24头猪只中（78.53±5.46kg）12头猪只暴露于热中性（TN组，21.21±0.3℃；61.88±6.93% RH）条件下6 h；12头猪只在热应激（HS，38.51±0.60℃；36.38±3.40% RH）条件下3h，随后3h快速降温恢复（HSC组，TN条件和冷水降温）。每个处理组中，恢复期时半数的猪只提供饲粮供其自由采食（AF，n=6），剩余半数猪只不提供饲粮（NF，n=6）。每15分钟记录胃肠道（TGI）、阴道（TV）、皮肤（TSK）温度和呼吸率（RR）。对猪的采食和饮水尝试进行了视频记录。在6h的热应激期之后，马上对猪实施安乐死，并收集肠道样本以评估其形态。
数据显示，在不考虑饲喂的情况下，与TN组相比，HSC组猪只HS期间，TV、TGI、TSK、RR均提高（P < 0.01，1.63、2.05、8.32℃和每分钟88次）。与HSC+NF相比，在恢复期的45 ~ 180分钟内，HSC + AF猪只TGI温度升高（P = 0.03，0.97℃）。在恢复期内，与NF猪只相比，AF猪只采食尝试更多（P = 0.02，195.38%）。饮水尝试次数无差异（P > 0.05）。无论饲喂日粮与否，与TN组相比，HSC组猪只空回肠绒毛高度和绒毛高度：隐窝深度比值下降（P < 0.01，分别为24.72%和26.11%；24.03%和25.29%）；回肠杯状细胞也减少了（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.