Injecting postpartal gilts or sows with a supraphysiological dose of oxytocin: effects on sow and piglet performances

The goal of this project was to determine the effects of a supraphysiological dose of oxytocin given to gilts or multiparous sows 8 to 12 h after the end of farrowing on the performance of their progeny. Sows from three parity groups (1 = parity 1; 2 = parities 2, 3, and 4; 3 = parities 5 to 14) received no injection (CTL, controls; n = 17, 27, and 23 for parity groups 1, 2, and 3, respectively) or one intramuscular injection of 75 IU of oxytocin (OXY, n = 17, 24, and 26 for parity groups 1, 2, and 3, respectively) 8 to 12 h after birth of the last piglet. Colostrum samples were obtained 8 h after oxytocin injection in 18 sows from parity group 2 (CTL, n = 10; OXY, n = 8). Standard milk composition was measured as well as the Na/K ratio, and IGF-1, IgG, and IgA concentrations. The same sows were used to obtain blood samples from four male piglets of average litter body weight (BW) 8 h post-treatment to measure concentrations of IGF-1, IgG, and IgA. Piglets and sows were weighed at farrowing and weaning (day 21) and sow feed intake and piglet mortality were recorded. There was no effect of OXY on sow or piglet BW at any measured times and percent preweaning piglet mortality was not affected by OXY or parity. First-parity sows had lower BW than multiparous sows at both times (P < 0.001), and piglet average daily gain from birth to weaning was greater in parity group 2 compared with first-parity litters (P < 0.05). Average daily sow feed intake over the first week of lactation tended to be greater in OXY vs CTL sows (P = 0.07), and multiparous sows consumed more feed than first-parity sows on all weeks of lactation (P < 0.001). Eight hours after treatment, there was a tendency for colostral Na to be greater in OXY vs CTL sows (P = 0.06), and none of the measured variables in piglet blood were affected by treatment. In conclusion, injecting 75 IU of oxytocin 8 to 12 h after the birth of the last piglet did not prolong the period of colostrogenesis or improve the growth or survival of piglets and this was consistent across parities.