高淀粉高油脂饲粮对奶牛粪便发酵参数和菌群多样性的影响

Effects of High Starch-High Oil Diet on Fecal Fermentation Parameters and Bacterial Diversity of Dairy Cows

本试验通过在饲粮中添加粉碎玉米和大豆油,研究高淀粉高油脂饲粮对奶牛粪便发酵参数和菌群多样性的影响。选取泌乳天数[(215±34)d]和体重[(575±23)kg]相近的8头荷斯坦奶牛,随机分为2组,每组4头,采用2×2反转试验设计,分为2期,每期23 d,第2期对照组和试验组对调。每期前16 d对照组奶牛饲喂基础饲粮,试验组奶牛饲喂高淀粉高油脂饲粮;每期后7 d 2组奶牛均饲喂基础饲粮。于每期的第15天采集粪便,测定粪便发酵参数和菌群多样性。结果显示:1)与对照组相比,饲喂高淀粉高油脂饲粮后,奶牛的干物质采食量、粪便评分以及粪便的pH、丙酸浓度和乙酸摩尔比均显著下降(P<0.05),丁酸摩尔比显著上升(P<0.05)。1 d内,随晨饲后时间的延长,2组奶牛粪便pH均呈逐渐上升趋势,各时间点试验组均显著低于对照组(P<0.05);对照组总挥发性脂肪酸(TVFA)浓度呈逐渐下降趋势,试验组则呈先升高后降低趋势,但TVFA浓度未受饲粮处理的显著影响(P>0.05)。2)试验组奶牛粪便菌群的ACE指数、Chao指数和Shannon指数均显著低于对照组(P<0.05)。厚壁菌门、拟杆菌门和放线菌门为2组奶牛粪便菌群中的优势菌门。在门水平上,高淀粉高油脂饲粮显著降低了放线菌门、TM7和疣微菌门的相对丰度(P<0.05),显著提高了变形菌门的相对丰度(P<0.05);在属水平上,高淀粉高油脂饲粮显著降低了瘤胃球菌科未分类属、拟杆菌目未分类属、梭菌目未分类属的相对丰度(P<0.05),显著提高了毛螺旋菌科未分类属和琥珀酸弧菌属的相对丰度(P<0.05)。综上可知,高淀粉高油脂饲粮可降低奶牛的干物质采食量和粪便评分,影响后肠道的发酵参数,降低粪便菌群的丰富度和多样性,存在降低肠道免疫性能和诱发炎症的风险。

The aim of this experiment was to study the effects of high starch-high oil diet on fecal fermentation parameters and bacterial flora diversity of dairy cows by supplementing with ground corn and soybean oil.Eight Holstein cows with similar days in milk[(215±34)d]and body weight[(575±23)kg]were selected and randomly divided into two groups with 4 cows in each group in a 2×2 change-over experiment.The test was divided into two periods,each period was 23 days,and the control group and the test group were switched in the second period.In the first 16 days of each trial period,the cows in the control group were fed a basal diet,the cows in the test group were fed a high starch-high oil diet.In the last 7 days of each trial period,the cows in the two groups were both fed the basal diet.Feces were collected on the 15th day of each test period to determine fecal fermentation parameters and bacterial flora diversity.The results showed as follows:1)after feeding high starch-high oil diet,the dry matter intake(DMI),fecal score,and the fecal pH,propionate concentration and the molar ratio of acetate of dairy cows were significantly decreased(P<0.05),while the molar ratio of butyrate was increased significantly(P<0.05).Within a day,with the extension of time after morning feeding,the fecal pH presented a gradual upward trend,and the test group was significantly lower than the control group at each time point(P<0.05);the concentration of total volatile fatty acids(TVFA)of control group showed a gradual decreasing trend,and that of test group firstly increased and then decreased,but the TVFA concentration was not significantly affected by dietary treatment(P>0.05).2)The ACE index,Chao index and Shannon index in fecal bacterial flora of dairy cows in test group were significantly lower than those in control group(P<0.05).Firmicutes,Bacteroidetes and Actinobacteria were the dominant phyla in fecal bacterial flora of dairy cows in two groups.At the phylum level,the relative abundances of Actinobacteria,TM7 and Verrucomicrobia were decreased significantly(P<0.05),whereas the relative abundance of Proteobacteria was increased significantly when dairy cows fed the high starch-high oil diet(P<0.05).At the genus level,the relative abundances of unclassified_Ruminococcaceae,unclassified_Bacteroidales and unclassified_Clostridiales were significantly decreased(P<0.05),while the relative abundances of unclassified_Lachnospiraceae and Succinivibrio were increased significantly when dairy cows fed the high starch-high oil diet(P<0.05).In conclusion,high starch-high oil diet can reduce the DMI,fecal score,affect the fermentation parameters of hindgut,reduce the richness and diversity of fecal bacterial flora,and have the risk of reducing intestinal immune performance and inducing inflammation in dairy cows.