第五十九期：热应激影响生长猪的氨基酸表观回肠消化率和标准回肠消化率

畜牧编辑

　　第五十九期：热应激影响生长猪的氨基酸表观回肠消化率和标准回肠消化率

　　2016. J. Anim. Sci. 94(8): 3362-3369

　　热应激影响生长猪的氨基酸表观回肠消化率和标准回肠消化率

　　A. Morales, M. Pérez, P.Castro, N. Ibarra, H. Bernal, L. H. Baumgard和 M. Cervantes

　　热应激似乎能损害猪小肠的消化和吸收能力，从而可能影响氨基酸消化率。

　　一个交叉设计的实验在8头猪（初始体重为30.8kg）的回肠末端插入T形插管后以7天为周期，饲喂两个周期来分析热应激对采食小麦-豆粕型日粮猪的氨基酸表观回肠消化率和标准回肠消化率的影响。整个试验过程中每隔15分钟对皮下和回肠腔温度进行持续不断的监测。手术恢复后，所有猪只适应了日粮并且训练采食相同数量的饲料，一天进食两次，热中性环境(22°C ± 2°C)下饲养5天。接下来，猪只分为两组（每组四头）；一组仍维持在热中性环境，另一组暴露于自然状态下的热应激环境(24°C 至 45°C) 下饲养7天（周期1）。在周期2中，这两组交换饲养环境。每个周期的第6天和第7天，7点开始对回肠食糜持续收集12h，氧化铬作为肠道食糜流量的指示剂。热应激环境下猪只皮下和回肠温度与热中性环境下相比分别增加了1.3℃和1.6℃ (P < 0.001)。热中性和热应激环境下猪只的氨基酸表观回肠消化率 (%) 分别为Arg，90.6，88.1； His，88.7，85.9；Ile，84.8，83.9；Leu，86.9，84.1；Lys，86.8，86.2；Met，89.8，89.1；Phe，86.0，84.8；Thr，76.7，74.3；Val，82.8，81.7。热中性和热应激环境下猪只的氨基酸标准回肠消化率 (%) 分别为 Arg，94.0，92.0；His，92.5，90.2；Ile，89.5，88.1；Leu，90.1，88.6；Lys，91.0，90.1；Met，94.4，93.6；Phe，90.4，88.9；Thr，86.0，83.7；Val，88.1，86.5。热应激环境下猪只的Arg、His和 Leu 的表观回肠消化率更低一些(P < 0.01)，且热应激环境下猪只Arg和His的标准回肠消化率也更低。其余必需氨基酸的表观回肠消化率和标准回肠消化率都没有受到热应激的影响。

　　总结起来，暴露于自然状态下热应激环境中猪只对必需氨基酸的消化率受到不同的影响，因此，当为热应激环境下的猪只设计日粮的时候要特别注意Arg和His。

　　Heat stress affects the apparent and standardized ileal digestibilities of amino acids in growing pigs

　　A. Morales, M. Pérez, P. Castro, N. Ibarra,H. Bernal, L. H. Baumgard and M. Cervantes

　　Heat stress (HS) appears to impair the pig’s small intestine digestive and absorptive capacities and, therefore, may affect the AA digestibilities.

　　A crossover-designed experiment was conducted utilizing two 7-d periods with 8 pigs (30.8 kg initial BW) surgically fitted with T-type cannulas at the terminal ileum to analyze the effect of HS on both apparent (AID) and standardized (SID) ileal digestibility of AA in pigs fed a wheat–soybean meal diet. Subcutaneous skin and ileal lumen temperatures were continuously monitored in 15-min intervals during the entire experiment. After recovery from surgery, all pigs were adapted to the diet and trained to consume the same amount of feed twice a day for 5 d in thermal-neutral (TN) conditions (22°C ± 2°C). Following adaptation, pigs were divided into 2 groups (4 pigs each)；1 remained in TN conditions, and the other group was exposed to natural HS (24°C to 45°C) for 7 d (period 1). In period 2, the 2 groups switched environments. Ileal digesta were continuously collected for 12 h, starting at 0700 h, on d 6 and 7 of each period. Chromic oxide was used as an indicator of intestinal digesta flow. The subcutaneous and the ileal temperatures were increased between 1.3°C and 1.6°C in HS compared to TN pigs (P < 0.001). TheAID of AA (%) for the TN and HS pigs were Arg, 90.6, 88.1; His, 88.7, 85.9; Ile, 84.8, 83.9; Leu, 86.9, 84.1; Lys, 86.8, 86.2; Met, 89.8, 89.1; Phe, 86.0, 84.8; Thr, 76.7, 74.3; and Val, 82.8, 81.7, respectively. The SID (%) of AA for the TN and HS pigs were Arg, 94.0, 92.0; His, 92.5, 90.2; Ile, 89.5, 88.1; Leu,90.1, 88.6; Lys, 91.0, 90.1; Met, 94.4, 93.6; Phe, 90.4, 88.9; Thr, 86.0, 83.7; and Val, 88.1, 86.5, respectively. The AID of Arg, His, and Leu was lower (P< 0.01) in HS pigs, and the SID of Arg and His was also lower in HS pigs. Neither the AID nor the SID of the remaining essential AA was affected by HS.

　　In summary, the digestibility of essential AA is differentially affected in pigs exposed to natural HS, and thus, special attention should be given to Arg and His when formulating diets for growing pigs under HS conditions。

　　翻译：李光然 来源：猪营养国际论坛CSIS