Artículos de revistas: "Australian merino sheep Physiology"

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

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

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Parsons, Y. M., D. W. Cooper, L. R. Piper, Y. M. Parsons y D. W. Cooper. "Genetic variation in Australian Merino sheep". Animal Genetics 27, n.º 4 (24 de abril de 2009): 223–28. http://dx.doi.org/10.1111/j.1365-2052.1996.tb00482.x.

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Board, P. G. "Erythrocyte oxidized glutathione in Australian Merino sheep". Animal Blood Groups and Biochemical Genetics 6, n.º 2 (24 de abril de 2009): 65–69. http://dx.doi.org/10.1111/j.1365-2052.1975.tb01353.x.

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Lakota, E. А. "PRESERVATION OF GENETIC POTENTIAL OF STAVROPOL SHEEP BREED FOR POVOLZHYE DREY STEPPE ZONE". Vestnik of Ulyanovsk state agricultural academy, n.º 3(50) (8 de septiembre de 2020): 179–84. http://dx.doi.org/10.18286/1816-4501-2020-3-179-184.

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In conditions of Povolzhye steppe zone development of productive qualities of Stavropol breed sheep was conducted by meat merino sheep. Experimental research was carried out in ZAO «Novaya Zhizn» in Novouzensky district of Saratov region, located in semi desert zone, bordering upon South-West Khazakhstan. The research aim was the increase and maintenance of genetic potential of Stavropol breed sheep of Povolzhye population. Working procedure is based on guidelines of the All-Union Academy of Agricultural sciences, All Union research institute of sheep and goat breeding. The study materials were Stavropol pure breed sheep and 1/8 –thoroughbred cross breed with Australian meat merino herdmates. As the result of stepped breeding of local Stavropol ewe with half bred by Australian meat merino ram- breeder of Stavropol breed animals of 1/2 ,1/4, 1/8 –blood were obtained, which then one- shear tupped by breeding «inter se». It is proved that in applying such selective method 1/8-blood by Australian meat merino sheep were characterized with higher body weight, better wool quality in contrast to Stavropol pure –breed herdmates. So, in 1/8-blood by Australian meat merino of hybrid ewe during breeding «inter se» live body at birth was higher than at pure breed herdmates for 5,56 %, during ablactation –at the age of 4 months - for 6,38 % (difference isn’t accurate). According to sharing of wool in grease, superiority of ewe of hybrid origin over pure breed was 5,6 % (Р≥0,99), but in terms of washed fiber it increases to 8,3 % (Р≥0,999). So, in dry steppe zone of Povolzhye new improved, according to its productive qualities, genotype of Stavropol breed sheep is created with retention of genetic resource that is essential economic factor for the modern maintenance of fine-wool sheep breeding field.

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Hatcher, S., K. D. Atkins y E. Safari. "Lamb survival in Australian Merino Sheep: A genetic analysis12". Journal of Animal Science 88, n.º 10 (1 de octubre de 2010): 3198–205. http://dx.doi.org/10.2527/jas.2009-2461.

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Behrendt, Karl. "Price risk exposure of Australian Merinos – is it in the bloodline?" Animal Production Science 54, n.º 9 (2014): 1317. http://dx.doi.org/10.1071/an14305.

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Sheep producers and their advisors utilise Australian Merino bloodline trial data to guide future sheep breeding objectives and ram selection. To adequately assess the economic outcomes from different bloodlines in the decision making process, there is a need to consider the impact of wool and sheep meat price risk. Using a steady-state wether flock model that accounts for the lifetime productivity of 268 reported Merino bloodlines and stochastic dependency in weekly wool and sheep meat prices from 28 June 2005 to 10 November 2011, gross incomes per dry sheep equivalent (GI/DSE) were calculated for a weekly time step. The analysis found that across all bloodlines and market price scenarios, GI/DSE ranged between AU$13.92 and AU$67.83, with an overall mean of AU$32.60. The individual means of bloodlines across the time series ranged from AU$37.46 to AU$25.19 GI/DSE. The coefficient of variation, used as the measure of relative risk for each bloodline, ranged from 0.24 to 0.30 with a mean of 0.25. The analysis showed that a bloodlines exposure to price risk has a curvilinear relationship to fibre diameter and fleece weight. The results from a risk-reward point of view indicate that the majority of Australian Merino bloodlines are risk-inefficient. This suggests Australian sheep producers have a significant opportunity to increase net returns and reduce price risk exposure by identifying and switching to more risk-efficient bloodlines.

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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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Parsons, Y. M., M. R. Fleet y D. W. Cooper. "The Agouti gene: a positional candidate for recessive self-colour pigmentation in Australian Merino sheep". Australian Journal of Agricultural Research 50, n.º 6 (1999): 1099. http://dx.doi.org/10.1071/ar98099.

