2 Evaluating the effects of a dietary strategy to mitigate the impact of in utero heat stress on biomarkers of post-absorptive metabolism and stress in pigs following weaning and transport

Abstract

Abstract In utero heat stress (IUHS) increases postnatal energy requirements of pigs, and this may exacerbate weaning and transport stress. The study objective was to evaluate the impact of providing a nutrient dense (ND) diet, which met the greater energy requirements of IUHS pigs, on biomarkers of post-absorptive metabolism and stress following weaning and transport. Twenty-four pregnant gilts were assigned to thermoneutral (n = 12; 17.5 ± 2.1°C) or heat stress (n = 12; cyclical 26°C to 36°C) conditions from gestation d 1 to 58, and then TN conditions until farrowing. At weaning (16.2 ± 0.4 d), mixed-sex piglets (n = 160; 4.78 ± 0.15 kg BW) were transported (loading + transport + unloading) for 11 h 40 min and then blocked into pens (n = 4 piglets/pen) by in utero and dietary treatments fed for 14 d (P1): in utero thermoneutral (IUTN) + control diet (C; n = 10 pens), IUTN + ND (n = 10 pens), IUHS + C (n = 10 pens), IUHS + ND (n = 10 pens). The C diet was fed to all pigs from d 15 to 35 post-weaning and transport (P2). One pig per pen was bled immediately pre-transport (Pre-T) and immediately post-transport (Post-T), and on d 2, 7, 14, 28, and 35 post-weaning and transport to analyze cortisol, glucose, insulin, and non-esterified fatty acids (NEFA). Overall, cortisol was decreased (P = 0.03; 25.8%) during transport in IUHS versus IUTN pigs. On d 2, glucose was decreased overall (P = 0.01; 13.5 mg/dL) in IUHS versus IUTN pigs, but no d 2 insulin (P = 0.76; 0.079 ± 0.011 ng/mL) or NEFA (P = 0.65; 810.3 ± 61.1 mEq/L) differences were detected. Insulin and insulin:glucose ratio were increased (P < 0.04; 0.076 ng/mL and 0.05, respectively) during P1 in ND versus C pigs. In summary, the physiological stress response and glucose levels were altered in IUHS versus IUTN pigs post-weaning and transport, but dietary treatment did not interact with in utero treatment.