Department of Animal Science, Iowa State University, Ames, IA 50011, USA.
School of Animal Science, Virginia Tech, Blacksburg, VA 24061, USA.
Animal. 2024 Jun;18(6):101168. doi: 10.1016/j.animal.2024.101168. Epub 2024 Apr 23.
Heat stress (HS) negatively impacts a variety of production parameters in growing pigs; however, the impact of biological sex on the HS response is largely unknown. To address this, 48 crossbred barrows and gilts (36.8 ± 3.7 kg BW) were individually housed and assigned to one of three constant environmental conditions: (1) thermoneutral (TN) (20.8 ± 1.6 °C; 62.0 ± 4.7% relative humidity; n = 8/sex), (2) HS (39.4 ± 0.6 °C; 33.7 ± 6.3% relative humidity) for 1 d (HS1; n = 8/sex), or (3) or for 7 d (HS7; n = 8/sex). As expected, HS increased rectal temperature (Tr) following 1 d of HS (1.0 °C; P < 0.0001) and 7 d of HS (0.9 °C; P < 0.0001). By 7 d, heat-stressed gilts were cooler than barrows (0.4 °C; P = 0.016), despite identical heating conditions. There was a main effect of sex such that barrows had higher Tr than gilts (P = 0.031). Heat-stressed pigs on d 1 had marked reductions in feed intake and BW compared to TN (P < 0.0001). One day of HS resulted in negative gain to feed (G:F) in barrows and gilts and was reduced compared to TN (P < 0.0001). Notably, following 1 d of HS, the variability of G:F was greater in gilts than in barrows. Between 1 and 7 d of HS, G:F improved in barrows and gilts and were similar to TN pigs, even though HS barrows had higher Tr than gilts over this period. Heat stress for 1 and 7 d reduced empty gastrointestinal tract weight compared to TN (P < 0.0001). Interestingly, HS7 gilts had decreased gastrointestinal tract weight compared to HS1 gilts (2.43 vs 2.72 kg; P = 0.03), whereas it was similar between HS1 and HS7 barrows. Lastly, a greater proportion of gastrointestinal contents was in the stomach of HS1 pigs compared to TN and HS7 (P < 0.05), which is suggestive of decreased gastric emptying. Overall, HS barrows maintained an elevated Tr compared to HS gilts through the duration of the experiment but also maintained similar growth and production metrics compared to gilts, despite this higher temperature.
热应激（HS）会对生长猪的多种生产参数产生负面影响；然而，生物性别对 HS 反应的影响在很大程度上尚不清楚。为了解决这个问题，将 48 头杂交公猪和母猪（36.8±3.7kgBW）单独饲养，并分配到三种恒定环境条件之一：（1）常温（TN）（20.8±1.6°C；62.0±4.7%相对湿度；n=8/性别），（2）HS（39.4±0.6°C；33.7±6.3%相对湿度）持续 1 天（HS1；n=8/性别），或（3）或持续 7 天（HS7；n=8/性别）。正如预期的那样，HS1 天和 HS7 天后，HS 增加了直肠温度（Tr）（分别为 1.0°C；P<0.0001 和 0.9°C；P<0.0001）。到第 7 天，尽管加热条件相同，但受热应激的母猪比公猪更凉爽（0.4°C；P=0.016）。存在性别主要效应，即公猪的 Tr 高于母猪（P=0.031）。第 1 天热应激的猪与 TN 相比，采食量和 BW 明显减少（P<0.0001）。1 天的 HS 导致公猪和母猪的增重到饲料（G：F）出现负增长，与 TN 相比减少（P<0.0001）。值得注意的是，在 1 天的 HS 之后，母猪的 G：F 变异性大于公猪。在 HS1 和 HS7 之间 1-7 天，公猪和母猪的 G：F 得到改善，与 TN 猪相似，尽管在此期间 HS 公猪的 Tr 高于母猪。1 天和 7 天的 HS 导致空胃肠重量比 TN 减少（P<0.0001）。有趣的是，与 HS1 母猪相比，HS7 母猪的胃肠道重量减少（2.43 与 2.72kg；P=0.03），而 HS1 和 HS7 公猪之间相似。最后，HS1 猪的胃中有更多的胃内容物，与 TN 和 HS7 相比（P<0.05），这表明胃排空减少。总体而言，与 HS 母猪相比，HS 公猪在整个实验过程中保持较高的 Tr，但与母猪相比，也保持相似的生长和生产指标，尽管温度较高。