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The occurrence of self-colour pigmentation in the Australian Merino wool flock is of considerable economic importance. The Agouti gene is believed to be responsible for the recessive expression of pigmented fleece. Using comparative mapping information we have investigated the putative homologous ovine map positon of the Agouti gene for linkage to the recessive self-colour phenotype of Australian Merino sheep. Significant results were observed with microsatellites previously mapped to ovine chromosome 13. Comparative data suggest that the ovine Agouti gene would map to the same chromosome, making the Agouti gene a positional candidate for the self-colour phenotype.

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Fortune, J. A. "Reproductive physiology of Merino sheep: Concepts and consequences". Animal Reproduction Science 30, n.º 4 (enero de 1993): 335–36. http://dx.doi.org/10.1016/0378-4320(93)90083-4.

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Huisman, A. E. y D. J. Brown. "Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 3. Genetic relationships between ultrasound scan traits and other traits". Animal Production Science 49, n.º 4 (2009): 283. http://dx.doi.org/10.1071/ea08172.

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The Australian Merino is the predominant genetic resource for both the lamb and sheep meat industries of Australia. There are very few studies that provide information on the relationships between wool and non-wool traits. This paper describes the genetic relationships between ultrasound scan traits and wool, disease resistance and reproduction traits in Merino sheep. Fleece weight and fibre diameter coefficient of variation were negatively correlated with ultrasound scanned fat and eye muscle depth (–0.10). Staple length, fibre curvature, and scrotal circumference were not correlated with scanned fat or eye muscle depth. Staple strength, number of lambs born and number of lambs weaned had a positive genetic correlation with fat and eye muscle depth (0.20–0.30). Faecal egg count had a negative genetic correlation with scanned fat (–0.10) and scanned eye muscle depth (–0.20). Results indicate that the combined improvement of carcass and wool characteristics in Merino sheep is possible.

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Tammen, Imke, Roger W. Cook, Frank W. Nicholas y Herman W. Raadsma. "Neuronal ceroid lipofuscinosis in Australian Merino sheep: a new animal model". European Journal of Paediatric Neurology 5 (enero de 2001): 37–41. http://dx.doi.org/10.1053/ejpn.2000.0432.

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Murray, J. D., C. Moran, M. P. Boland, C. D. Nancarrow, R. Sutton, R. M. Hoskinson y R. J. Scaramuzzi. "Polyploid cells in blastocysts and early fetuses from Australian Merino sheep". Reproduction 78, n.º 2 (1 de noviembre de 1986): 439–46. http://dx.doi.org/10.1530/jrf.0.0780439.

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

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

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Ponnampalam, E. N., K. L. Butler, D. L. Hopkins, M. G. Kerr, F. R. Dunshea y R. D. Warner. "Genotype and age effects on sheep meat production. 5. Lean meat and fat content in the carcasses of Australian sheep genotypes at 20-, 30- and 40-kg carcass weights". Australian Journal of Experimental Agriculture 48, n.º 7 (2008): 893. http://dx.doi.org/10.1071/ea08054.

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Lean meat and fat content of Australian sheep genotypes were compared at 20-, 30- and 40-kg carcass weights. Sheep comprised Poll Dorsetgrowth × Border Leicester Merino (PDg × BLM), Poll Dorsetgrowth × Merino (PDg × M), Poll Dorsetmuscling × Merino (PDm × M), Border Leicester × Merino (BL × M) and Merino × Merino (M × M) genotypes. Lambs were raised as a mixed flock under grazing and slaughtered at 4, 8, 14 and 22 months of age with each slaughter time involving ~150 mixed sex animals. At 24 h after slaughter, chilled carcasses were halved along the backbone and the right sides were used for determination of lean, fat and ash percentages using dual energy X-ray absorptiometry. Within a particular age group and genotype, animals growing at faster rates and reaching heavier carcass weights had lower carcass lean meat content than slower growing animals. Merino carcasses weighing 20 and 30 kg had similar levels of lean meat to PD × M genotypes, which was greater than that from the BL × M genotype. Second-cross PD × BLM carcasses weighing 20 kg at 4 months and 30 kg at 8 months had similar carcass fat and lean percentages to 20-kg Merino carcasses at 8 months and first-cross PD × M carcasses weighing 30 kg at 14 months, respectively. At 40-kg carcass weight, 22-month-old Merinos had similar levels of leanness to carcasses from 22-month-old PD × M animals and carcasses from 14-month-old second-cross PD × BLM animals. Carcass lean meat content decreased with increasing carcass weight and first- cross BL × M animals had the lowest carcass lean across all weight categories. There was a major acceleration in carcass fatness between 14 and 22 months associated with a reduction in muscle deposition. Results indicate that age of the animal should be taken into account when carcass lean and fat contents are compared at a particular carcass weight. Merinos will achieve weight/composition specifications at least equally well to crossbreds but will take longer with a likely increase in production costs.

