.
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Badgery, W. B., G. D. Millar, D. L. Michalk, P. Cranney y K. Broadfoot. "The intensity of grazing management influences lamb production from native grassland". Animal Production Science 57, n.º 9 (2017): 1837. http://dx.doi.org/10.1071/an15866.
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The intensity of grazing management required for optimal pasture and animal production from heterogeneous native grasslands has received little research in the high-rainfall zone of south-eastern Australia. The aim of this experiment was to determine how the intensity of grazing management, from continuous grazing (P01) to flexible 4- and 20-paddock rotational systems (P04 and P20), influenced the productivity and sustainability of a Merino ewe, terminal sire lamb production system run on a native grassland dominated by Microlaena stipoides and Rytidosperma spp. The present paper focuses on the animal production and feed-quality results from this experiment. There was a higher per head animal production for the P01 than the P20, with the P04 being intermediate. The differences were found for ewe liveweight and fat score, lamb growth rates and lamb liveweight at weaning. The P20 was able to run higher ewe numbers, in response to greater feed on offer than for P04 and P01, which enabled lamb production per hectare at weaning to be similar and greasy wool production per hectare to be greater than for P01. The organic matter digestibility of the ewe diet estimated from faecal analysis was lower for P20 and P04 systems than for P01 over a 7-month period and explained differences measured in sheep performance at that time. When lambs were retained after weaning, they could be kept for longer on the P20 and grown to a greater weight than for the P01 and P04, but the criteria for setting stocking rates and selling lambs from systems influenced the production from the systems. Further work is needed to investigate the interaction between stocking rate (ewe numbers and lamb sale time) and grazing management and examine different options for managing rotational grazing systems.
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Geenty, K. G., F. D. Brien, G. N. Hinch, R. C. Dobos, G. Refshauge, M. McCaskill, A. J. Ball et al. "Reproductive performance in the Sheep CRC Information Nucleus using artificial insemination across different sheep-production environments in southern Australia". Animal Production Science 54, n.º 6 (2014): 715. http://dx.doi.org/10.1071/an11323.
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The present paper covers reproductive performance in an artificial-insemination (AI) program of the Sheep CRC Information Nucleus with 24 699 lambs born at eight locations in southern Australia across five lambings between 2007 and 2011. Results from AI with frozen semen compared well with industry standards for natural mating. Conception rates averaged 72%, and 1.45 lambs were born per ewe pregnant for Merino ewes and 1.67 for crossbreds. Lamb deaths averaged 21% for Merino ewes and 15% for crossbreds and 19%, 22% and 20% for lambs from ewes that were mated to terminal, Merino and maternal sire types, respectively. Net reproductive rates were 82% for Merino ewes and 102% for crossbreds. From 3198 necropsies across 4 years, dystocia and starvation-mismothering accounted for 72% of lamb deaths within 5 days of lambing. Major risk factors for lamb mortality were birth type (single, twin or higher order), birthweight and dam breed. Losses were higher for twin and triplet lambs than for singles and there was greater mortality at relatively lighter and heavier birthweights. We conclude that reproductive rate in this AI program compared favourably with natural mating. Lamb birthweight for optimum survival was in the 4–8-kg range. Crossbred ewes had greater reproductive efficiency than did Merinos.
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Nenadovic, Katarina, Nikola Cobanovic, Marijana Vucinic, Dejan Bugarski, Tomislav Mikus, Eva Voslarova, Manja Zupan-Semrov, Miroslav Kjosevski y Nedjeljko Karabasil. "Welfare and meat quality of lambs". Veterinarski glasnik, n.º 00 (2021): 6. http://dx.doi.org/10.2298/vetgl210126006n.
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Recently, in many parts of the world, greater importance has been given to lamb meat as well as to the intensive production of lamb and sheep, due to demand for this type of meat at affordable prices. In Serbia, similar to most European countries, the structure of total sheep meat production comprises about 70% lamb meat and 30% sheep meat. This study assessed resource-based measures on 11 dairy sheep farms and investigated, in a total of 30 lambs, the effects of sex, the presence of bruises and pneumonia in carcasses, and carcass and meat quality. Carcass (carcass length, thigh length, croup width, subcutaneous fat thickness, presence of bruises) and meat quality (pH, temperature, drip, thawing and cooking losses, color, and meat quality classes) traits were measured post mortem. The most common deficiencies on farms were high stocking density, poor hygienic conditions, dirty drinkers, and lack of outdoor access. Regarding sex differences, higher prevalences of carcass bruises and severe pneumonia were recorded in male lambs. Meat pH (pH45min), sensory color score, and prevalence of dark, firm and dry (DFD) meat were higher in lambs with carcass bruises. The occurrence of quality defects (DFD meat) was higher in lambs with severe pneumonia. It can be concluded that it is necessary to improve the welfare conditions on the lamb farms and pre-slaughter conditions in order to achieve better lamb meat quality.
