Uterine spaciousness during embryo and fetal development in multiparous sows improves birth weight and postnatal growth performance

The offspring of unilaterally cauterized (CAUT) and non-cauterized control (CTRL) sows were used to study the effects of increased uterine space on postnatal average daily gain (ADG), backfat and loin depth, mortality, and adrenocorticotrophic hormone (ACTH) induced cortisol response. At gestation day (D) 35, the total number of embryos was significantly decreased in CAUT sows (CAUT=9.1±3.0, CTRL=15.3±4.3; P=0.001). At birth, piglet weight (WTD0), gender, and morphometrics were recorded. Offspring were weighed at D21 of age, weaning, week (W) 7, 12, 16, and 19 of age. Average daily gain (ADG) was calculated during the lactation (ADGLACT; 0-21days), up to weaning (ADGWEAN, 1-3W), nursery (ADGNUR, 3-7W), finisher (ADGFIN, 7-19W), and birth to market (ADGLIFETIME, 0-19W) periods. P2 backfat (BF) and loin eye (LOIN) depth were measured ultrasonically at 70 and 110 kg live weight. Saliva samples were collected from offspring following 5 IU/kg ACTH challenge at W12 and W20 of age. Offspring from CAUT sows were heavier than CTRL at birth and D21 (P<0.05), and trended higher at W7 (P=0.06). ADGLACT and ADGWEAN were higher in CAUT pigs (P<0.05). Pigs with higher ADGLACT had higher ADGLIFETIME (P<0.001) after controlling for WTD0. WTD0 however, was the most consistent factor affecting ADG in all growth periods assessed. We conclude that the postnatal growth benefits of additional uterine space associated with a reduction in intrauterine crowding are primarily mediated through increased birth weight. Moreover, improving lactational growth rate can help offset the poor lifetime growth rates of low birth weight piglets.