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Britt, AG, CL Cotton, BH Kellett, IH Pitman y JA Trask. "Structure of the Epidermis of Australian Merino Sheep Over a 12-Month Period". Australian Journal of Biological Sciences 38, n.º 1 (1985): 165. http://dx.doi.org/10.1071/bi9850165.

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Light-microscopic examination of frozen sections of skin taken from the dorsal thoraco-Iumbar region of Australian Merino sheep in winter revealed that the thickness of the epidermis plus a sudanophilic layer was 24�9 !tm in the interfollicular region. The uncornified epidermis (10�9 !till) was separated from the sudanophilic layer (14�0 !tm) by a thin stratum corneum. It was concluded that the bulk of the sudanophilic layer was emulsified sebum in which was embedded a disorganized collection of desquamated cornified cells. Although large variances were observed in the thickness of the uncornified epidermis and of the sudanophilic layers between sheep and both within the between blocks of tissue obtained from individual sheep, there were no strong seasonal effects on either epidermal structure or layer thickness over a 12-month period. These results suggest that the Australian Merino differs from Finnish Landrace x Dorset Horn ewes, which are reported to possess, at least in winter, a thicker uncornified epidermis and a thicker stratum corneum that could be divided into two zones and was uniformly permeated by lipid.

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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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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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LUSHNIKOV, V. P. "MEAT PRODUCTIVITY OF RAMS OBTAINED BY CROSSING VOLGOGRAD SHEEPS WITH RAMS OF DIFFERENT FOREIGN BREEDS". Sheep, goats, woolen business, n.º 2 (2021): 23–25. http://dx.doi.org/10.26897/2074-0840-2021-2-23-25.

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The article presents the indicators of slaughter, morphological and chemical composition of lamb meat obtained from industrial crossing of Volgograd breed queens with sheep breeds: Poll Dorset, Australian meat merino, North Caucasian meat-wool, Suff olk, Ile-de-France and Merinoland.

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Daetwyler, H. D., J. M. Hickey, J. M. Henshall, S. Dominik, B. Gredler, J. H. J. van der Werf y B. J. Hayes. "Accuracy of estimated genomic breeding values for wool and meat traits in a multi-breed sheep population". Animal Production Science 50, n.º 12 (2010): 1004. http://dx.doi.org/10.1071/an10096.

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Estimated breeding values for the selection of more profitable sheep for the sheep meat and wool industries are currently based on pedigree and phenotypic records. With the advent of a medium-density DNA marker array, which genotypes ~50 000 ovine single nucleotide polymorphisms, a third source of information has become available. The aim of this paper was to determine whether this genomic information can be used to predict estimated breeding values for wool and meat traits. The effects of all single nucleotide polymorphism markers in a multi-breed sheep reference population of 7180 individuals with phenotypic records were estimated to derive prediction equations for genomic estimated breeding values (GEBV) for greasy fleece weight, fibre diameter, staple strength, breech wrinkle score, weight at ultrasound scanning, scanned eye muscle depth and scanned fat depth. Five hundred and forty industry sires with very accurate Australian sheep breeding values were used as a validation population and the accuracies of GEBV were assessed according to correlations between GEBV and Australian sheep breeding values . The accuracies of GEBV ranged from 0.15 to 0.79 for wool traits in Merino sheep and from –0.07 to 0.57 for meat traits in all breeds studied. Merino industry sires tended to have more accurate GEBV than terminal and maternal breeds because the reference population consisted mainly of Merino haplotypes. The lower accuracy for terminal and maternal breeds suggests that the density of genetic markers used was not high enough for accurate across-breed prediction of marker effects. Our results indicate that an increase in the size of the reference population will increase the accuracy of GEBV.

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Cottle, D. J., M. T. Harrison y A. Ghahramani. "Sheep greenhouse gas emission intensities under different management practices, climate zones and enterprise types". Animal Production Science 56, n.º 3 (2016): 507. http://dx.doi.org/10.1071/an15327.

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Greenhouse gas emissions (GHG) from broadacre sheep farms constitute ~16% of Australia’s total livestock emissions. To study the diversity of Australian sheep farming enterprises a combination of modelling packages was used to calculate GHG emissions from three sheep enterprises (Merino ewe production for wool and meat, Merino-cross ewes with an emphasis on lamb production, and Merino wethers for fine wool production) at 28 sites across eight climate zones in southern Australia. GHG emissions per ha, per dry sheep equivalents and emissions intensity (EI) per tonne of clean wool or liveweight sold under different pasture management or animal breeding options (that had been previously determined in interviews with farmers) were assessed relative to baseline farms in each zone (‘Nil’ option). Increasing soil phosphorus fertility or sowing 40% of the farm area to lucerne resulted in the smallest and largest changes in GHG/dry sheep equivalents, respectively (–66%, 113%), though both of these options had little influence on EI for either clean wool or liveweight sold. Breeding ewes with greater body size or genotypes with higher fleece weight resulted in 11% and 9% reductions, respectively, in EI. Enterprises specialising in lamb production (crossbred ewes) had 89% lower EI than enterprises specialising in fine wool production (Merino wethers). Thus, sheep producers aiming for lower EI could focus more on liveweight turnoff than wool production. Emissions intensities were typically highest in cool temperate regions with high rainfall and lowest in semiarid and arid regions with low aboveground net primary productivity. Overall, animal breeding options reduced EI more than feedbase interventions.