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SORMUNEN-CRISTIAN, R. y L. JAUHIAINEN. "Feeding levels during the growing phase affect the production of primiparous Finnish Landrace ewes". Agricultural and Food Science 9, n.º 3 (3 de enero de 2000): 187–200. http://dx.doi.org/10.23986/afsci.5660.
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The effect of different feeding levels on the performance of primiparous ewes was studied in 31 Finnish Landrace ewes bred to lamb at the age of one year. Ewe lambs, initially weighing on average 19.2 kg (SEM 0.63), were placed on a low (L), standard (S) or high (H) level of feeding from 2 months of age to the end of mating and from 2 months pre-partum to the end of 8-week lactation. Changes in live weight were affected by the diet. During rearing, the ewe lambs on L diet gained significantly less (18.0 vs. 24.1 kg/lamb, P
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Maxwell, T. J., Mary D. Lloyd y I. A. Dickson. "Upland sheep production systems". BSAP Occasional Publication 10 (1985): 95–105. http://dx.doi.org/10.1017/s0263967x00030780.
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AbstractUpland sheep production systems based on the utilisation of enclosed sown pastures are considered in relation to environmental constraints, recent trends in marketing requirements and a continuing need to improve economic efficiency. The need for quantitatively described decision making in relation to both the testing, development and application of new technology is discussed with particular reference to those factors influencing herbage growth, utilisation and management.Relatively few upland farms are capable of producing marketable fat lambs before the decline in returns per kg lamb in June. Although higher returns for heavier fat or store lambs can be obtained in the autumn, the degree to which this maximizes the returns per ha will be dependent upon the stocking rate and ewe and lamb performance during the summer. It will also be dependent on the extent to which there is competition for pasture in the autumn and its effect on ewe live weight and condition during the pre-mating and post-mating period; weight and condition will affect reproductive performance which has a substantial effect on returns per ha.The significance of sward height as a means of controlling the performance of sheep grazing sown pastures is reviewed in relation to ongoing and completed systems experiments and development projects. It is concluded that, for practical purposes, a sward height held between 3.5 and 5.5 cm will provide a sound basis for management of the lactating ewe and suckling lamb until weaning. The means of achieving sward height control in varying farming situations and the development of commercially viable management systems is considered.In the development of systems towards improving production efficiency, a better description of responses to both level and pattern of N used is required. The need for a better understanding of responses of the ewe in terms of ovulation rate and embryo wastage to changing sward characteristics in the autumn and to the use of supplementary feeding is also required. New techniques, such as the endocrine manipulation of reproductive performance, need to be assessed in relation to existing practices and performance.
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Malik, RC, MA Razzaque, S. Abbas, T. Al-Mutawa y N. Al-Khozam. "Breeding Australian crossbred ewes with Arabian fat-tailed rams for intensive lamb production". Australian Journal of Experimental Agriculture 36, n.º 1 (1996): 31. http://dx.doi.org/10.1071/ea9960031.
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The reproductive performance under intensive management of Border Leicester x Merino (BLM), Dorset x Merino (DM), and Suffolk x Merino (SM) ewes imported from Australia, and local fat-tailed Naeemi (N) ewes mated to N rams was studied. Progeny performance for birth and weaning weights, average daily gain (ADG) and preweaning survival was also evaluated. BLM ewes showed the highest reproductive performance. They produced and weaned (at 8 weeks) significantly more lambs (P<0.05) than any of the other ewe genotypes. The reproductive performance of the BLM, N, DM and SM ewes, mated twice, 8 months apart, was 127, 85, 91 and 85 respectively for percentage of lambs born to ewes joined, 109, 72, 77 and 70 respectively for percentage of lambs weaned to ewes joined, and 17.8, 13.5, 12.1 and 11.6 kg respectively of lamb weaned per ewe joined over the period of 13 months from the first joining until last lambs weaned. The effect of season on ewe reproduction was significant. Birth weight was not influenced by genotype or season but did change significantly with litter size. Genetic group, litter size, season of birth and birth weight were significant sources of variation in the ADG and weaning weight of the lamb. N x BLM lambs were weaned at significantly heavier weights than lambs of the remaining 3 groups. Season of birth and birth weight also significantly affected preweaning lamb survival. About 86% of the lambs born alive were weaned with little difference between genetic groups in survival rates.
