Abstract

The objectives of the present series of experiments were to develop a timed artificial insemination (TAI) program for dairy heifers and to utilize a TAI program to evaluate the effect of flunixin meglumine (Banamine^®; Schering-Plough Animal Health Corp., Atlanta, GA, USA), a prostaglandin H synthase (PGHS)-2 inhibitor, on pregnancy rate and embryo survival. In Experiment 1, 247 heifers were assigned randomly to a prostaglandin F (PGF)/gonadotropin-releasing hormone (GnRH) TAI [i.e., 2 injections of Lutalyse^® (25 mg, IM; Pfizer Animal Health Inc., Groton, CT, USA) given 14 days apart in the PM; 60 h after the 2nd Lutalyse injection, heifers received a GnRH injection (Cystorelin^®; 100 µg, IM; Merial, Duluth, GA, USA) and were TAI] or a 5-day CIDR/Synch TAI [intravaginal insertion of a CIDR^® device (Pfizer Animal Health Inc.) and an injection of GnRH in the AM; 5 days later in the AM, the CIDR insert was removed and Lutalyse was injected, followed by a 2nd injection of Lutalyse^® 12 h later; heifers were TAI and injected with GnRH at 72 h after CIDR removal]. Blood samples for progesterone analyses were taken 7 days apart prior to initial PGF or CIDR insertion from the respective groups to determine cycling status. The CIDR/Synch TAI heifers tended to have greater Day 32 (53.1, >46.2%) ultrasound pregnancy rate (USPR) and Day 42 (50.8, >43.7%) rectal palpation (RPPR) than PGF/GnRH heifers (P = 0.10); 4/9 non-cycling heifers of the CIDR/Synch TAI group conceived v. 0/3 of the PGF/GnRH TAI group. In Experiment 2, 176 heifers underwent the CIDR/Synch TAI protocol. However, 2 injections of cloprostenol [500 µg AM/PM; Estrumate^®, Schering-Plough Animal Health Corp.) were used to regress the CL at CIDR removal. Heifers at initiation of the CIDR/Synch TAI protocol were assigned randomly to receive injections of Banamine (400 mg IM) at Day 15.5 and at Day 16.0 or no injections (control). Banamine treatment failed to alter either Day 32 USPR (59.6% Banamine v. 59.8% control) or Day 46 RPPR (59.6% Banamine v. 58.6% control). Overall, 4/11 non-cycling heifers conceived. In Experiment 3, 147 heifers underwent a UsedCIDR/Synch TAI protocol utilizing cloprostenol as in Experiment 2. A 5-day used CIDR was employed. Heifers at initiation of the UsedCIDR/Synch TAI protocol were assigned randomly to receive injections of Banamine (400 mg IM) at Day 15.5 and at Day 16.0 or no injections (control). Banamine treatment failed to alter either Day 32 USPR (60.5% Banamine v. 62.0% control) or Day 46 RPPR (59.2% Banamine v. 60.6% control). Pooled overall analyses of pregnancy rates for dairy heifers receiving the CIDR/Synch TAI treatments (n = 451), adjusted for experiments, were 58.3% at Day 32 (USPR) and 57.6% at Day 46 (RPPR). In conclusion, Banamine failed to improve pregnancy rate and/or late embryo survival in dairy heifers, and a CIDR/Synch TAI program is very effective for optimizing the pregnancy rate in dairy heifers.