Evaluating the effects of in utero heat stress on piglet physiology and behavior following weaning and transport

Authors: BYRD, CHRISTOPHER - Purdue University; CHAPEL, NICHOLE - Purdue University; LUGAR, DREW - Purdue University; SAFRANSKI, TIMOTHY - University Of Missouri; LUCY, MATTHEW - University Of Missouri; Johnson, Jay

Submitted to: Animals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2019
Publication Date: 4/24/2019
Citation: Byrd, C., Chapel, N., Lugar, D., Safranski, T., Lucy, M., Johnson, J.S. 2019. Evaluating the effects of in utero heat stress on piglet physiology and behavior following weaning and transport. Animals. 9(4):191. https://doi.org/10.3390/ani9040191.
DOI: https://doi.org/10.3390/ani9040191

Interpretive Summary: Transporting weaned piglets from the farrowing house to a nursery or grow/finish site is a common but stressful procedure in United States swine production. Piglets removed from the sow at weaning undergo feed and water withdrawal during transportation, which is further compounded by an abrupt change from a liquid to solid diet upon arrival at their destination. As a result, newly weaned and transported piglets exhibit reduced body weight and signs of dehydration post-transport. Unfortunately, in utero stress can modify the offspring’s physiological, immune, and behavioral responses during postnatal life and may pre-dispose animals to a greater stress response when exposed to novel postnatal procedures such as weaning and transport. Specifically, in utero heat stress alters swine physiology, metabolism, and body temperature. Therefore, the objective of this preliminary study was to evaluate the effects of in utero heat stress on the behavior and physiology of piglets following weaning and transport. We hypothesized that in utero heat-stressed piglets would exhibit a greater behavioral and physiological stress response following weaning and transportation. Additionally, in utero heat-stressed piglets were expected to show physiological signs of metabolic stress. It was determined that in utero heat-stressed piglets had altered behavior after weaning and transport and maintained a reduction in stress hormones following weaning and transport. Furthermore, in utero heat-stressed pigs displayed post-absorptive metabolic alterations indicating an increase in energy requirements. Future studies should incorporate a larger sample size to confirm these results.

Technical Abstract: Twelve, first-parity gilts were selected for breeding, confirmed pregnant, and allocated to either heat stress (HS; n=6) or thermoneutral (TN; n=6) conditions on d 30-60 of gestation. At weaning, one boar and one barrow of median weight were selected and transported from the University of Missouri (Columbia, MO, USA) to the USDA-ARS Livestock Behavior Research Unit (West Lafayette, IN, USA). Piglets were blocked into pens (n=2/pen) by in utero treatment [in utero heat stress (IUHS, n=12) or in utero thermoneutral (IUTN, n=12)] and sexual status [boar (n=6/in utero treatment) or barrow (n=6/in utero treatment)]. Behavioral data (posture, feeding, drinking, aggression, huddling, and interaction with enrichment) were collected on day (d) 1-7 for 60 min at four different time points (1000 h, 1200 h, 1400 h, 1600 h). Plasma cortisol, non-esterified fatty acids (NEFA), glucose, insulin, and glucose to insulin ratio (I:G) were evaluated 1 d prior to transport (pre-transport), immediately after transport (post-transport), and 7 d after transport (d 7 post-transport). All data were analyzed using the Proc Mixed procedure in SAS 9.4. Overall, IUHS piglets performed more drinking behaviors [0.72 (0.42, 1.10) % vs 0.28 (0.09. 0.58) %, P = 0.05] and tended to perform more aggressive behaviors [0.62 (0.38, 0.92) % vs. 0.33 (0.16, 0.56) %, P = 0.08] than IUTN piglets. No in utero treatment differences were observed for any of the remaining behaviors (P > 0.05). Overall, regardless of in utero treatment, plasma cortisol levels were reduced (P < 0.01) immediately post-transport (39.7 ± 1.8 ng/mL) and d 7 post-transport (39.7 ± 1.8 ng/mL) compared to pre-transport (49.7 ±1.6 ng/mL). In addition, IUHS piglets had reduced cortisol compared to IUTN piglets immediately post-transport and d 7 post-transport (23.7% and 24.6%, respectively, P < 0.01). Non-esterified fatty acids and I:G were not affected by in utero treatment. Insulin and glucose concentrations tended to be reduced pre-transport (P = 0.06 and P = 0.07, respectively) in IUHS (128.0 ± 6.0 and 0.022 ± 0.003, respectively) compared to IUTN (143.9 ± 6.0 and 0.029 ± 0.003, respectively) piglets. In summary, in a preliminary trial, IUHS piglets displayed altered behavioral and physiological responses compared to IUTN piglets following weaning and transport.