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Fogarty, N. M. y J. G. Mulholland. "Seasonal reproductive performance of crossbred ewes in intensive lamb-production systems". Animal Production Science 54, n.º 6 (2014): 791. http://dx.doi.org/10.1071/an12434.
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The lambing performance of 1179 crossbred ewes with 5540 joining records in three seasons (autumn, winter and spring) at two sites (Cowra and Wagga Wagga) was evaluated in three lamb-production systems (spring joining with autumn backup matings at both locations, with accelerated lambing at Cowra or annual autumn joining at Wagga Wagga) over 4 years. Two genotypes of ewes, Border Leicester × Merino (BLM) and Hyfer (Dorset × Merino composite), were used at both sites, with natural matings to Dorset, Suffolk or Hyfer rams. The following five traits were analysed separately at each site to evaluate ewe lambing performance: fertility, litter size, lambs born (per ewe joined), lambs weaned (per ewe joined) and weight of lamb weaned (per ewe joined). The mixed model included fixed effects for season of joining, ewe breed, ram group, ewe prejoining weight (spline) and their interactions, with ewe fitted as a random effect. The autumn (February) joinings had higher ewe fertility, litter size and overall lamb production than did joinings in spring (October and November), with winter (June) being intermediate. At the autumn joinings, the BLM ewes had higher fertility, lambs weaned and weight of lamb weaned than did the Hyfer ewes, although this was reversed at the spring joinings, causing significant season × ewe breed interactions. While litter size was larger in the autumn than in the spring for both breeds there was a much smaller seasonal effect among the Hyfer than BLM ewes. Prejoining ewe weight had a significant effect on all reproduction traits, with generally a curvilinear response with increasing weight. The interactions of weight with season × ewe breed were significant (P < 0.001) for all traits at Cowra and most traits at Wagga Wagga. Ram group was significant (P < 0.05) for most traits, with ewes joined to Hyfer rams having higher fertility than those joined to Suffolk. and with Dorset rams being intermediate. At Wagga Wagga, this was the case for spring joinings, but there was no difference between the ram groups in autumn, causing a significant ram × season interaction (P < 0.001). Ewe repeatability ranged from 0.15 to 0.25 for all traits. Using suitable breeds or genotypes, together with optimising management, could improve out-of-season lamb production.
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King, Margaret E. y Beverley J. Keeling. "Lamb Production from Summer Lambing Ewes". Proceedings of the British Society of Animal Production (1972) 1987 (marzo de 1987): 85. http://dx.doi.org/10.1017/s0308229600035200.
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The majority of lamb production in Britain is concentrated in March and April resulting in a glut of lambs during July-September when the guaranteed price is at its lowest. Trials were carried out over 3 years to assess the feasibility of lambing hill and lowground ewes in early summer when grass is at its most productive and little concentrates are necessary prior to lambing.Trial 1 involved 20 bought-in Blackface (BF) ewes which were exposed to the tup in January/February in a sheltered field. Hay was available but no concentrates were fed. Ewes were outwintered and lambed in June/July when they were moved onto clean grazing. Concentrates were fed at the rate of 150g/d rising to 300g/d from 4 weeks pre-lambing to 10 days post-lambing. Results are shown in table 1.
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Minter, C. M., G. Perrott y E. Legendre. "The effect of feeding varying levels of barley and dried molassed sugar beet feed compared to a commercial creep on the performance of intensively reared Iambs". Proceedings of the British Society of Animal Science 1996 (marzo de 1996): 164. http://dx.doi.org/10.1017/s1752756200593594.
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Feed is the major cost of indoor lamb production, it accounts for up to £12/lamb reared (MLC, 1994) which is equivalent to 23% of the output value. Most intensively produced lambs are fed expensive specially formulated lamb creep diets. The aim of this experiment was to evaluate the effect varying the proportions of the starch (barley, WB) and digestible fibre (dried molassed sugar beet feed; SBF) and a protein pellet compared to a commercial lamb creep (LC) on lamb physical and financial performance.180 early weaned lambs, (weaned at 6 weeks of age), weighing on average 17.5 kg liveweight were allocated to one of six treatments; 0% SBF, 20% SBF, 40% SBF, 60% SBF, 80% SBF and LC. Each diet contained 20% protein balancer pellets with the remainder being whole barley. The LC diet was offered alone.
