Administering tolfenamic acid to gilts and sows before artificial insemination did not improve litter size but tended to reduce post-service serum prostaglandin F2α levels

This study examined the impact of intramuscular administration of tolfenamic acid 10 min before artificial insemination (AI) on serum PGF2α levels and reproductive performance in gilts and sows. In Experiment I, 20 gilts were divided into two groups: control (n = 10) and treatment (n = 10). Serum samples were collected 30 min before and after insemination to measure PGF2α levels. In Experiment II, 175 gilts and sows were divided into control (25 gilts and 56 sows) and treatment (16 gilts and 78 sows) groups. In both experiments, the treatment group received an intramuscular injection of 2 mg/kg tolfenamic acid 10 min before AI, while the control group received no injection. The reproductive performance of the gilts and sows was compared between the groups. In Experiment I, the serum PGF2α level in the treatment group tended to be lower after insemination compared to before AI (652.5 ± 233.9 vs. 1335.4 ± 237.9 pg/ml, respectively, P = 0.063), while no significant difference was observed in the control group (556.3 ± 206.0 vs. 653.1 ± 218.8 pg/ml, P = 0.314). Notably, gilts with serum PGF2α levels above 750 pg/ml after insemination had significantly fewer piglets born alive per litter compared to those with PGF2α levels below 750 pg/ml (5.2 ± 1.9 vs. 10.2 ± 1.2, P = 0.044). In Experiment II, no significant differences in litter traits were observed between the control and treatment groups (P > 0.05). In conclusion, administering tolfenamic acid 10 min before AI did not improve litter size at birth in either gilts or sows. However, in gilts, tolfenamic acid administration tended to reduce serum PGF2α levels. Furthermore, higher serum PGF2α levels post-insemination was associated with fewer piglets born alive per litter. This suggests that post-insemination serum PGF2α levels may affect litter size in gilts. Further research is needed to explore the factors influencing PGF2α levels after AI and to develop optimal management strategies.