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Prostaglandin F₂ for Lactating Dairy Cows with a Palpable Corpus Luteum but Unobserved Estrus^1,2,3,

Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506

ABSTRACT

Two experiments in 17 dairy herds were for the effectiveness of prostaglandin F₂ (treatment) in inducing luteolysis and reducing intervals to conception of 308 cycling lactating dairy cows. Cows with unobserved estrus before first insemination (Experiment 1) and non-pregnant cows with unobserved estrus after insemination (Experiment 2) were eligible for treatment. Cows in Experiment 1 were assigned alternately either to an untreated control group of 85 or to a group of 138 that received 25 mg prostaglandin F₂ after detection of a corpus luteum by ovarian palpation. Cows were inseminated either at estrus or at 72 and 96 h posttreatment in the absence of detected estrus. Intervals from treatment to estrus, to first service, and to conception were longer for controls than for treated cows. Conception at first service was similar for controls (39%) and for treated (43%) cows. Procedures were similar for Experiment 2. Intervals from treatment to estrus and treatment to first service were longer for control cows, and treatment to conception tended to be longer for 39 controls than for 46 treated cows. Conception at first service was similar for controls (52%) and treated (44%) cows. Prostaglandin F₂ was 91% effective for inducing luteolysis based on progesterone concentrations in blood serum. Successful treatment was dependent upon accurate diagnosis of a functional corpus luteum. Days from treatment to conception were reduced for cows with unobserved estrus if treated cows were inseminated at estrus or by appointment in the absence of detected estrus.

¹ Contribution No. 83-165-J, Kansas Agricultural Experiment Station, Manhattan 66506.

² This research was part of regional research project NC-113, "Methods for Improvement of Fertility in Cows Postpartum."

³ Prostaglandin F₂, (Lutalyse®) and partial financial support were donated kindly by The Upjohn Company, Kalamazoo, MI 49001. The authors also wish to thank the Kansas dairymen who cooperated in this project and express special appreciation to M. K. Schmidt and M. Jamshedi for their assistance at the Kansas State University Dairy Research and Teaching Center.

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