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Minter, C. M., G. Perrott y E. Legendre. "The effect of feeding varying levels of barley and dried molassed sugar beet feed compared to a commercial creep on the performance of intensively reared Iambs". Proceedings of the British Society of Animal Science 1996 (marzo de 1996): 164. http://dx.doi.org/10.1017/s0308229600031305.
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Feed is the major cost of indoor lamb production, it accounts for up to £12/lamb reared (MLC, 1994) which is equivalent to 23% of the output value. Most intensively produced lambs are fed expensive specially formulated lamb creep diets. The aim of this experiment was to evaluate the effect varying the proportions of the starch (barley, WB) and digestible fibre (dried molassed sugar beet feed; SBF) and a protein pellet compared to a commercial lamb creep (LC) on lamb physical and financial performance.180 early weaned lambs, (weaned at 6 weeks of age), weighing on average 17.5 kg liveweight were allocated to one of six treatments; 0% SBF, 20% SBF, 40% SBF, 60% SBF, 80% SBF and LC. Each diet contained 20% protein balancer pellets with the remainder being whole barley. The LC diet was offered alone.
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THOMAS, V. M., E. AYERS, K. HANFORD y R. KOTT. "INFLUENCE OF LASALOCID ON THE PRODUCTION OF GESTATING EWES IN AN EXTENSIVE GRAZING SYSTEM". Canadian Journal of Animal Science 68, n.º 2 (1 de junio de 1988): 439–44. http://dx.doi.org/10.4141/cjas88-049.
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A winter feeding trial was conducted to evaluate the influence of lasalocid (L) on the production of gestating ewes in an extensive grazing system. Six hundred and sixty ewes were randomized within age and breed and allotted to feed supplements (0.23 kg head−1 d−1) containing either no L (C) or L at 308 mg kg−1 and fed for 84 d during gestation. Ewe weight change within periods (three, 28-d periods) was similar (P > 0.10) with the exception of period 2 where L-supplemented ewes tended to gain more (P < 0.10) weight than C ewes. Total ewe weight change during the wintering period and yearly wool production were not affected (P > 0.10) by treatment. Treatment had no affect (P > 0.10) on the percentage or kilograms of lamb weaned for ewes starting the experiment. Ewes suckling twins and fed L during gestation had less (P < 0.05) lambs bummed (lamb removed from the ewe and sold) or grafted (lamb removal from the ewe and raised by a foster mother) than those in C group and suckling twins. In conclusion, providing L in a supplement to gestating ewes grazing winter range did not significantly alter production with the exception of less twin born lambs being bummed or grafted. Key words: Sheep, lasalocid, gestation, winter range, ewe, lamb
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Gascoigne, Emily y Peers Davies. "An approach to neonatal lamb post-mortem examinations". Livestock 24, n.º 4 (2 de julio de 2019): 193–98. http://dx.doi.org/10.12968/live.2019.24.4.193.
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Neonatal lamb mortality is a significant threat to welfare and production in commercial sheep flocks and is defined as the death of lambs during the first week of life with the predominant risk period being the first 48 hours. Lamb mortality between scanning and sale ranges from 10 to 25%, with examples of losses between 0 to 48 hours old ranging from 5.9% to 12.5%. Lamb post-mortem examinations are a tool which can facilitate achieving further understanding of the scale and cause of losses for flocks. We discuss an approach to postmortem examinations on neonatal lambs, the common differentials affecting lambs between 0 and 48 hours old, and discuss the role of farmers in surveillance.
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Ridler, Anne L., Kate J. Flay, Paul R. Kenyon, Hugh T. Blair, Rene A. Corner-Thomas y Emma J. Pettigrew. "Factors Associated with Mortality of Lambs Born to Ewe Hoggets". Animals 12, n.º 3 (28 de enero de 2022): 319. http://dx.doi.org/10.3390/ani12030319.
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The reproductive performance of ewe hoggets is poorer than that of mature-age ewes due to production of fewer lambs with poorer survival. Scant data are available on the risk factors for, and causes of, the mortality for lambs born to ewe hoggets, the impact of ewe deaths on lamb loss, and the causes of death for lambs born to ewe hoggets vs. mature-age ewes lambing in the same circumstances. In this study, 297 lambs born to 1142 ewe hoggets were necropsied along with 273 lambs born to 1050 mature-age ewes. Low lamb birthweight, multiple litter size, and increasing ewe hogget average daily gain from breeding to late pregnancy were risk factors for lamb mortality. The most common cause of mortality for lambs born to ewe hoggets was stillbirth and the risk factors for stillbirth were similar to those for lamb mortality generally. Approximately 11% of ewe hoggets’ lamb deaths were due to the death of the dam. Causes of mortality differed between lambs born to ewe hoggets vs. those born to mature-age ewes. Management practices to increase ewe hogget lambs’ birthweights (particularly those from multiple litters) and supervision of ewe hoggets at lambing time are recommended.
