Evaluation and mitigation of the effects of in utero heat stress on piglet growth performance, post-absorptive metabolism, and stress response following weaning and transport

Authors: MASKAL, JACOB - Purdue University; DUTTLINGER, ALAN - Purdue University; KPODO, KOUASSI - Purdue University; MCCONN, BETTY - Orise Fellow; BYRD, CHRISTOPHER - Purdue University; RICHERT, BRIAN - Purdue University; Marchant, Jeremy; Lay Jr, Donald; PERRY, SHELBI - University Of Missouri; LUCY, MATTHEW - University Of Missouri; SAFRANSKI, TIM - University Of Missouri; Johnson, Jay

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2020
Publication Date: 8/24/2020
Citation: Maskal, J.M., Duttlinger, A.W., Kpodo, K.R., Mcconn, B.R., Byrd, C.J., Richert, B.T., Marchant Forde, J.N., Lay Jr, D.C., Perry, S.D., Lucy, M.C., Safranski, T.J., Johnson, J.S. 2020. Evaluation and mitigation of the effects of in utero heat stress on piglet growth performance, post-absorptive metabolism, and stress response following weaning and transport. Journal of Animal Science. https://doi.org/10.1093/jas/skaa272.
DOI: https://doi.org/10.1093/jas/skaa272

Interpretive Summary: In utero heat stress negatively impacts swine health and productivity throughout their entire lifespan. Negative effects range from decreased growth performance and meat quality to reduced reproductive efficiency and greater stress and disease susceptibility. The decrease in growth performance and increased stress response of in utero heat-stressed pigs may be partially due to increased energy requirements compared to in utero thermoneutral counterparts. Therefore, the experimental objective was to determine whether providing newly weaned and transported in utero heat-stressed pigs with higher energy nutrient dense diets would improve growth performance and decrease stress during the nursery phase of growth. We determined that increasing the energy content of the diet did not improve growth performance of the in utero heat-stressed pigs as average daily body weight gain was reduced overall when compared to in utero thermoneutral controls. This response was likely due to the fact that pigs provided the nutrient dense diet voluntarily reduced their feed intake so that total energy consumed was similar to that of the control diet fed pigs. The decrease in body weight gain for the in utero heat-stressed pigs was accompanied by metabolic alterations that prevented them from mobilizing energy reserves following weaning and transport when compared to in utero thermoneutral pigs. Overall, these data indicate that in utero heat stress is detrimental to future pig growth performance and health, especially during times of increased stress such as weaning and transport. Furthermore, the negative impact on growth performance is not rescued by the provision of more nutrient dense diets.

Technical Abstract: In utero heat stress (IUHS) increases pig energy requirements during postnatal life, and this may compound weaning and transport stress. The study objective was to evaluate and mitigate the negative effects of IUHS on piglet performance, metabolism, and stress following weaning and transport through the provision of a nutrient dense (ND) nursery diet formulated to meet the greater energy requirements of IUHS pigs. Twenty-four pregnant gilts were exposed to thermoneutral (TN; n = 12; 17.5 ± 2.1°C) or heat stress (HS; n = 12; cycling 26°C to 36°C) conditions for the first half of gestation (d 6 to 59) and then TN conditions (20.9 ± 2.3°C) until farrowing. At weaning (16.2 ± 0.4 d), mixed-sex piglets (N = 160; 4.78 ± 0.15 kg BW) were transported for 11 h 40 min. Upon arrival to the nursery, piglets were blocked into pens (n = 4 pigs/pen) by in utero and dietary treatments: 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). Treatment diets were fed from d 1 to 14 post-weaning and transport (Period 1), and the C diet was fed to all pigs from d 15 to 35 post-weaning and transport (Period 2). Production measures were taken in 7-d intervals to calculate average daily gain (ADG), average daily feed intake (ADFI), average daily energy intake (ADEI), gain:feed, and gain:energy intake. Blood samples were collected prior to transport (Pre-T), immediately following 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). Behavior was assessed through video-recording on d 3, 5, 8, 11, and 13 post-weaning and transport. Data were analyzed using PROC GLIMMIX in SAS 9.4. In Period 1, ADG was reduced (P = 0.03; 10.9 g/d) in IUHS vs. IUTN pigs. Pigs fed ND diets had reduced ADFI (P = 0.02; 8.9%) compared to C diet fed pigs during Period 1, which resulted in similar ADEI (P = 0.24; 1,115 ± 46 kcal/d). During transport, cortisol was decreased (P = 0.03; 25.8%) in IUHS vs. IUTN pigs. On d 2, glucose was decreased (P = 0.01; 13.5 mg/dL) in IUHS vs. IUTN pigs. No in utero treatment-related behavioral differences were observed, but lying behavior was reduced (P = 0.03; 4.4%) and standing behavior was increased (P = 0.04; 4.0%) in ND vs. C pigs. In summary, IUHS reduced growth performance in pigs following weaning and transport and providing a ND diet did not rescue lost performance.