Abstract #T45

# T45
Bull fertility evaluations for Angus service sires bred to Holstein cows.
J. L. Hutchison*1, P. M. VanRaden1, J. B. Cole1, G. C. Fok1, H. D. Norman2, 1Animal Genomics and Improvement Laboratory, Agricultural Research Service, USDA, Beltsville, MD, 2Council on Dairy Cattle Breeding, Bowie, MD.

The purpose of this study was to investigate the use of beef service sires bred to Holstein (HO) cows and heifers and to provide a tool for dairy producers to evaluate Angus service-sires. Many US dairy cows are now being bred to Angus sires because beef prices are high and there is a surplus of dairy heifers in many herds. Sire conception rate (SCR), a phenotypic evaluation of service-sire fertility implemented in August 2008, is based on data from the most recent 4 years, conventional-semen breedings up to 7 services, and cow parities 1 through 5. The SCR model and methodology was used in this study, with service-sire inbreeding and expected inbreeding of resulting embryo set to 0 because pedigree data were unavailable. Service-sire age was combined into 3 groups (1.8 to 4.5; 4.6 to 7.5; and >7.5 yr). A total of 97,987 breedings were available and included observations on 947 Angus service-sires and 64,061 HO cows (other beef breeds had too few records to evaluate). A mean conception rate of 30% was observed (46% standard deviation), compared with 32% for breedings with a HO cow mated to a HO sire. Publishable Angus bulls were required to have 100 total matings, 10 matings in the most recent 12 mo, and breedings in 5 or more herds. Mean SCR reliability was 56% for 95 publishable bulls, with a maximum reliability of 97% based on 8,840 breedings. Average SCR was near 0 (on an Angus base), with a range of −3.4 to 3.3. Breedings to HO heifers were also examined, which included 8,446 breedings (399 Angus service-sires and 6,570 HO heifers). A mean conception rate of 49% was observed (50% standard deviation), compared with 57% for breedings with a HO heifer mated to a HO sire. Angus sires were used more frequently for later services on problem breeders, which explains some of the difference. Mean service number was 1.77 and 2.90 for HO and Angus sires mated to HO heifers, respectively, and 2.21 and 3.41 for HO cows. Mating dairy cows to beef bulls may be profitable if the calf price is higher, fertility is better, or if practices such as sexed semen, genomic testing, and improved cow productive life allow herd owners to produce both higher quality dairy calves for replacement and beef calves for market.

Key Words: sire conception rate, beef breed