Ilatsia E D, Migose S A, Muhuyi W B, Kahi A K
Institute of Animal Production in the Tropics and Subtropics, Department of Animal Breeding and Husbandry, Hohenheim University, Garbenstrasse 17, 70593 Stuttgart, Germany.
Trop Anim Health Prod. 2011 Dec;43(8):1575-82. doi: 10.1007/s11250-011-9845-x. Epub 2011 Apr 17.
The aim of this study was to estimate genetic and phenotypic parameters for growth and survival traits of Sahiwal cattle in Kenya and determine their relationship to milk production and fertility. Performance records of 5,681 animals were obtained from the National Sahiwal Stud and the traits considered were: birth weight (kilogrammes), weaning weight (kilogrammes), pre-weaning average daily gain (grammes per day), post-weaning average daily gain (grammes per day), yearling weight (kilogrammes), mature weight at 36 months (kilogrammes), pre-weaning survival rate (SR), post-weaning survival rate (PSR), lactation milk yield (kilogrammes), age at first calving (days), and calving interval (days). The data was analysed using univariate and bivariate animal model based on restricted maximum likelihood methods, incorporating all known pedigree relationship among animals. The additive direct effects were more pronounced than maternal genetic effects in early and in post-yearling growth performance. The additive genetic variance and heritabilities were low for SR and PSR. The correlation between direct additive genetic and maternal genetic effect were negative for pre-yearling traits. Genetic and phenotypic correlations among growth traits and between growth and milk yield were positive, whilst those between growth and fertility were weak and negative. Correlations between survival and growth were generally low and positive. The estimates obtained in this study provide the necessary technical parameters for evaluating alternative breeding programmes and selection schemes for sustainable improvement of Sahiwal cattle.
本研究的目的是估计肯尼亚萨希瓦尔牛生长和存活性状的遗传及表型参数，并确定它们与产奶量和繁殖力的关系。从国家萨希瓦尔种畜场获取了5681头动物的生产性能记录，所考虑的性状包括：出生体重（千克）、断奶体重（千克）、断奶前平均日增重（克/天）、断奶后平均日增重（克/天）、周岁体重（千克）、36月龄成熟体重（千克）、断奶前存活率（SR）、断奶后存活率（PSR）、泌乳期产奶量（千克）、初产年龄（天）以及产犊间隔（天）。基于限制最大似然法，使用单变量和双变量动物模型对数据进行了分析，纳入了动物之间所有已知的系谱关系。在周岁前和周岁后的生长性能方面，加性直接效应比母体遗传效应更为显著。SR和PSR的加性遗传方差和遗传力较低。周岁前性状的直接加性遗传效应与母体遗传效应之间的相关性为负。生长性状之间以及生长与产奶量之间的遗传和表型相关性为正，而生长与繁殖力之间的相关性较弱且为负。存活与生长之间的相关性总体较低且为正。本研究获得的估计值为评估萨希瓦尔牛可持续改良的替代育种计划和选择方案提供了必要的技术参数。
