Effects of feed removal on thermoregulation and intestinal morphology in pigs recovering from acute hyperthermia

Authors: KPODO, KOUASSI - Purdue University; DUTTLINGER, ALAN - Purdue University; MASKAL, JACOB - Purdue University; Johnson, Jay

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2020
Publication Date: 2/15/2020
Citation: Kpodo, K.R., Duttlinger, A.W., Maskal, J.M., Johnson, J.S. 2020. Effects of feed removal on thermoregulation and intestinal morphology in pigs recovering from acute hyperthermia. Journal of Animal Science. https://doi.org/10.1093/jas/skaa041.
DOI: https://doi.org/10.1093/jas/skaa041

Interpretive Summary: Acute hyperthermia increases health care costs and mortality in pigs and negatively impacts welfare. Unfortunately, pigs are more susceptible to acute hyperthermia than most species due to a lack of functional sweat glands, which is compounded by the inability to utilize wallowing in commercial production settings. To alleviate the negative impacts of acute hyperthermia, different management practices such as increasing barn ventilation, the use of sprinklers and fans, and dietary alterations are used. However, these methods may not be effective during acute hyperthermia. Previous studies by our group determined that rapid cooling without providing feed was effective in quickly reducing core body temperature in pigs and preventing intestinal damage. However, the direct effects of feed withdrawal during and after acute hyperthermia on the body temperature response and intestinal health of pigs is currently unknown. Therefore, the study objective was to evaluate the effects of feed removal on body temperature, feeding behavior, and intestinal health in pigs exposed to acute hyperthermia and then rapidly cooled. We hypothesized that the use of feed removal and rapid cooling would be most effective in alleviating acute hyperthermia through a more rapid reduction in body temperature and the prevention of intestinal damage. It was determined that the use of rapid cooling and feed withdrawal was more effective in rapidly reducing core body after acute hyperthermia when compared to rapid cooling with full feed access, but no effects on intestinal health were observed. These data have positive implications towards the use of feed removal as a strategy to help pigs return to a normal body temperature more rapidly following acute hyperthermia.

Technical Abstract: Feed consumption increases body temperature and may delay a return to euthermia and exacerbate intestinal injury following acute hyperthermia recovery in pigs. Therefore, the study objective was to evaluate the effects of feed removal on body temperature, feeding behavior, and intestinal morphology in pigs exposed to acute hyperthermia and then rapidly cooled. Twenty-four gilts (78.53 ± 5.46 kg) were exposed to thermoneutrality (TN; n = 12 pigs; 21.21 ± 0.31°C; 61.88 ± 6.93% RH) for 6 h, or heat stress (HS; 38.51 ± 0.60°C; 36.38 ± 3.40% RH) for 3 h followed by a 3-h recovery period of rapid cooling (HSC; n = 12 pigs; TN conditions and cold water dousing). Within each recovery treatment, one-half of the pigs were provided feed ad libitum (AF; n = 6 pigs/recovery treatment) and one-half of the pigs were not provided feed (NF; n = 6 pigs/recovery treatment). Gastrointestinal (TGI), vaginal (TV), and skin (Tsk) temperatures, and respiration rate (RR) were recorded every 15 min. Pigs were video-recorded to assess feeding attempts. Immediately following the 6-h thermal stress period pigs were euthanized, and intestinal samples were collected to assess morphology. During the HS period, Tv, TGI, Tsk, and RR were increased (P < 0.01; 1.63°C, 2.05°C, 8.32°C, and 89 breaths per minute, respectively) in HSC versus TN pigs, regardless of feeding treatment. Gastrointestinal temperature was greater (P = 0.03; 0.97°C) in HSC+AF versus HSC+NF pigs from 45-180 min of the recovery period. During the recovery period, feeding attempts were greater (P = 0.02; 197.67%) in AF versus NF pigs. A decrease (P < 0.01) in jejunum and ileum villus height (24.72% and 26.11%, respectively) and villus height-to-crypt depth ratio (24.35% and 25.29%, respectively) was observed in HSC versus TN pigs, regardless of feeding treatment. Ileum goblet cells were reduced (P = 0.01; 37.87%) in HSC versus TN pigs, regardless of feeding treatment. In summary, TGI decreased more rapidly following acute hyperthermia when feed was removed, and this has implications towards using feed removal as a strategy to promote acute hyperthermia recovery in pigs.