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

Kouassi R Kpodo, Alan W Duttlinger, Jacob M Maskal, Jay S Johnson

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 and intestinal morphology in pigs exposed to acute hyperthermia and then rapidly cooled. Twentyfour gilts (78.53 ± 5.46 kg) were exposed to thermoneutral (TN; n = 12 pigs; 21.21 ± 0.31℃; 61.88 ± 6.93% RH) conditions for 6 h, or heat stress (HS; 38.51 ± 0.60℃; 36.38 ± 3.40% RH) conditions 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 per recovery treatment) and one-half of the pigs were not provided feed (NF; n = 6 pigs per 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 and drinking 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, 2.05, 8.32℃, and 88 breaths per min, respectively) in HSC vs. TN pigs, regardless of feeding treatment. Gastrointestinal temperature was greater (P = 0.03; 0.97℃) in HSC + AF vs. HSC + NF pigs from 45 to 180 min of the recovery period. During the recovery period, feeding attempts were greater (P = 0.02; 195.38%) in AF vs. NF pigs. No drinking attempt differences were detected with any comparison (P > 0.05). A decrease (P < 0.01) in jejunum and ileum villus height (24.72% and 26.11%, respectively) and villus height-to-crypt depth ratio (24.03% and 25.29%, respectively) was observed in HSC vs. TN pigs, regardless of feeding treatment. Ileum goblet cells were reduced (P = 0.01; 37.87%) in HSC vs. TN pigs, regardless of feeding treatment. In summary, TGI decreased more rapidly following acute hyperthermia when the feed was removed, and this may have implications toward using feed removal as a strategy to promote acute hyperthermia recovery in pigs.