Zhang S, Johnson J S, Trottier N L
Department of Animal Science, Michigan State University, East Lansing, 48824 USA.
USDA-ARS Livestock Behavior Research Unit, West Lafayette, 47907 USA.
J Anim Sci Biotechnol. 2020 Jul 9;11:75. doi: 10.1186/s40104-020-00483-w. eCollection 2020.
Reduced protein diet manifested potential to mitigate heat production based on the concept of ideal amino acid profile. The hypothesis of this study was that lactating sows fed a low crude protein (LCP) diet with supplemental amino acid produce less heat compared to those fed a high crude protein (HCP) diet under both thermal neutral (TN) and heat stress (HS) conditions.
Thirty-two lactating sows were allotted to HCP (193 g CP/kg) and LCP (140 g CP/kg) diets under thermal neutral (TN, 21 ± 1.5 °C) or cycling heat stress (HS, 32 ± 1.5 °C daytime and 24 ± 1.5 °C nighttime) conditions. Diets contained 0.90% SID lysine and 10.8 MJ/kg net energy. Positive pressure indirect calorimeters were used to measure gas exchange in individual sows with litters, and individual piglets on days 4, 8, 14 and 18. Sow and litter weights were recorded on days 1, 10 and 21.
Sow total heat production (THP) was calculated by subtracting litter THP from sow + litter THP based on BW. Sow BW and body protein (BP) loss was greater for LCP diet compared to HCP diet in peak lactation ( < 0.05 and < 0.01, respectively) and throughout the entire lactation period ( < 0.05 and = 0.056, respectively) under HS conditions. Heat-stressed sows fed HCP diet had higher ( < 0.05) rectal temperature at 13:00 ( < 0.05) and 19:00 ( < 0.01), and higher respiration rate at 07:00 ( < 0.05), 13:00 ( < 0.05) and 19:00 ( < 0.05) compared to TN sows fed HCP diet. In sows fed LCP diet, those under HS tended to have higher ( = 0.098) rectal temperature at 13:00 and had higher ( < 0.05) respiration rate at 07:00, 13:00 and 19:00 compared to TN sows. The relationship between daily THP and days in lactation of sows fed LCP diet was quadratic ( < 0.05), with an ascending trend until day 14 and a descending trend from days 14 to 18. Sows fed LCP diet had lower daily THP at day 18 ( < 0.001) compared to those fed the HCP diet under HS conditions.
Reduction in THP in sows fed LCP diet was largely associated with THP on day 18 of lactation under HS conditions. Feeding LCP diets alleviated the increased body temperature in sows under HS conditions throughout lactation, which was accompanied by a reduction in respiration rate. Total heat production is associated with days in lactation, in particular under HS conditions with THP appearing to peak between days 14 and 18.
基于理想氨基酸模式的概念，低蛋白饮食显示出减轻产热的潜力。本研究的假设是，在热中性（TN）和热应激（HS）条件下，与饲喂高蛋白（HCP）日粮的泌乳母猪相比，饲喂低粗蛋白（LCP）日粮并补充氨基酸的泌乳母猪产热更少。
32头泌乳母猪被分配到热中性（TN，21±1.5°C）或循环热应激（HS，白天32±1.5°C，夜间24±1.5°C）条件下的HCP（193 g CP/kg）和LCP（140 g CP/kg）日粮中。日粮含有0.90%的标准回肠可消化赖氨酸和10.8 MJ/kg的净能。使用正压间接测热仪测量带仔猪的个体母猪以及第4、8、14和18天的个体仔猪的气体交换。在第1、10和21天记录母猪和仔猪的体重。
根据体重，通过从母猪+仔猪总产热中减去仔猪总产热来计算母猪总产热（THP）。在热应激条件下，泌乳高峰期LCP日粮组母猪的体重和体蛋白（BP）损失高于HCP日粮组（分别为P<0.05和P<0.01），且在整个泌乳期均如此（分别为P<0.05和P = 0.056）。与热中性条件下饲喂HCP日粮的母猪相比，热应激条件下饲喂HCP日粮的母猪在13:00时直肠温度更高（P<0.05），在19:00时更高（P<0.01），在07:00、13:00和19:00时呼吸频率更高（P<0.05）。在饲喂LCP日粮的母猪中，与热中性条件下的母猪相比，热应激条件下的母猪在13:00时直肠温度趋于更高（P = 0.098），在07:00、13:00和19:00时呼吸频率更高（P<0.05）。饲喂LCP日粮的母猪每日总产热与泌乳天数的关系呈二次曲线（P<0.05），直到第14天呈上升趋势，从第14天到第18天呈下降趋势。与热应激条件下饲喂HCP日粮的母猪相比，饲喂LCP日粮的母猪在第18天时每日总产热更低（P<0.001）。
热应激条件下，饲喂LCP日粮的母猪总产热的降低在很大程度上与泌乳第18天的总产热有关。在整个泌乳期，饲喂LCP日粮可缓解热应激条件下母猪体温的升高，同时呼吸频率降低。总产热与泌乳天数有关，特别是在热应激条件下，总产热似乎在第14天至18天达到峰值。
