43 - Establishing Pregnancy Following Artificial Insemination (AI) of Angus Cows: Experience from Fort Valley State University (FVSU)

Abstract: Fixed-time artificial insemination (FTAI) provides a practical and feasible option for commercial and stud breeders to implement AI into their herds, as 100% of the herd can be inseminated at a predetermined time. FTAI can suit many herds, whether they are inseminating small numbers or the whole herd. We investigated the effects of sire and inseminator on pregnancy and birth outcomes following FTAI of Angus cows. Three Angus sires; namely GAR Quantum 7AN560, Square B True North 8052, and Tehama Tahoe B767, and two inseminators (1 and 2) were evaluated for differences in pregnancy outcomes and birth rates from 24 inseminations. Angus cows (N = 24) were synchronized with CIDR plus GnRH injection. After 7 days, CIDR was removed and each cow received 25 mg PGF2α. AI was conducted within 72 h from PGF2α injection. Cows were randomly assigned for AI between inseminators (12 cows inseminated by inseminator 1 and 12 cows by inseminator 2) and sires (6, 8, and 10 cows were inseminated by GAR Quantum, Tehama Taho, and True North semen, respectively. Pregnancy was diagnosed at 4-5 months after AI by transrectal ultrasonography. Percentage of re-cycling cows 21 days after AI was 45.8% (11/24). Pregnancy rate was 54.2% (13/24). Pregnancy rate was higher (P<0.05) for cows inseminated by inseminator 1 than by inseminator 2 (69.2% vs. 30.8%). The average age of pregnancy was 5.6 ± 0.2 months. Among sires, 46.2% (6/13) of the pregnant cows were inseminated by True North, 38.5% (5/13) by Tehama Tahoe, and 15.4% (2/13) by GAR Quantum. The pregnant cows gave birth to healthy calves at 280.8 ± 2.1 days after AI. In conclusion, both inseminator and sire affected the pregnancy rates and birth outcomes after AI in beef cattle. This study was conducted to support the establishment of a purebred Black Angus beef herd at FVSU with the application of AI.