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Haba, M. De La, A. Moreno, D. Llanes y E. M. Tucker. "Glutathione concentrations in the red cells of Merino sheep". Journal of Agricultural Science 110, n.º 2 (abril de 1988): 401–3. http://dx.doi.org/10.1017/s002185960008148x.

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Tasmanian Merino sheep show a bimodal distribution in the concentration of reduced glutathione (GSH) in their red cells, 40% of sheep having GSH values of around 27 mg GSH/100 ml red cells and 60% with values of about 92 mg GSH/100 ml red cells (Tucker & Kilgour, 1972). The GSH deficiency was shown to be due to an impaired activity of γ-glutamyl cysteine synthetase (γ-GC-S), the enzyme catalysing the first step of GSH biosynthesis (Tucker, Kilgour & Young, 1976). Family data indicated that the deficiency in this strain of Merinos was under the control of a dominant gene, designated GSHL (Tucker et al. 1976). In contrast, Board, Roberts & Evans (1974) reported that a similar type of GSH deficiency in Australian Merino sheep was under the control of a recessive gene. The reasons for this apparent discrepancy remain unresolved.

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Al-Atiyat, R., W. Flood, I. Franklin, B. Kinghorn y A. Ruvinsky. "Microsatellite-based genetic variation and differentiation of selected Australian Merino sheep flocks". Small Ruminant Research 136 (marzo de 2016): 137–44. http://dx.doi.org/10.1016/j.smallrumres.2016.01.018.

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FLANAGAN, M., SJ JOHNSON, D. HOFFMANN, IG POLKINGHORNE, DJ REID y MA SHEPHERD. "Clinical pathology of Australian bluetongue virus serotype 16 infection in Merino sheep". Australian Veterinary Journal 70, n.º 3 (marzo de 1993): 101–4. http://dx.doi.org/10.1111/j.1751-0813.1993.tb03286.x.

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Fogarty, N. M., E. Safari, P. J. Taylor y W. Murray. "Genetic parameters for meat quality and carcass traits and their correlation with wool traits in Australian Merino sheep". Australian Journal of Agricultural Research 54, n.º 7 (2003): 715. http://dx.doi.org/10.1071/ar03047.

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Estimates of genetic parameters for carcass traits in Merino sheep are presented, including muscle pH and colour, which are indicators of meat quality. The inclusion of these in the parameter set for genetic evaluation will provide the basis for more accurate estimated breeding values and the design of better breeding programs for improving meat traits in straightbred Merino sheep and crossbred lamb production. Data from 1045, nineteen-month-old Merino rams, the progeny of 125 sires from 3 strains that are representative of the industry, were used. Heritability and genetic correlations were estimated by fitting an animal model using a REML procedure in univariate and multivariate analyses. The traits included fasted pre-slaughter liveweight; dressing %; carcass tissue depth at the GR site (FATGR); fat depth at the C site (FATC); eye muscle depth (EMD), width (EMW), and area (EMA); ultimate pH and colour (L*, a*, b*) of the eye muscle. Multivariate analyses were used to estimate genetic correlations among meat traits and between wool traits (clean wool weight and mean fibre diameter) and selected carcass and meat traits. Estimates of heritability were: liveweight 0.51 (±0.10), dressing % 0.39 (±0.10), FATGR 0.33 (±0.09), FATC 0.20 (±0.08), EMD 0.27 (±0.08), EMW 0.15 (±0.07), EMA 0.23 (±0.08), muscle pH 0.27 (±0.09), and 0.14 (±0.07), 0.02 (±0.06), and 0.04 (±0.06) for the meat colour measurements L*, a*, and b* respectively. There was a favourable genetic correlation between muscle pH and colour L* of –0.56 (±0.23). There were also significant genetic correlations between wool weight and FATGR (–0.34 ± 0.16) and between mean fibre diameter and muscle colour L* (–0.66 ± 0.27). The study indicates that there is genetic variation for carcass traits, including indicators of meat quality, with scope for selection to improve meat production and quality in Merino sheep.

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26

Mortimer, S. I., K. D. Atkins, S. J. Semple y N. M. Fogarty. "Predicted responses in Merino sheep from selection combining visually assessed and measured traits". Animal Production Science 50, n.º 10 (2010): 976. http://dx.doi.org/10.1071/an10085.

