2016. J. Anim. Sci. 94(8): 3362-3369
A. Morales, M. Pérez, P.Castro, N. Ibarra, H. Bernal, L. H. Baumgard和 M. Cervantes
熱應激似乎能損害豬小腸的消化和吸收能力，從而可能影響氨基酸消化率。一個交叉設計的實驗在8頭豬（初始體重為30.8kg）的回腸末端插入T形插管后以7天為周期，飼喂兩個周期來分析熱應激對采食小麥-豆粕型日糧豬的氨基酸表觀回腸消化率和標準回腸消化率的影響。整個試驗過程中每隔15分鐘對皮下和回腸腔溫度進行持續不斷的監測。手術恢復后，所有豬只適應了日糧并且訓練采食相同數量的飼料，一天進食兩次，熱中性環境(22°C ± 2°C)下飼養5天。接下來，豬只分為兩組（每組四頭）；一組仍維持在熱中性環境，另一組暴露于自然狀態下的熱應激環境(24°C 至 45°C) 下飼養7天（周期1）。在周期2中，這兩組交換飼養環境。每個周期的第6天和第7天，7點開始對回腸食糜持續收集12h，氧化鉻作為腸道食糜流量的指示劑。熱應激環境下豬只皮下和回腸溫度與熱中性環境下相比分別增加了1.3℃和1.6℃ (P < 0.001)。熱中性和熱應激環境下豬只的氨基酸表觀回腸消化率 (%) 分別為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。熱中性和熱應激環境下豬只的氨基酸標準回腸消化率 (%) 分別為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。熱應激環境下豬只的Arg、His和 Leu 的表觀回腸消化率更低一些(P < 0.01)，且熱應激環境下豬只Arg和His的標準回腸消化率也更低。其余必需氨基酸的表觀回腸消化率和標準回腸消化率都沒有受到熱應激的影響。
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.