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ARS Home » Southeast Area » Booneville, Arkansas » Dale Bumpers Small Farms Research Center » Research » Publications at this Location » Publication #144801


item FLORES, R
item Looper, Michael
item THOMAS, M

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2003
Publication Date: 4/1/2004
Citation: Flores, R., Looper, M.L., Thomas, M.G., Hallford, D.M. 2004. Influence of bovine somatotropin on estrous characteristics and reproduction of holstein cows during summer months. Professional Animal Scientist. 20:191.

Interpretive Summary: Treatment of cattle with bovine somatotropin (bST) to increase milk yields is becoming a common management practice; however, bST treatment may reduce reproductive performance. Reproductive behavior and performance of postpartum Holstein cows treated with and without bST were studied. Treatment of cows with bST decreased the number of days to first service but did not influence first service conception rates or pregnancy rates, suggesting that bST did not adversely affect reproductive performance. This information is of interest to extension personnel and agricultural professionals who advise cattle producers on reproductive management.

Technical Abstract: A field trial was conducted to evaluate the effects of bovine somatotropin (bST) on estrous characteristics of multiparous, lactating Holstein cows (n = 44) during the summer months. Cows were randomly assigned to receive bST (500 mg, sc, every 14 d) or no bST (control) and fitted with a HeatWatch® transmitter to record estrous activity. A temperature-humidity index (THI) was calculated for the day of estrous onset. Duration of estrus, number of standing events and quiescent periods between standing events were similar (P > 0.10) between bST and control cows. Duration of estrus was not influenced (P > 0.10) by THI. However, number of standing events was influenced (P < 0.05) by THI and averaged 20.3 ± 3.0, 8.6 ± 1.3, and 8.9 ± 1.2 for THI 1, THI 2, and THI 3, respectively. Quiescent periods observed between standing events tended (P = 0.11) to be influenced by THI and were 1.2 ± 0.8, 3.0 ± 0.4 and 3.0 ± 0.4 h for THI 1, THI 2, and THI 3, respectively. Days to first service were less (P = 0.07) for bST-treated cows than for control cows. First service conception rates and pregnancy rates were not influenced (P > 0.10) by bST. Pregnancy rates tended (P = 0.13) to be reduced when THI was above 72. Although pregnancy rates of lactating dairy cows were not influenced by bST during the summer, characteristics of behavioral estrus were reduced and pregnancy rates tended to decrease as ambient temperature and humidity increased.