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Visually assessed traits for wool quality and ease of management are important to Merino sheep breeders and need to be considered in breeding programs. The present study reports on the predicted correlated responses in visual traits from selection using a range of standard MERINOSELECT™ indices available for use in Australian Merino breeding programs. The effect of including a visual trait in the index is also reported. The visual scored traits were classer grade, wool quality (handle, character and colour), conformation (neck and body wrinkle, front and back leg structure) and fleece rot. The indices covered a range of micron premiums of varying emphasis on increasing fleece weight and reducing fibre diameter. The indices were for Merino wool enterprises (Merino 14%, Merino 7% and Merino 3.5%) and Merino dual purpose wool and meat enterprises (Dual Purpose 7% and Dual Purpose 3.5%). The breeding objectives for the indices included fleece weight, fibre diameter, coefficient of variation of fibre diameter, staple strength, bodyweight and reproduction. Selection over 10 years using the standard MERINOSELECT™ indices is predicted to result in a small correlated improvement in the wool quality traits and classer grade, with a slight deterioration in fleece rot score. The improvement in wool handle, character and colour are greater with those indices that have a greater emphasis on reducing fibre diameter than with those increasing fleece weight. Indices with more emphasis on increased fleece weight than on reduced fibre diameter are predicted to result in small increases in neck and body wrinkle scores and a slight deterioration in wool colour. Inclusion of classer grade, handle, character or colour provided slight extra gains in fleece weight for indices that emphasised reduced fibre diameter through increased accuracy of selection.

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27

Hutchison, Dayna, Bronwyn E. Clarke, Serina Hancock, Andrew N. Thompson, Elise Bowen y Caroline Jacobson. "Lower Reproductive Rate and Lamb Survival Contribute to Lower Lamb Marking Rate in Maiden Ewes Compared to Multiparous Ewes". Animals 12, n.º 4 (18 de febrero de 2022): 513. http://dx.doi.org/10.3390/ani12040513.

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Suboptimal reproductive performance of maiden (primiparous) ewes remains a source of inefficiency for the Australian sheep industry. However, the extent and causes of the poorer reproductive performance of maiden ewes on Australian sheep farms are not well understood. Here, we show the reproductive performance of maiden ewes relative to their multiparous counterparts on the same farms across Australia using a cohort survey. The difference in marking rate for non-Merino maiden ewe lambs compared to multiparous ewes was 58% (74 vs. 132%; p < 0.001), and this was attributable to a 50% difference in reproductive rate (109 vs. 159%; p < 0.001) and 16% difference in lamb survival to marking (67 vs. 83%; p < 0.001). The difference in marking rate for maiden Merino two-tooth ewes lambing at approximately 2 years-of-age compared to mature multiparous ewes was 22% (80 vs. 102%; p < 0.001) and this was attributable to a 24% difference in reproductive rate (108 vs. 132%; p < 0.001) and 3% difference for lamb survival (75 vs. 78%; p < 0.05). Positive correlations for reproduction traits (reproductive rate, lamb survival and marking rate) between maidens and multiparous ewes were observed for maiden Merino two-tooth ewes (p < 0.001), but these correlations were weak or non-existent for non-Merino ewe lambs. Strategies to improve both reproductive rate and lamb survival can address the poorer and more variable reproductive performance of maiden ewes.

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28

Britt, AG, CL Cotton, IH Pitman y AN Sinclair. "Effects of the Sheep-Chewing Louse (Damalinia ovis) on the Epidermis of the Australian Merino". Australian Journal of Biological Sciences 39, n.º 2 (1986): 137. http://dx.doi.org/10.1071/bi9860137.

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Frozen longitudinal skin sections taken from the dorsal thoraco-lumbar region of adult Merino sheep that were infested with the sheep-chewing louse were examined by light microscopy. The epidermis of infested sheep exhibited acanthosis due to hyperplasia of the stratum spinosum, and orthokeratosis. The thicknesses of the uncornified epidermis, the stratum corneum, and the sudanophilic region were significantly greater (P < O� 005) than equivalent regions in louse-free Merinos and the results suggest that a positive correlation exists between the thickness of each region and the level of louse infestation. The results indicate that the variance in region thickness was greater in lousy than in louse-free sheep (P < 0'005).

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29

Fozi, M. Asadi, J. H. J. Van der Werf y A. A. Swan. "Modelling genetic covariance structure across ages of mean fibre diameter in sheep using multivariate and random regression analysis". Animal Production Science 52, n.º 11 (2012): 1019. http://dx.doi.org/10.1071/an12139.

