Monte Carlo Simulation to Assess the Impact of Adult MOET Schemes in Somba Cattle

Abstract

Monte Carlo simulations were carried out in order to assess the impact of multiple ovulation and embryo transfer (MOET) on the dairy performance of Somba cattle. Adult MOET-nucleus schemes were simulated over 20 generations of selection, assuming a fixed test capacity of 512 milk recorded females, a success rate of transfer of 70%, a survival rate of 70% and various sibship sizes (n_D = 4, 8, 16). Selection criteria were the BLUP estimates of the true additive genetic values of candidates using the reduced animal model. For different combinations of number of donors (D = 64, 128, 256) and number of sires (S = 4, 8, 16) to be selected, the simulated genetic response in milk yield ranged from 0.088 to 0.127 phenotypic standard deviation units (SU) per year. These figures corresponded to a genetic progress of 2.2 to 3.2% of the population mean per year (coefficient of variation in milk yield is 25% for Somba cattle). For all alternatives with regard to population structure, the simulated rate of inbreeding ranged from 1.32 to 2.93% per year, while the expected one ranged from 0.83 to 3.32%. Compared to the rate of inbreeding commonly admitted in a conventional progeny-testing scheme (0.1 to 0.2% per year), the rates of inbreeding expected from the simulated adult MOET schemes were quite high and could be a cause of concern. Strategies to reduce inbreeding in short or medium terms were examined.