Stochastic modeling of multiple ovulation and embryo transfer breeding schemes in small closed dairy cattle populations.

Genetic changes and genetic drift in three small closed dairy cattle populations were examined with a stochastic simulation model. Multiple ovulation and embryo transfer and AI techniques were simulated in three populations, two with 88 breeding females each and one with 352 breeding females. The selection goal was to maximize genetic improvement in milk yield. The reduction in genetic variation due to inbreeding and linkage disequilibrium was accounted for in the simulation. Strict restriction against inbred mating slowed genetic progress significantly in the small population but would not be consequential in the larger population. However, allowing inbred mating in the smaller population caused a rapid accumulation of inbreeding. Linkage disequilibrium was as important as inbreeding in reducing genetic variation. Genetic drift variance was much smaller in the larger population.