Zonabend König E, Strandberg E, Ojango J M K, Mirkena T, Okeyo A M, Philipsson J
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
International Livestock Research Institute, Nairobi, Kenya.
J Anim Breed Genet. 2017 Dec;134(6):531-544. doi: 10.1111/jbg.12260. Epub 2017 Mar 27.
The aim of this article was to study opportunities for improvement of the indigenous and threatened Red Maasai sheep (RM) in Kenya, by comparing purebreeding with crossbreeding with Dorper sheep (D) as a terminal breed, in two different environments (Env. A and a harsher Env. B), assuming different levels of genotype-by-environment interaction (G × E). Breeding goals differed between environments and breeds. Four scenarios of nucleus breeding schemes were stochastically simulated, with the nucleus in Env. A. Overall, results showed an increase in carcass weight produced per ewe by more than 10% over 15 years. Genetic gain in carcass weight was 0.17 genetic SD/year (0.2 kg/year) across scenarios for RM in the less harsh Env. A. For survival and milk yield, the gain was lower (0.04-0.05 genetic SD/year). With stronger G × E, the gain in the commercial tier for RM in the harsher Env. B became increasingly lower. Selection of females also within the commercial tier gave slightly higher genetic gain. The scenario with purebreeding of RM and a subnucleus in Env. B gave the highest total income and quantity of meat. However, quantity of meat in Env. A increased slightly from having crossbreeding with D, whereas that in Env. B decreased. A simple and well-designed nucleus breeding programme would increase the genetic potential of RM. Crossbreeding of RM with D is not recommended for harsh environmental conditions due to the large breed differences expected in that environment.
本文旨在通过比较纯种繁育和与杜泊羊（D）杂交（杜泊羊作为终端品种）在两种不同环境（环境A和更恶劣的环境B）下的情况，研究肯尼亚本土濒危的红马赛羊（RM）的改良机会，假设存在不同水平的基因型与环境互作（G×E）。不同环境和品种的育种目标有所不同。随机模拟了四种核心育种方案，核心群位于环境A。总体而言，结果表明，在15年的时间里，每只母羊的胴体重量增加了10%以上。在较温和的环境A中，RM各方案的胴体重量遗传进展为每年0.17遗传标准差（0.2千克/年）。对于存活率和产奶量，遗传进展较低（每年0.04 - 0.05遗传标准差）。随着G×E效应增强，在更恶劣的环境B中，RM商品代的遗传进展越来越低。在商品代中选择母羊也能带来略高的遗传进展。RM纯种繁育且在环境B中有一个子核心群的方案带来了最高的总收入和肉类产量。然而，环境A中的肉类产量因与杜泊羊杂交而略有增加，而环境B中的肉类产量则有所下降。一个简单且设计良好的核心育种计划将提高RM的遗传潜力。由于在恶劣环境条件下预期品种差异较大不建议RM与杜泊羊杂交。