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Wildeus, Stephan y Dahlia O’Brien. "142 Reproductive performance of land race hair sheep ewes in different breeding seasons under a semi-continuous production". Journal of Animal Science 98, Supplement_2 (1 de noviembre de 2020): 76. http://dx.doi.org/10.1093/jas/skz397.178.
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Abstract A system for semi-continuous lamb production was evaluated using Barbados Blackbelly and St. Croix hair sheep ewes under 8-mo accelerated mating. Ewes were managed in a forage-based production system using rotational grazing. Two flocks of ewes (n = 30–35), equally representing the breeds, were bred 4 mo apart. Ewes were synchronized by feeding melengestrol acetate for 10 d, and mated in two single sire groups to like breed sires in November (NOV), March (MAR), and July (JUL) in a 25-d mating period. Pregnancy was recorded by transrectal ultrasound 22 d after breeding. Ewes were supplemented with corn/soybean meal during late gestation (0.75% of BW) and during lactation (1.5% of BW). They lambed on pasture with limited supervision, and lambs were weaned at 2 mo of age. Lambs had access to the supplement provided to ewes. Ewe performance (pregnancy rate, litter size, lamb survival, and birth and weaning weight) was recorded during a 2 yr production cycle, and analyzed for the effect of mating season. Pregnancy rate was not statistically different (P > 0.1) between season, and ranged from 93.9% in NOV, to 85.9 and 86.6% in MAR and JUL. Litter size (lambs born/ewe lambing) was higher (P < 0.05) in NOV (2.09) than MAR (1.68) and JUL (1.82). Lamb survival at birth was reduced (P < 0.001) in JUL (86.5%) compared to NOV (99%) and MAR (100 %), but was not different between seasons for survival to weaning (86 to 90%). Lamb birth weights were higher (P < 0.05) in MAR (3.16 kg) than JUL (2.99 kg), with NOV (3.05 kg) intermediate, while lamb weaning weights were higher (P < 0.001) in NOV (13.6 kg) compared with MAR (11.9 kg) and JUL (11.4 kg) mating. Data suggest that dual flock, accelerated mating of landrace hair sheep ewes can produce lamb cohorts of similar size in 4 mo intervals under a low-input, forage-based production system.
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Annett, R. W. y A. F. Carson. "Effect of digestible undegradable protein (DUP) concentration of concentrates offered to ewes on grass-based diets in late pregnancy on colostrum production and lamb performance". Proceedings of the British Society of Animal Science 2003 (2003): 59. http://dx.doi.org/10.1017/s1752756200012187.
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Nutrition of ewes during late pregnancy is a key factor influencing lamb survival and subsequent lamb growth and performance. Results from on-farm trials indicate that the superior lamb output from highly prolific compared with moderately prolific ewe breed types is less in grass-based compared with indoor lambing systems (Carson and Dawson, 2002). This is as a result of higher mortality rates of triplet lambs in outdoor systems with lower levels of intervention. Feeding and management strategies to maximise lamb viability for multiple births are required for grass-based lambing systems. Protein nutrition is likely to be a key factor, particularly considering that energy intakes in late pregnancy in triplet-bearing ewes are unlikely to meet requirements (Robinson, 1983). At sub-optimal energy intakes the supply of rumen undegraded protein is a major determinant of colostrum production and lamb birth weight. The objectives of this experiment were to investigate the effect of supplementing grass-based diets with concentrates with a range of digestible undegradable protein concentrations on colostrum production and lamb output.
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Rezende, Vanessa, Gustavo L. Sartorello, Beatriz Q. Reis, Guilherme Boldrin, Laya Alves, Danny Moreno, Miguel Souza, Camila Raineri y Augusto H. Gameiro. "PSXI-13 Effect of performance indicators, food expenses and interest rate on lamb production cost". Journal of Animal Science 98, Supplement_4 (3 de noviembre de 2020): 393. http://dx.doi.org/10.1093/jas/skaa278.691.