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Mean fibre diameter measurements from yearling to 5-year-old Australian fine- and medium-wool Merino sheep were analysed using several multivariate models that varied in covariance structure. A pre-structured multivariate model was found to be the most parsimonious model in comparison with the other models fitted such as banded, autoregressive and random regression. In the preferred model, the ages of mean fibre diameter for fine-wool data were genetically partitioned into yearling, 2 years, 3 years and later ages and for medium-wool data into hogget, 2 years and later ages. The estimates of genetic correlations between mean fibre diameter measured at different ages for medium-wool sheep were higher (0.89–1.00) than those for fine-wool Merino (0.75–1.00).

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30

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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31

Qiu, Xiaoyan, Xiong Xiao, Nan Li, Wenhui Ling, Mingyu Wang y Yuemin Li. "Association of steroid 17-alpha-hydroxylase/17,20 lyase (CYP17) single nucleotide polymorphism (SNP) 628 and dopamine receptor D2 (DRD2) SNP939 genotypes with sheep reproductive performance". Reproduction, Fertility and Development 31, n.º 4 (2019): 743. http://dx.doi.org/10.1071/rd18069.

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In a previous study we investigated the association between two single nucleotide polymorphism (SNP) genotypes, namely steroid 17-alpha-hydroxylase/17,20 lyase (CYP17) SNP628 and dopamine receptor D2 (DRD2) SNP939, with two temperaments (calm and nervous) in Australian Merino sheep and concluded that the DRD2 SNP939 T/T genotype combined with the CYP17 SNP628 G/G genotype is associated with a calm temperament and could be used as a potential marker for calm sheep, whereas the DRD2 SNP939C allele combined with the CYP17 SNP628 A/A genotype is associated with a nervous temperament and could be used as a potential marker for nervous sheep. In sheep, the association between temperament and reproductive performance has been determined, but the association of these two SNP genotypes with sheep reproduction has not been investigated. Therefore, using Chinese Sinkiang Merino sheep, the present study investigated the association of the two CYP17 SNP628 and DRD2 SNP939 genotypes with sheep reproductive performance. Sheep with the DRD2 SNP939 T/T genotype combined with the CYP17 SNP628 G/G genotype had a higher ovulation rate, multiple gestation rate, better maternal behaviour and lower lamb mortality. Thus, the results of this study contribute to our knowledge of the association between genotypes and reproduction in sheep, which is beneficial for sheep genetics and breeding.

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32

Ponnampalam, E. N., D. L. Hopkins, F. R. Dunshea, D. W. Pethick, K. L. Butler y R. D. Warner. "Genotype and age effects on sheep meat production. 4. Carcass composition predicted by dual energy X-ray absorptiometry". Australian Journal of Experimental Agriculture 47, n.º 10 (2007): 1172. http://dx.doi.org/10.1071/ea07008.

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This study compares the carcass composition of different genotypes of Australian sheep slaughtered at four ages (110, 236, 412 and 662 days of age, or 4, 8, 14 and 22 months of age). The genotypes used were 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). Approximately 150 mixed sex animals were slaughtered at each age and the right sides (half carcass) were scanned by dual energy X-ray absorptiometry (DXA) for chemical lean, fat and bone mineral percentages of the carcass. Carcass lean percentage decreased (P < 0.001) across sire groups from Merino to Poll Dorset to Border Leicester at each age, while fatness increased (P < 0.001) in the opposite direction. With age, the magnitude of difference between genotypes for fatness became greater. There was a marked increase (P < 0.01) in ash mineral percentages in M × M and PDg × M genotypes relative to other genotypes in the 14- and 22-month groups. There were no differences (P > 0.1) between PDg × M and PDm × M in either chemical lean or fat percentages at any age but ash mineral percentage was higher in the PDg × M genotype at older ages (P < 0.05). This in turn led to differences in chemical lean : ash mineral content at later ages between PDg × M and PDm × M. Wethers had higher chemical lean (P < 0.05) and lower fat (P < 0.05) percentages in the carcass than ewes at all ages but ash mineral and chemical lean : ash mineral content did not differ between sexes. It was clear that the level of chemical lean or fat or ash mineral composition reached by some genotypes at one age was equivalent to that reached by other genotypes at the next measurement age. Those genotypes that reach a specification at younger ages will be more productive for meat production. Purebred Merino genetics will always be less productive in terms of carcass weight and muscle related productive traits (loin weight, semitendinosus muscle weight, eye muscle area) than BL and PD genetics, but the relative productivity of PD and BL genetics will depend on the traits used in the specification [see also Ponnampalam EN, Hopkins DL, Butler KL, Dunshea FR, Warner RD (2007) Genotype and age effects on sheep meat production. 2. Carcass quality traits. Australian Journal of Experimental Agriculure 47, 1147–1154]. The results suggest that selection for muscling had a greater impact on reducing ash mineral content associated with bone mineral mass than on increasing lean mass in the carcass.

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33

Lakota, E. A. "Productivity of Stavropol sheep with Australian meat merino rocks in the Volga region". Agrarian science 322, n.º 2 (febrero de 2019): 42–43. http://dx.doi.org/10.32634/0869-8155-2019-322-2-42-43.

