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Synchronization of Estrus in Dairy Cows with Prostaglandin F₂ and Estradiol Benzoate¹

Division of Animal and Veterinary Sciences, Box 6108, West Virginia University, Morgantown 26506-6108

ABSTRACT

A field study using 322 lactating dairy cows in seven commercial and two university herds was conducted to determine if treatment with estradiol benzoate 40 to 48 h after treatment with prostaglandin F² would enhance synchronization of estrus. Estrogen treatment tended to increase the proportion of cows in estrus within 5 d (synchronized) after prostaglandin treatment (66.9% versus 58.9%). Of synchronized cows, a greater proportion treated with estrogen (66.9%) were in estrus on d 3 than those not receiving estrogen (48.2%). First service conception rate (31.9%) and interval to second service (35.6 d) were not affected by treatment with estrogen. Milk progesterone was measured in university herds. More cows with milk progesterone concentrations 8 ng/ml were synchronized (75.4%) than those with <8 ng/ml (63.3%). Treatment with estrogen increased synchrony of cows with high progesterone (90.3%) more than prostaglandin alone (60.0%). Based on progesterone concentrations at breeding and 22 to 24 d later, estimated conception rate was 58.7%, and net conception rate based on palpation was 41.3%. Tighter synchrony of estrus can be achieved by using estradiol benzoate 40 to 48 h after prostaglandin. Concentrations of milk progesterone might predict success of treatment.

¹ Published with the approval of the Director of the West Virginia Agricultural and Forestry Experiment Station as Scientific Paper Number 1974. Supported by Northeast Regional Hatch Project 72.

² Dairy Practitioner, Herd Health and Reproduction, Shepherdstown, WV 25443.

³ Animal and Dairy Science Department, University of Vermont, Burlington 05401.

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