Prostaglandin F2 alpha for lactating dairy cows with a palpable corpus luteum but unobserved estrus

Abstract

Two experiments in 17 dairy herds were for the effectiveness of prostaglandin F2 alpha (treatment) in reducing luteolysis and inducing intervals to conception of 308 cycling lactating dairy cows. Cows with unobserved estrus before first insemination (Experiment 1) and nonpregnant 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 alpha 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 controls (52%) and treated (44%) cows. Prostaglandin F2 alpha 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.