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34

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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35

Ponzoni, R. W. "Linear approximation of non-linear selection indices: an example with Australian Merino sheep". Journal of Animal Breeding and Genetics 102, n.º 1-5 (12 de enero de 1985): 395–99. http://dx.doi.org/10.1111/j.1439-0388.1985.tb00708.x.

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36

BOURKE, CA, MJ CARRIGAN y CHR DENT. "Chronic locomotor dysfunction, associated with a thalamic-cerebellar neuropathy, in Australian Merino sheep". Australian Veterinary Journal 70, n.º 6 (junio de 1993): 232–33. http://dx.doi.org/10.1111/j.1751-0813.1993.tb03315.x.

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37

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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38

Horton, B. J., R. Corkrey y A. K. Doughty. "Sheep death and loss of production associated with flystrike in mature Merino and crossbred ewes". Animal Production Science 58, n.º 7 (2018): 1289. http://dx.doi.org/10.1071/an16153.

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In eight well-managed Australian Merino and crossbred sheep flocks the adult ewes were monitored frequently for flystrike. Occurrences of flystrike and severity of strike scores were recorded, whereas bodyweights and condition scores were recorded regularly across two wool production and reproduction cycles. In these unmulesed flocks, 17% of Merino and 5% of crossbred ewes were struck, with 2% of those struck dead within 7 days of detection of the strike. For those adult ewes that survived the immediate period of the strike, the rate of loss over the following year was slightly greater than for ewes that were never struck, particularly for those with a high severity strike. Flystrike also contributed to losses of up to 2.7 (Merino ewes) and 5.2 (crossbred ewes) kg of bodyweight, and 0.3 condition score units at the time of the strike. Bodyweights were still 2 kg lower by 3 months after the strike occurred for Merinos, although condition scores returned to average levels. For ewes struck between mating and lambing, flystrike was associated with significant losses of lambs. Flystrike at severity level 1 (light) had only minor effects on wool production, but severity score 3 (heavy) reduced clean fleece weight.

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39

Huisman, A. E., D. J. Brown, A. J. Ball y H. U. Graser. "Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 1. Description of traits, model comparison, variance components and their ratios". Australian Journal of Experimental Agriculture 48, n.º 9 (2008): 1177. http://dx.doi.org/10.1071/ea08119.

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Both wool and sheep meat industries are interested in sheep that have a high reproduction performance and are resistant to internal parasites, in addition to the traditional traits. There is considerable interest in breeding sheep for wool, carcass, reproductive and internal parasite resistance traits simultaneously. The objective of this study was to estimate single trait genetic parameters for 40 traits recorded in Merino sheep, covering bodyweight, carcass, wool, reproduction and internal parasite resistance traits. This also involved determining the appropriate models. The results from this study will be used to review the genetic parameters used in the routine genetic evaluations conducted by Sheep Genetics. The most appropriate models included a maternal genetic effect and covariance between direct and maternal genetic effects for most of the bodyweight traits, greasy and clean fleece weight, fibre diameter and coefficient of variation of fibre diameter. The permanent environment due to the dam was not included for any trait. There was considerable genetic variation in most traits analysed; lowest heritabilities (0.09–0.10) were found for number of lambs born and weaned per lambing opportunity, and highest heritabilities (0.62–0.77) for fibre diameter. The estimated heritabilities and genetic variances, in combination with the estimated correlations, indicate that there is potential to make genetic improvement in most traits currently recorded in Australian Merino sheep.

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40

Huisman, A. E. y D. J. Brown. "Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 2. Genetic relationships between bodyweight traits and other traits". Australian Journal of Experimental Agriculture 48, n.º 9 (2008): 1186. http://dx.doi.org/10.1071/ea08120.

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The Australian Merino is the predominant genetic resource for both the prime lamb and sheep meat industries of Australia. There are very few studies that provide good information on the relationships between wool and non-wool traits. The objective of this paper was to describe genetic relationships within bodyweight traits and between bodyweight and other traits recorded in Merino sheep. The genetic correlation between bodyweight, fleece weight and fibre diameter was positive (0.1 to 0.2). While fibre diameter coefficient of variation, staple length, staple strength, mean fibre curvature, and faecal egg count were not correlated with bodyweight. Scrotal circumference (0.4), number of lambs born (0.1), and number of lambs weaned (0.1) were positively correlated with bodyweight. Results indicate that selection for an increase in bodyweight will have a positive effect on eye muscle depth, fleece weight, and reproduction traits, while selection for an increase in bodyweight will have a negative effect on fibre diameter and fibre diameter coefficient of variation.

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41

Ponzoni, R. W. "A profit equation for the definition of the breeding objective of Australian merino sheep". Journal of Animal Breeding and Genetics 103, n.º 1-5 (12 de enero de 1986): 342–57. http://dx.doi.org/10.1111/j.1439-0388.1986.tb00096.x.

