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

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 and intestinal morphology in pigs exposed to acute hyperthermia and then rapidly cooled. Twenty-four gilts (78.53 ± 5.46 kg) were exposed to thermoneutral (TN; n = 12 pigs; 21.21 ± 0.31 °C; 61.88 ± 6.93% RH) conditions for 6 h, or heat stress (HS; 38.51 ± 0.60 °C; 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 °C, and 88 breaths per min, respectively) in HSC vs. TN pigs, regardless of feeding treatment. Gastrointestinal temperature was greater (P = 0.03; 0.97 °C) 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.

Effects of Feed Removal during Acute Heat Stress on the Cytokine Response and Short-Term Growth Performance in Finishing Pigs

“…Therefore, the lack of body temperature differences may have been a result of an overall reduction in feed intake in HS + AF pigs that placed them on a similar nutritional plane to the HS + NF pigs and reduced the potential for feeding-induced differences in body temperature. Furthermore, the reasons why the results of the current study contradict previous reports [ 11 , 16 ] may be related to the cooling procedure used or the severity of the heat load imposed. In the previous studies [ 11 , 16 ], pigs were rapidly cooled by cold water dousing following a constant and severe HS.…”

“…Furthermore, the reasons why the results of the current study contradict previous reports [ 11 , 16 ] may be related to the cooling procedure used or the severity of the heat load imposed. In the previous studies [ 11 , 16 ], pigs were rapidly cooled by cold water dousing following a constant and severe HS. However, in the current study, pigs were exposed to cyclic HS to replicate a natural summer production environment and were not rapidly cooled.…”

“…The thermic effect of feeding increases body temperature [ 15 ] and may delay the return to euthermia in pigs recovering from HS. As such, feed removal during HS and subsequent recovery is associated with a more rapid return of body temperature to euthermia [ 11 , 16 ] and may reduce systemic inflammation in pigs [ 16 ]. However, contrary to these reports, no body temperature (T GI and T sk ) differences were detected between the HS + AF and HS + NF pigs in the present study.…”

“…However, feed intake increases immediately after the heat load is removed [ 9 ], and this has the potential to add heat to the body and delay the return to euthermia due to the heat from nutrient processing [ 10 ]. Previous studies in pigs given feed access compared with those not given feed access during HS recovery have demonstrated that the body temperature return to euthermia is delayed [ 11 ], and this may exacerbate the cytokine response since the negative consequences of HS may be related to the intensity and duration of heat exposure and subsequent body temperature increase [ 12 ]. Therefore, the study objective was to evaluate the effects of feed removal during an acute heat event on the cytokine response and the short-term effects on growth performance in finishing pigs.…”

Adverse Effects of Heat Stress on the Intestinal Integrity and Function of Pigs and the Mitigation Capacity of Dietary Antioxidants: A Review

“…Under such conditions, Pearce et al [ 80 ] observed increase in ileum MUC2 after 6 h of exposure to HS which can act as a protective barrier for the intestine and may combat the decrease in intestinal integrity. However, in another study, pigs exposed to HS for 3 h showed a reduction of goblet cells in the jejunum and ileum [ 85 ], and this was also observed even during the recovery period of 7 days after constant exposure to HS for 3 days [ 81 ]. This suggests that mucin glycoprotein (MUC2) production and activity can be reduced as this is produced by the goblet cells which can then potentially compromise intestinal function; that could lead to higher risk of infection caused by increased bacterial adhesion to the epithelium [ 85 , 88 ].…”