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Abstract This study aimed at comparing the influence of zootechnical performance and main cost items over the total production cost of lambs. A representative production system of São José do Rio Preto region, Brazil, designed in a panel meeting, was used as a study basis. We calculated lamb production costs, including variable costs, fixed costs, and income of factors, using the data from December 2019. We then estimated elasticities for the variables: feed expense, interest rate, carcass yield, lamb survival rate, and fertility rate. This way we compared the variation in total cost per year and per carcass caused by increases of 1% in each of the considered variables. In the base scenario, production costs per year and unit were, respectively, US$ 33,367.34 and US$ 4.81. Feed expenses, annual interest rate, mean carcass yield, lamb survival rate, and fertility rate were, respectively, US$ 22,316.74, 4.50%, 48.00%, 88.00%, and 85.00%. Regarding annual cost, changing each variable caused variations of +0.67%, +0.05%, 0.00%, +0.33% and +0.33%. Concerning cost per unit, the variations were +0.76%, +0.07%, -0.98%, -0.61% and -0.64%, respectively. Increasing lamb survival and fertility rates were also effective strategies to lower unitary cost. The cost component with feed represented 66.88% of the total production cost, but measures to reduce feed costs must be well conducted to not affect the zootechnical performance of the animals. Farmers must consider cost per unit when thinking about lowering production costs, instead of the annual cost. Increasing lamb carcass yield had a greater impact on reducing unitary cost than cutting feed expenses. Improving performance indicators demand good nutritional status for lambs and ewes, and cutting off feed expenses may have deleterious effects on animal performance, therefore increasing cost. Elasticity analysis is a useful tool to calculate such trade-offs at the farm level.
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Fogarty, NM, DG Hall y WR Atkinson. "Productivity of three crossbred ewe types mated naturally at 8-monthly intervals over two years". Australian Journal of Agricultural Research 43, n.º 8 (1992): 1819. http://dx.doi.org/10.1071/ar9921819.
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Productivity is reported for 175 Booroola MerinoxPoll Dorset (BD), 288 Trangie Fertility MerinoxPoll Dorset (TD) and 248 Border LeicesterxMerino (BLM) ewes joined three times (February, October and June) in 2 years. Overall joining in February resulted in higher performances (153�3% lambs born, 118�3% lambs weaned, 24.7�0.6 kg weight of lamb weaned, per ewe joined) than were obtained following October and June joinings (129�4% born, 93�3% weaned, 15.3�0.5 kg weight weaned per ewe joined). The mean number of lambings per year was 1.28�0.02 with an annual lambing rate of 211�4% lambs born and 160�3% lambs weaned. For lambs born, BD ewes were consistently higher than the other ewes, with BLM ewes having fewer lambs born from October and June joinings (P < 0.01). From the October joining, TD ewes had a higher weaning rate than BD ewes which were higher than BLM ewes (P < 0.01), but ewe type was not significant for the other two joinings. Over the three joinings there were no differences between the ewe types in the number of lambings per year or percentage of lambs weaned, but BD had more lambs born (239� 7%) than TD (212�5%) and BLM (181�5%). Analyses of the components of reproduction that contributed to overall lamb production showed that although more than 95% of ewes expressed oestrus in each season, fertility and litter size were higher from the February joining, while lamb survival was lower following the June joining. Ewe crossbred type was significant (P < 0.01) for litter size in all seasons. Litter size for BD ewes was 1.9 to 2.0, and for TD ewes was 1.6 to 1.7 at all seasons, while that for BLM ewes was 1.7 from February and 1.2 and 1.4 from October and June joinings respectively. The effects of ewe liveweight at joining and liveweight gain over joining were variable over the three joinings, but were generally small. BD ewes carrying the F gene tended to have a higher percentage of lambs born and lower percentage of lambs weaned than non-carriers. There was also a decline in lamb production, especially fertility and lamb survival, with ewe age among BD and TD ewes. Implications for production systems in the lamb industry are discussed.
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Blackburn, H. D., G. D. Snowder y H. Glimp. "Simulation of lean lamb production systems." Journal of Animal Science 69, n.º 1 (1991): 115. http://dx.doi.org/10.2527/1991.691115x.
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Gascoigne, Emily y Fiona Lovatt. "Lamb growth rates and optimising production". In Practice 37, n.º 8 (septiembre de 2015): 401–14. http://dx.doi.org/10.1136/inp.h4537.
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Glimp, Hudson A. y Frank H. Baker. "Lamb Production Systems for Increasing Productivity". Professional Animal Scientist 2, n.º 2 (diciembre de 1986): 24–27. http://dx.doi.org/10.15232/s1080-7446(15)32430-x.
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