Genetic Change in a Nucleus Breeding Dairy Herd Using Embryo Transfer

Abstract

The genetic change by selecting for milk production in a nucleus breeding dairy herd using multiple ovulation and embryo transfer (MOET) was studied by computer simulation of an adult MOET scheme. The size of the herd was chosen to be small, 256 progeny per generation (3.7 years), to study the effect of finite population size on the genetic response. Alternative systems, with different number of sires and with use of progeny test information, were considered. The genetic response in milk production simulated was from 1.0 to 1.26% per year for the different alternative systems. This was substantially less than the 1.78 to 2.24% per year predicted theoretically from adult MOET schemes. The accuracy of evalution was increased when the progeny test of sires was used in estimating breeding values but this had little effect on the response. The correlated genetic change in fertility from selection on milk production was also simulated. With the unfavourable genetic correlation used (r _G=-0.2) fertility decreased slightly genetically as milk yield increased genetically.

Key Words:

• MOET
• population size
• population size
• reduced animal model