Pregnancy rates and serum 13,14-dihydro-15-keto-PGF2α concentrations in recipient Nelore heifers treated with meloxicam after the transfer of in vitro-produced embryos

This study aimed to determine if the administration of meloxicam, a cyclooxygenase 2 inhibitor, to Nelore (Bos taurus indicus) heifers, in which embryo transfer is more difficult and requires a greater manipulation of the reproductive tract than in Bos taurus females, would improve the pregnancy rates by decreasing serum PGFM concentrations. After estrous synchronization, multiparous recipient heifers (n = 85) were selected as embryo recipients and were randomly allocated into two groups: CON (n = 42), the control group, in which animals received 10 mL of saline intramuscularly (the same volume of meloxicam), and MEL (n = 43), the group in which animals were treated with meloxicam. According to the degree of passing the catheter, recipients from both groups were classified as grade I (easy; <80 seconds) and grade II (difficult; >80 seconds). One hour before embryo transfer, MEL recipients received an injection of 200 mg of meloxicam. Blood samples were collected from all heifers 1 hour before embryo transfer and 4 and 8 hours after embryo transfer to determine the serum concentrations of 13,14-dihydro-15-keto-PGF2α (PGFM), a PGF2α metabolite. A significant difference in the pregnancy rates on Day 30 was observed in MEL animals between those classified as grade I and II (90.48% vs. 54.54%, respectively; P < 0.01). Considering the animals from CON, the pregnancy rates were similar between grades I and II. Serum concentrations of PGFM from samples collected 4 and 8 hours after embryo transfer were lower in pregnant animals from MEL grade I than in pregnant animals from MEL grade II. Considering the pregnant females from CON, no difference was observed from samples collected 4 and 8 hours after embryo transfer. Interestingly, no difference in PGFM serum concentrations was observed between the pregnant females from MEL grade II and pregnant females from CON (P < 0.05). Thus, we conclude that meloxicam had a positive effect on the pregnancy rates of grade I Nelore heifers.