Abstract
The objective was to compare reproductive performance of Angus-cross beef cows synchronized with GnRH, a progesterone-based intravaginal insert (Controlled Internal Drug Release, CIDR) for 5-d, and one dose of either dinoprost (PGF) or cloprostenol (CLP, a PGF analogue) or two doses of PGF on the day of CIDR withdrawal. All cows (N=830) at six locations received 100μg of GnRH and a CIDR on Day 0. Within farm, cows were randomly allocated to receive 25mg of PGF at the time of CIDR insert removal on Day 5 (1×PGF; N=277), two 25mg doses of PGF, the first given on Day 5 at the time of CIDR removal and the second 7h later (2×PGF; N=282), or 500μg of CLP at the time of CIDR removal on Day 5 (1×CLP; N=271). All cows were given 100μg of GnRH on Day 8 (72h after CIDR removal) and concurrently inseminated (5-d CO-Synch+CIDR). Cows were fitted with a pressure-sensitive estrus detection device at the time of CIDR withdrawal. Timed-AI pregnancy rates were greater (P<0.0001) in the 2×PGF (69.0%) than the 1×PGF (52.0%) and 1×CLP (54.3%) treatments. However, breeding-season pregnancy rates were not different among treatments (87.0% for 1×PGF, 92.9% for 2×PGF and 87.5% for 1×CLP; P>0.1). In conclusion, cows that received two doses of PGF on the day of CIDR removal in a 5-d CO-Synch+CIDR synchronization protocol had excellent timed-AI pregnancy rates that were greater than in cows receiving a single treatment with either PGF or CLP.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call