The effect of short term calf removal in combination with GnRH treatment and the effect of limited nursing on reproductive performance of postpartum suckled beef cows administered PGF 2α for ovulation control

Abstract

Over a two year period, postpartum suckled Hereford and Angus Cows (n=213) were administered two injections of PGF 2α (25 mg/injection) and divided into three groups. No additional treatments were administered to cows in Group I and calves were allowed to nurse their dams ad libitum. In Group II, calves were removed for 48 hours beginning on the third day following the initial PGF 2α injection. These cows were given a subcutaneous injection of 250 μg GnRH dissolved in 2% carboxymethylcellulose midway through the 48 hour period. In Group III, calves were allowed to nurse their dams for only one hour per day for the first 7 days after the initial PGF 2α injection. In year 1, PGF 2α was administered 14 days apart whereas in year 2, PGF 2α was administered 11 days apart. Cows were artificially inseminated at 72 and 96 hours after the second injection of PGF 2α. In year 1, the numbers of cows that conceived to the timed inseminations were similar (P > .10) for the three groups. In year 2, a higher percentage of cows in groups II (P < .10) and III (P < .05) conceived to the timed inseminations than in group I. Other reproductive performance parameters were similar (P > .10) between groups for both years 1 and 2. In summary, limited nursing and short term calf removal in conjunction with GnRH treatment may improve the pregnancy rate in cows administered PGF 2α for ovulation control.