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42

Sawyer, Gregory, Danielle Webster y Edward Narayan. "Measuring wool cortisol and progesterone levels in breeding maiden Australian merino sheep (Ovis aries)". PLOS ONE 14, n.º 4 (8 de abril de 2019): e0214734. http://dx.doi.org/10.1371/journal.pone.0214734.

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43

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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44

Ranilla, M. J., C. Valdés, F. J. Giráldez, M. D. Carro y S. López. "Comparative digestibility and digesta flow kinetics in two breeds of sheep". Proceedings of the British Society of Animal Science 1996 (marzo de 1996): 171. http://dx.doi.org/10.1017/s1752756200593661.

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Recent studies carried out in cattle, sheep and goats have shown differences between both species and breeds of ruminants in digestive capacity, digesta flows and fermentation rates. Most of these differences are related to their feeding behaviour and digestive physiology and could affect digestive utilization of feeds. The aim of this work was to study the digestibility and digesta kinetics in the whole digestive tract in two breeds of sheep (Churra v. Merino).Ten non-productive mature sheep (five Churra (mean LW= 44.3kgÂ±3.20) and five Merino (mean LW= 46.7kgÂ±2.22)) fitted with rumen cannulae were used in this study. Animals were fed once a day 1 kg of alfalfa hay (877 g DM/kg; 169 g CP/kg DM; 489 g NDF/kg DM).

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45

Ranilla, M. J., C. Valdés, F. J. Giráldez, M. D. Carro y S. López. "Comparative digestibility and digesta flow kinetics in two breeds of sheep". Proceedings of the British Society of Animal Science 1996 (marzo de 1996): 171. http://dx.doi.org/10.1017/s0308229600031378.

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Recent studies carried out in cattle, sheep and goats have shown differences between both species and breeds of ruminants in digestive capacity, digesta flows and fermentation rates. Most of these differences are related to their feeding behaviour and digestive physiology and could affect digestive utilization of feeds. The aim of this work was to study the digestibility and digesta kinetics in the whole digestive tract in two breeds of sheep (Churra v. Merino).Ten non-productive mature sheep (five Churra (mean LW= 44.3kgÂ±3.20) and five Merino (mean LW= 46.7kgÂ±2.22)) fitted with rumen cannulae were used in this study. Animals were fed once a day 1 kg of alfalfa hay (877 g DM/kg; 169 g CP/kg DM; 489 g NDF/kg DM).

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46

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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47

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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48

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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Benavides, M. V., S. Damak y A. P. Maher. "A putative resistant DNA marker for wool yellowing susceptibility in sheep". Genetics and Molecular Biology 23, n.º 2 (junio de 2000): 341–46. http://dx.doi.org/10.1590/s1415-47572000000200017.

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An Australian Merino flock was screened for low (resistant) and high (susceptible) yellow predictive colour (YPC) breeding values in order to compare extreme individuals using the differential display of mRNA technique. One differentially expressed cDNA band was visualised only in the resistant group. This band showed no identity with the DNA sequences of public databases; however, they showed short homologies with three database sequences related to transmembrane signalling functions. The use of these candidate genes as DNA markers needs to be confirmed against sheep with a wide range of susceptibility to wool yellowing to verify the results.

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Vallejo Adriana, Fernández Abella Daniel, Ramos Zully y Montossi Fabio. "Relationship between skin structure and wool traits for Ultrafine and Dohne Merino sheep of Uruguay". World Journal of Advanced Research and Reviews 12, n.º 1 (30 de octubre de 2021): 465–72. http://dx.doi.org/10.30574/wjarr.2021.12.1.0553.

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The demand in the world market for high quality fine and superfine wool is increasing, responding to greater wool textile industry demands and price incentives. There are few research studies focused on hair follicle population in fine and superfine Merino sheep in Uruguay. This study evaluates the association between wool follicle population and the most relevant economical wool traits. This work was carried out on Ultrafine Australian Merino (UAM) and Dohne Merino (DM) animals (lambs and rams). Phenotypic correlations between the secondary/primary follicles (S/P) and other wool traits (fiber diameter, staple length, clean fleece weight, scoured yield, coefficient of variation of fiber diameter and comfort factor parameter, were performed using histological skin cuts. Two skin samples were extracted from each lamb at two and nine months of age. These were processed at the skin histology laboratory to obtain a histological preparation for further biopsy, being able to differentiate the structures obtained to be evaluated. The results showed in the UAM group, S/P ratio in nine-month-old lambs was greater than two-month-old lambs (31.08 vs 23.12 P< 0.05). For DM group, there were no differences in the S/P ratio between age groups. Phenotypic correlations for wool characteristics obtained were of low to medium or null magnitude in both genotypes.

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