Genetic evaluation of breeding strategies for improvement of dairy cattle in Kenya

摘要

A deterministic approach was used to compare breeding strategies utilizing local and imported semen for improvement of dairy cattle in Kenya. The local selection programs considered were a closed progeny testing scheme (CPT) and a young bull system progeny of local bulls (PLB). The continuous semen importation (CSI) and young bull system progeny of imported bulls (PIB) were the strategies based on imports. The breeding strategies were compared on the basis of selection response. The effect of genetic correlation (r g) and initial differences in genetic merit between the two populations was also examined. The CSI and PIB strategies ranked above CPT by, correspondingly, 35.1% and 25.0% when the r g between Kenya and the USA was assumed to be one. At a r g of 0.58, imports from countries which are 1.50 standard deviation (SD) above the local population were superior to CPT but equal to PLB. This means that if CSI is to be used at a r g of 0.58, then only semen from countries which are >1.50SD should be imported. At a r g of 0.70 and with an initial genetic difference of 1.25SD, the economic responses in CSI and PLB were equal. This indicates that semen importation is only justified when genotype-environment interaction is >0.70. It is concluded that wholesale importation of semen as a means of achieving sustainable genetic progress in Kenya is a less optimal solution and there is the need for an effective local selection program.