Association between the incidence of stillbirths and expulsion interval, piglet birth weight, litter size and carbetocin administration in hyper-prolific sows

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In commercial swine herds in Thailand, the incidence of stillbirths averages 7.3% and varies from 5.1 to 8.2% between herds. Over the last decade, the incidence of stillbirths has tended to increase due to higher number of piglets born per litter through genetic selection. The present study investigated the influence of piglets’ expulsion interval, umbilical cord intactness, birth weight, litter size at birth and carbetocin administration during the mid-period of parturition on the incidence of stillborn piglets in hyper-prolific sows. In total, 1225 live-born and 103 stillborn piglets from 80 Danish Landrace × Yorkshire crossbred sows were investigated. The physiological characteristics of the newborn piglets were compared between live-born and stillborn piglets. Piglet body weight was determined within 5 min of birth. The sows were classified into two groups according to the pharmacological intervention during the farrowing process: i) NATURAL (n = 62): sows farrowed naturally; and ii) CARBETOCIN (n = 18): the uterine contraction was induced after the 7th piglet was born using carbetocin. On average, the total number of piglets born per litter and number of piglets born alive per litter were 17.5 ± 3.8 and 15.3 ± 3.7, respectively. The incidence of a stillborn piglet was 7.4% (103/1402 piglets). Of all the sows, 41.3, 27.5, 18.8 and 12.6% had 0, 1, 2 and ≥ 3 stillborn piglets per litter, respectively. The variables that differed between live-born and stillborn piglets included the expulsion interval (13.9 vs. 33.0 min, P = 0.002), piglet body weight at birth (1175 vs. 1002 g, P < 0.001), total number of piglets born per litter (18.2 vs. 20.0, P < 0.001), broken umbilical cord (24.1 vs. 46.8%, P<0.001) and meconium staining score (1.20 vs. 1.41, P = 0.005). The farrowing duration of sows without any stillborn piglets was shorter than sows with ≥ 3 stillborn piglets per litter (221 ± 32.0 min vs.373 ± 65.0 min, respectively, P = 0.039). The use of carbetocin during parturition reduced the farrowing duration from 365 to 212 min (153 min, P< 0.01), without affecting the number of stillborn piglets per litter (P> 0.05). In conclusion, a prolonged expulsion interval, broken umbilical cord and low piglet birth weight are significant risk factors for stillborn piglets. The administration of 0.4 µg/kg of carbetocin during the mid-period of parturition reduced the farrowing duration, without affecting the incidence of stillborn piglets. The farrowing duration of sows increased as the number of stillborn piglets increased.