|Van Vleck, Lloyd|
Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: 8/21/1997
Publication Date: N/A
Interpretive Summary: Several biotechnological tools are available to use to improve genetic gains from selection in dairy cattle. This study used deterministic modeling of dairy cattle nucleus herds to assess the value of multiple evaluation and embryo transfer (MOET), in vitro embryo production (IVEP) and sexing of semen (SS) in comparison to progeny testing with artificial insemination (PTAI). Sexing of semen was found to have minor effects on selection responses (about 1%) but would reduce the number of embryo transfers needed per year for equivalent genetic gain. Optimum MOET-IVEP breeding programs could be competitive with efficient PTAI programs. Rates of inbreeding would be greater with MOET-IVEP than PTAI. The variability of response would also be greater with MOET-IVEP than with PTAI due to the relatively small number of cows (583 to 3000) in a MOET-IVEP herd.
Technical Abstract: Deterministic modeling of dairy cattle nucleus herds using multiple ovulation, embryo transfer (MOET), in vitro embryo production (IVEP) and sexed semen was used to compare 15-year selection responses with an effici- ent progeny testing system (PT). Selection response adjusted for inbreed- ing depression (RFy) in adult and juvenile nucleus herds using MOET-IVEP, was optimized for several population structures and sizes. High responses are possible in juvenile or adult MOET-IVEP nucleus of 1,000 or more first- lactation cows, with 64 or 128 progeny per donor female. These responses are competitive with an efficient PT scheme for RFy. Adult nucleus herds of 655 to 2300 first-lactation cows could have rates of RFy similar to PT. Juvenile nucleus herds had lower responses than adult nucleus herds with population sizes of 1,000 or less and slightly greater responses compared to adult with population sizes of 4,000 or more, and inbreeding rates were higher. Sexed semen had minor effects on responses (0.4 to 1.4%), but allowed a reduction in the total number of embryo transfers per year for the same rate of genetic gain. Optimum MOET-IVEP schemes will be competi- tive with PT for RFy, but inbreeding rates and variability of response will be higher. Effect of semen sexing on RFy will be comparatively small.