24頭豬只中（78.53±5.46kg）12頭豬只暴露于熱中性（TN組，21.21±0.3℃；61.88±6.93% RH）條件下6 h；12頭豬只在熱應激（HS，38.51±0.60℃；36.38±3.40% RH）條件下3h，隨后3h快速降溫恢復（HSC組，TN條件和冷水降溫）。每個處理組中，恢復期時半數的豬只提供飼糧供其自由采食（AF，n=6），剩余半數豬只不提供飼糧（NF，n=6）。每15分鐘記錄胃腸道（TGI）、陰道（TV）、皮膚（TSK）溫度和呼吸率（RR）。對豬的采食和飲水嘗試進行了視頻記錄。在6h的熱應激期之后，立即對豬實施安樂死，并收集腸道樣本以評估其形態。
數據顯示，在不考慮飼喂的情況下，與TN組相比，HSC組豬只HS期間，TV、TGI、TSK、RR均提高（P < 0.01，1.63、2.05、8.32℃和每分鐘88次）。與HSC+NF相比，在恢復期的45 ~ 180分鐘內，HSC + AF豬只TGI溫度升高（P = 0.03，0.97℃）。在恢復期內，與NF豬只相比，AF豬只采食嘗試更多（P = 0.02，195.38%）。飲水嘗試次數無差異（P > 0.05）。無論飼喂日糧與否，與TN組相比，HSC組豬只空回腸絨毛高度和絨毛高度：隱窩深度比值下降（P < 0.01，分別為24.72%和26.11%；24.03%和25.29%）；回腸杯狀細胞也減少了（P = 0.01，37.87%）。
Effects of feed removal on thermoregulation and intestinal morphology in pigs recovering from acute hyperthermia
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.