Influence of Seminal Additives on Sow Fertility

The objective of this study was to determine the effect of 4 different seminal additives on pregnancy and farrowing rates and litter size in primiparous and multiparous sows. The study was performed on a commercial facility in Spain during a 12-month period. A total of 1091 sows were randomly allotted by parity to receive one of four additives in seminal plasma or served as controls: 1) 87 µg of cloprostenol (Planate®, Schering-Plough Animal Health; n = 158), 2) 5 IU oxytocin (Ovivex®, S.P.Veterinaria; n = 154), 3) 0.2 µg buserelin acetate (Receptal®, Merck; n = 93), 4) 5 IU oxytocin + 0.2 µg buserelin acetate (n = 81), and 5) control (n = 605). Additives were added to the semen dose 15 min prior to insemination. Sows had daily boar contact for 15 d after weaning for estrus detection. Sows were artificially inseminated at detection of estrus and at 24 h intervals if still exhibiting estrus. Additives were administered only during first insemination. Pregnancy rates were assessed by real-time ultrasonography on d 28. Pregnancy and farrowing rates were analyzed by logistic regression using a generalized linear mixed model that included treatment as fixed effect, group as random effect and parity as covariate. Litter size was analyzed by ANOVA using a linear mixed model that included the same effects and covariates as above. Multiple comparisons were accounted for with Tukey adjustment. Pregnancy and farrowing rates did not differ between groups (P = 0.3 and 0.1, respectively). Total born and born alive litter sizes increased in response to all seminal additives compared to control (P < 0.0001). We conclude that addition of seminal plasma additives at first breeding will increase litter size in both primiparous and multiparous sows.