To determinate the effect of applying semen doses spiked with oxytocin by post-cervical insemination, on the reproductive performance of sows serviced during the months of June to October (max. registered ambient temperature of 46°C and 28 min) in northwest Mexico, 223 multi parturient sows were inseminated. Sows were assigned randomly to be serviced twice with semen from same boar(s) in 1 of 2 treatments: (1) serviced with a reduced dosage equivalent to 1.5 × 10,000,000,000 viable spermatozoa cell diluted in 40 mL of semen dose (CONT, n = 111) and (2) similar to CONT plus addition of 4 IU oxytocin to semen at service time (OXY, n = 112). Sows were serviced from June to October, using an intrauterine semen delvery device. Total number born and total number born alive were counted at farrowing. Results were compared using X² analyses. Treatment had no effect on litter size with 11.0 vs. 10.8 (P = 0.577), or on number born alive with 9.8 vs. 9.6 for CONT and OXY, respectively. OXY enhances (P = 0.03) 9.6% the farrowing rate, with means values of 84.68 vs. 93.75 for CONT and OXY, respectively. These results sugest that the addition of oxytocin to semen at serviced time improves farrowing of multi parturient sows serviced during summer-autumn in northwest Mexico, without effects on other reproductive performance variables.