POTENTIAL BENEFITS OF BOVINE EMBRYO-MANIPULATION TECHNOLOGIES TO GENETIC-IMPROVEMENT PROGRAMS

Embryo transfer has become the most powerful tool animal breeders have acquired since artificial insemination. Several countries, including Canada, have incorporated multiple ovulation and embryo transfer (MOET) into progeny testing programs to bolster genetic improvement in dairy or beef cattle. The Canadian ''TEAM'' project produced 55 complete full-sib families with projected generation intervals for sib-tested bulls 19% shorter than current progeny tests for dairy bulls. Computer simulations of such schemes predict rates of genetic improvement 8 to 9.5% higher than from current progeny test programs. With selection of juvenile as well as adult males and females as breeding stock, a 12% advantage is predicted. However, when NF is also utilized to harvest embryos from 1 to 5 mo old calves, a 22% increase in rates of genetic improvement is predicted. The merits of centralized versus dispersed schemes and open versus closed schemes are compared. Satellite nucleus schemes are proposed as more optimal structures of MOET schemes. Risks associated with the use of sib-tested bulls are also discussed.