Short communication: effects of a gonadotropin application on seasonal subfertility in pigs.

In this study the reproductive performance of weaned sows in a large production unit was evaluated during periods of high (> 35 degrees C) summer temperatures. Only weaned sows of parity 2-6 (a total of n = 3386) were evaluated in two groups in 13 replicates: Group 1 (n = 1694): The sows were treated subcutaneously with 400 I.U. of Gonadotropinum sericum (pregnant mare serum gonadotropin, PMSG [eCG]) and 200 I.U. of Gonadotropinum chorionicum (human choriongonadotropin, HCG [hCG]) on the day of weaning. Group 2: (n=1692). The sows received subcutaneously 4 ml of physiological NaCl solution on the day of weaning. Weaning to service intervals, regular and irregular returns to service, farrowing rates, and subsequent litter sizes were evaluated. Control sows had longer (P < 0.01) weaning to service intervals and more (P < 0.01) regular returns to service during hot weather periods compared with the gonadotropin treated sows. Irregular returns to service were low and showed no significant differences between the treated and non-treated sows (1.4+/-0.3 % vs. 1.5+/-0.4 %). Farrowing rates and litter sizes were significantly (P < 0.01) better in the treated compared with the non-treated sows.