Rosales Nieto C A, Ferguson M B, Thompson H, Briegel J R, Macleay C A, Martin G B, Thompson A N
CRC for Sheep Industry Innovation and the University of New England, Armidale, NSW, Australia.
Department of Agriculture and Food of Western Australia, South Perth, WA, Australia.
Reprod Domest Anim. 2015 Aug;50(4):637-42. doi: 10.1111/rda.12542. Epub 2015 May 19.
Greater depths of muscle are associated with better reproductive performance in ewe lambs, but, in adult ewes, reproductive performance also seems to vary with liveweight gain during the mating period. Therefore, in a large field study with Merino ewe lambs, we tested whether the relationships among eye muscle depth (EMD), fat depth (FAT) and reproductive performance depend on liveweight gain during the mating period. We selected lambs with a wide range in phenotypic values for depths of eye muscle (EMD) and fat (FAT) and assigned them to dietary treatments designed to achieve low (LOW, n = 244) or high (HIGH, n = 237) rates of liveweight gain during a 28-day mating period. The LOW treatment maintained live weight, whereas the HIGH treatment gained 179 ± 3.8 g/day (p < 0.001). From those ewe lambs that attained puberty, first oestrus was detected at live weight 37.8 ± 0.2 kg and age 232 days. The proportion of ewes that attained puberty increased with EMD (p < 0.01). Ewes from the HIGH treatment were more fertile (pregnant ewes per 100 ewes exposed to rams) and had a higher reproductive rate (foetuses in utero per 100 ewes exposed to rams; p < 0.001) than those from the LOW treatment. Fertility and reproductive rate were positively correlated with weight gain during mating as well as live weight at the start of mating, FAT and EMD (p < 0.05 to <0.001). We conclude that faster growth, due to either extra nutrition during mating or higher phenotypic potential for fat and muscle, will increase reproductive performance in ewe lambs mated at 8 months of age.
母羊羔肌肉深度更深与繁殖性能更好相关，但在成年母羊中，繁殖性能似乎也随交配期体重增加而变化。因此，在一项针对美利奴母羊羔的大型田间研究中，我们测试了眼肌深度（EMD）、脂肪深度（FAT）与繁殖性能之间的关系是否取决于交配期的体重增加。我们选择了眼肌深度（EMD）和脂肪（FAT）表型值范围广泛的羔羊，并将它们分配到旨在在28天交配期内实现低（LOW，n = 244）或高（HIGH，n = 237）体重增加率的饮食处理组。LOW处理组维持体重，而HIGH处理组每天增重179 ± 3.8克（p < 0.001）。在那些达到青春期的母羊羔中，首次发情在体重37.8 ± 0.2千克、年龄232天时被检测到。达到青春期的母羊比例随EMD增加（p < 0.01）。与LOW处理组相比，HIGH处理组的母羊更易受孕（每100只接触公羊的母羊中怀孕的母羊数）且繁殖率更高（每100只接触公羊的母羊子宫内的胎儿数；p < 0.001）。受孕率和繁殖率与交配期体重增加以及交配开始时的体重、FAT和EMD呈正相关（p < 0.05至<0.001）。我们得出结论，由于交配期额外的营养或更高的脂肪和肌肉表型潜力导致的更快生长，将提高8月龄配种的母羊羔的繁殖性能。
