ARS | Publication request: USE OF BOVINE SOMATOTROPIN IN CONJUNCTION WITH CO-SYNCH AND SELECT SYNCH PROTOCOLS FOR SYNCHRONIZING ESTRUS AND OVULATION IN BEEF COWS

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2001
Publication Date: June 1, 2001
Citation: FOSTER, H.A., WHITTIER, J.C., BURNS, P.D., BRUEMMER, J.E., BAKER, D.S., ENGLE, T.E., FIELD, T.G., WAILES, W.R., GEARY, T.W. USE OF BOVINE SOMATOTROPIN IN CONJUNCTION WITH CO-SYNCH AND SELECT SYNCH PROTOCOLS FOR SYNCHRONIZING ESTRUS AND OVULATION IN BEEF COWS. JOURNAL OF ANIMAL SCIENCE SUPPLEMENT. 2001. v. 79(Suppl. 2). p. 123.

Interpretive Summary: Objectives were to examine effects of exogenous bovine somatotropin (bST) on pregnancy rates in conjunction with two separate estrus synchronization protocols: CO-Synch and Select Synch. In the CO-Synch trial, lactating beef cows (n=690) from 3 locations were administered 100 mcg of GnRH on d 0 and 9, PGF (25 mg) on d 7 and artificially inseminated (AI) on d 9. Cows were assigned to the following treatments: 500 mg of bST on d 0(Trt 1), d 7 (Trt 2), d 9 (Trt 3), and no bST (Control). Pregnancy rates for treatments 1,2,3 and Control were 30.0, 26.9, 33.1, and 27.1%, respectively, and did not differ (P>0.05). Thus, bST had no effect on pregnancy results in the CO-Synch estrous synchronization protocol. In the second trial, lactating beef cows (n=581) were synchronized using the Select Synch protocol. On d 0, cows received 100 mcg of GnRH, followed 7 d later by 25 mg of PGF, combined with heat detection and AI on d 6-11. Cows were assigned to the following treatments: 500 mg of bST on d 0 (Trt 1), d 7 (Trt 2), and no bST (Control). Estrus response rates were higher for Trt 1 (69.84 +/- 4.9; P<0.05), but there were no differences for estrous response rates between Trt 2 (58.4 +/- 4.9) and 3 (58.9 +/- 4.9; P>0.05). Conception rates were higher (P<0.05) for cows in Trt 1 (64.1%) than for cows in Trt 2 (35.5%). However, conception rates for Trt 1 cows were not higher than Control (60.2%, P>0.05). Based on this trial, bST does not have a beneficial effect on conception rates, but does have a deleterious effect when administered at the time of PGF.

Technical Abstract: Objectives were to examine effects of exogenous bovine somatotropin (bST) on pregnancy rates in conjunction with two separate estrus synchronization protocols: CO-Synch and Select Synch. In the CO-Synch trial, lactating beef cows (n=690) from 3 locations were administered 100 mcg of GnRH on d 0 and 9, PGF (25 mg) on d 7 and artificially inseminated (AI) on d 9. Cows were assigned to the following treatments: 500 mg of bST on d 0(Trt 1), d 7 (Trt 2), d 9 (Trt 3), and no bST (Control). Pregnancy rates for treatments 1,2,3 and Control were 30.0, 26.9, 33.1, and 27.1%, respectively, and did not differ (P>0.05). Thus, bST had no effect on pregnancy results in the CO-Synch estrous synchronization protocol. In the second trial, lactating beef cows (n=581) were synchronized using the Select Synch protocol. On d 0, cows received 100 mcg of GnRH, followed 7 d later by 25 mg of PGF, combined with heat detection and AI on d 6-11. Cows were assigned to the following treatments: 500 mg of bST on d 0 (Trt 1), d 7 (Trt 2), and no bST (Control). Estrus response rates were higher for Trt 1 (69.84 +/- 4.9; P<0.05), but there were no differences for estrous response rates between Trt 2 (58.4 +/- 4.9) and 3 (58.9 +/- 4.9; P>0.05). Conception rates were higher (P<0.05) for cows in Trt 1 (64.1%) than for cows in Trt 2 (35.5%). However, conception rates for Trt 1 cows were not higher than Control (60.2%, P>0.05). Based on this trial, bST does not have a beneficial effect on conception rates, but does have a deleterious effect when administered at the time of PGF.