饲喂高精料玉米秸秆型日粮增加奶牛瘤胃中内毒素的释放和乳腺中炎性细胞因子的生成

周俊　董国忠　敖长金　章森　邱敏

摘 要：该研究旨在探讨饲喂高精料玉米秸秆型日粮对奶牛瘤胃中内毒素释放和乳腺中炎性细胞因子生成的影响。选择30头产奶量相似（24.32±3.86 kg/d）、体重相近（542.7±56.5 kg）、体况良好（体况评分2.86±0.29）、处于泌乳中期的经产（2～4胎）中国荷斯坦奶牛，随机分为3组（每组n=10），各组饲喂不同的日粮：（1）低精料混合粗饲料日粮（LCF，精粗比为46∶54）。（2）高精料玉米秸秆日粮（HCS，精粗比为65∶35，营养水平除纤维外与LCF相同）。（3）低精料玉米秸秆日粮（LCS；精粗比与LCF相同，为46∶54；但营养水平低于LCF和LCS）。试验持续6周，最后一周为样品采集期。结果显示，饲喂HCS的奶牛瘤胃中和粪中内毒素含量显著高于饲喂LCS和LCF的奶牛；饲喂HCS的奶牛乳腺动脉血浆中内毒素含量显著高于饲喂LCS的奶牛；与LCS比较，HCS显著增加了乳腺中白细胞介素（IL）-1β、IL-6和IL-8的生成；乳腺动脉血浆中内毒素含量与泌乳效率呈负相关。结果表明，饲喂高精料玉米秸秆型日粮提高了奶牛瘤胃中和粪中内毒素的含量，增加了进入奶牛乳腺的内毒素数量，从而促进了奶牛乳腺中炎性细胞因子的生成。结果揭示，饲喂高精料玉米秸秆型日粮诱导乳腺发生了炎性反应，从而在一定程度上降低了奶牛的泌乳效率。

关键词：内毒素 细胞因子 乳腺 奶牛

Abstract：The objective of this study was to investigate the effects of feeding a high-concentrate corn straw diet on the release of endotoxin in the rumen and pro-inflammatory cytokines in the mammary gland of dairy cows in comparison with a low-concentrate corn straw diet and a low-concentrate quality forage diet. Thirty multiparous mid-lactation Chinese Holstein cows with a body condition score of 2.86 ± 0.29， weighing 543 ± 57 kg and producing 24.32 ± 3.86 kg/d milk， were randomly assigned to 1 of the 3 diets （n = 10）：（1） low-concentrate mixed quality forage diet （LCF） with a concentrate to roughage ratio of 46∶54.（2）high-concentrate corn straw diet （HCS） with a concentrate to roughage ratio of 65∶35 and identical nutrient levels （except fiber） with LCF.（3）low-concentrate corn straw diet （LCS） with the same concentrate to roughage ratio （46∶54） as LCF but lower nutrient levels than both LCF and HCS. The experiment lasted 6 weeks， and samples were collected on the last week. Concentrations of endotoxin in rumen fluid and feces of cows fed HCS were significantly higher than those of cows fed LCS and LCF. Contents of endotoxin in mammary arterial and venous plasma in cows fed HCS were significantly higher than in cows fed LCS. Feeding HCS increased the release of IL-1β， IL-6 and IL-8 in the mammary gland compared with feeding LCS. Concentrations of endotoxin in mammary arterial plasma had a negative correlation with milk production efficiency. Results indicated that the high-concentrate corn straw diet increased the concentrations of endotoxin in rumen fluid and feces. Furthermore， feeding the high-concentrate corn straw diet increased entry of endotoxin into the mammary gland， which in turn stimulated the mammary gland to release more pro-inflammatory cytokines. The results may suggest that feeding a high-concentrate corn straw diet induce a higher pro-inflammatory response in the mammary gland and thus may partly decrease the milk production efficiency in dairy cows.

Key Words：Endotoxin；Cytokine；Mammary gland；Dairy cow

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