飼喂高精料玉米秸稈型日糧增加奶牛瘤胃中內(nèi)毒素的釋放和乳腺中炎性細(xì)胞因子的生成

周俊　董國(guó)忠　敖長(zhǎng)金　章森　邱敏

摘 要：該研究旨在探討飼喂高精料玉米秸稈型日糧對(duì)奶牛瘤胃中內(nèi)毒素釋放和乳腺中炎性細(xì)胞因子生成的影響。選擇30頭產(chǎn)奶量相似（24.32±3.86 kg/d）、體重相近（542.7±56.5 kg）、體況良好（體況評(píng)分2.86±0.29）、處于泌乳中期的經(jīng)產(chǎn)（2～4胎）中國(guó)荷斯坦奶牛，隨機(jī)分為3組（每組n=10），各組飼喂不同的日糧：（1）低精料混合粗飼料日糧（LCF，精粗比為46∶54）。（2）高精料玉米秸稈日糧（HCS，精粗比為65∶35，營(yíng)養(yǎng)水平除纖維外與LCF相同）。（3）低精料玉米秸稈日糧（LCS；精粗比與LCF相同，為46∶54；但營(yíng)養(yǎng)水平低于LCF和LCS）。試驗(yàn)持續(xù)6周，最后一周為樣品采集期。結(jié)果顯示，飼喂HCS的奶牛瘤胃中和糞中內(nèi)毒素含量顯著高于飼喂LCS和LCF的奶牛；飼喂HCS的奶牛乳腺動(dòng)脈血漿中內(nèi)毒素含量顯著高于飼喂LCS的奶牛；與LCS比較，HCS顯著增加了乳腺中白細(xì)胞介素（IL）-1β、IL-6和IL-8的生成；乳腺動(dòng)脈血漿中內(nèi)毒素含量與泌乳效率呈負(fù)相關(guān)。結(jié)果表明，飼喂高精料玉米秸稈型日糧提高了奶牛瘤胃中和糞中內(nèi)毒素的含量，增加了進(jìn)入奶牛乳腺的內(nèi)毒素?cái)?shù)量，從而促進(jìn)了奶牛乳腺中炎性細(xì)胞因子的生成。結(jié)果揭示，飼喂高精料玉米秸稈型日糧誘導(dǎo)乳腺發(fā)生了炎性反應(yīng)，從而在一定程度上降低了奶牛的泌乳效率。

關(guān)鍵詞：內(nèi)毒素 細(xì)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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