Improved synchrony, conception rate, and fecundity in postpartum suckled beef cows fed melengestrol acetate prior to prostaglandin F2 alpha.

Occurrence of estrus, conception rate, and fecundity were compared between postpartum suckled beef cows fed or not fed melengestrol acetate (MGA) before synchronizing estrus with prostaglandin F2 alpha (PG). One hundred thirty-three purebred Angus cows were stratified by age and days postpartum to one of two treatments. All cows received an injection containing 25 mg of PG; however, one group (MGA+PG) was fed .5 mg of MGA.cow-1.d-1 for 14 d then received PG 17 d after the last feeding of MGA. The other group (PG) received only PG. Cows in both treatments that failed to exhibit estrus within 6 d after PG received a second injection of PG 11 d after the first injection was administered. Cows were checked for estrus from the first PG injection until 6 d after the second PG injection. Cows were inseminated with semen from a 3/4 Brahman bull 12 h after observed estrus. Cows were exposed to Angus bulls after the AI period. Conception date was determined by palpation per rectum and verified by calving date and calf phenotype. Differences in response variables were analyzed by chi-square. A greater proportion of cows (P < .04) that were pretreated with MGA exhibited estrus after the first injection of PG (76%) than of cows that received only PG (60%). Total response did not differ between treatments after both injections of PG. Conception rate among cows that received a first service was higher (P < .007) for the MGA+PG (88%) group than for the PG (67%) group, although the total number of cows that received a first service was not different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of B-mode, linear array ultrasonography for evaluating the technique of bovine artificial insemination.

B-Mode, linear array ultrasonography was used to evaluate the site of semen deposition in live cows. The insemination sheath was modified to hold a brass bead that was deposited at the simulated site of semen deposition. The position of the bead was identified by ultrasonography and the bead was recovered by pulling a nylon line that was attached to the bead. An ultrasound technician identified placement of the bead in the site designated for semen deposition by a skilled inseminator in 24 of 25 cases. This procedure improves methods for inseminator training by providing a method of evaluating insemination technique using live animals rather than excised reproductive tracts. The ultrasound equipment used for inseminator evaluation is affordable, portable, and does not pose a human health risk.