饲粮中全棉籽比例对育肥荷斯坦公牛瘤胃发酵与微生物区系、甲烷排放及肝脏碳代谢相关基因表达的影响

摘要

本试验旨在研究饲粮中全棉籽比例对育肥荷斯坦公牛瘤胃发酵与微生物区系、甲烷排放及肝脏碳代谢相关基因表达的影响.选取44头体重相近、健康的育肥荷斯坦公牛,随机分为4组,每组11头,各组平均体重差异不显著( P＞0.05) .Ⅰ(对照) 、Ⅱ、Ⅲ和Ⅳ组公牛分别饲喂含有0、5%、10%和15%全棉籽的饲粮.各组饲粮能量和粗蛋白质水平基本相同.试验期为90 d.结果表明:1)在瘤胃发酵参数中,与Ⅰ组相比,Ⅳ组的氨态氮、微生物蛋白浓度以及乙酸和丙酸比例分别提高了 31.34%、 40.00%、 2.26%和 15.20%( P＜0.05 ) ,丁酸比例降低了 4.46%( P＜0.05) ,乙酸/丙酸和pH无显著变化( P＞0.05) . 2)从瘤胃细菌属水平的相对丰度分析,Ⅳ组中普雷沃氏菌属－1、密螺旋体属－2的相对丰度极显著高于Ⅰ、Ⅱ、Ⅲ组( P＜0.01);Ⅳ组的琥珀酸弧菌科UCG?002的相对丰度显著高于Ⅰ组( P＜0.05) ;理研菌科 RC9 肠道群、普雷沃氏菌科UCG003、瘤胃杆菌属、疣微菌科NK4A214群、纤维杆菌属、未识别的叶绿体和拟杆菌属的相对丰度各组间的差异均不显著( P＞0.05) . 3)从瘤胃产甲烷古菌属水平的相对丰度分析,Ⅳ组甲烷短杆菌属、甲烷丝状菌属的相对丰度均为4组中最低,并显著低于Ⅰ组( P＜0.05) ;Ⅲ组Ab?sconditabacteria unidentified SR1的相对丰度最高,显著高于Ⅰ组( P＜0.05) ;甲烷球形菌属、甲烷微球菌属、甲烷螺菌属的相对丰度各组间均未表现出显著差异(P＞0.05). 4)饲粮中添加不同比例的全棉籽均降低了育肥荷斯坦公牛的甲烷排放量,其中Ⅳ组的甲烷排放量比Ⅰ组降低了22.68%( P＜0.05) . 5)相关分析发现,育肥荷斯坦公牛的平均日增重与甲烷排放量呈显著负相关( P＜0.05) ,甲烷短杆菌、甲烷丝状菌和琥珀酸弧菌科菌群的相对丰度与甲烷排放量呈显著或极显著正相关( P＜0.05或P＜0.01) . 6)饲粮中添加15%的全棉籽后,育肥荷斯坦公牛肝脏中甲基丙二酸单酰辅酶A变位酶( MUT) 、磷酸烯醇式丙酮酸羧激酶( PEPCK)和葡萄糖－6－磷酸酶(G6P)的mRNA表达量均呈上调趋势,其中MUT的mRNA表达量极显著高于Ⅰ组( P＜0.01) , PEPCK的mRNA表达量显著高于Ⅰ组( P＜0.05) .综上所述,在本试验条件下,饲粮中添加15%的全棉籽可有效调控荷斯坦公牛瘤胃发酵及微生物区系,显著降低甲烷排放量以及上调肝脏中碳代谢相关基因的表达.%This experiment was aimed to study the effects of dietary whole cottonseed ratio on rumen fermenta?tion and microflora, methane emission and expression of genes related to carbon metabolism in liver of fatte?ning Holstein bulls. Forty?four fattening healthy Holstein bulls with similar body weight were randomly divided into 4 groups with 11 heads in each group. The difference of average body weight was not significant among groups ( P＞0.05). The bulls in groupsⅠ( control) ,Ⅱ,Ⅲ, andⅣ were fed diets contained 0, 5%, 10%, and 15% whole cottonseed, respectively. The dietary energy and crude protein levels of each group were basi?cally the same. The experimental period lasted for 90 d. The results showed as follows: 1) in the rumen fer?mentation parameters, compared with group Ⅰ, the concentrations of ammonia nitrogen, microbial protein, and the percentages of acetic acid and propanoic acid in groupⅣwere increased by 31.34%, 40.00%, 2.26%and 15.20%, respectively ( P＜0.05) , and the percentage of butyric acid was decreased by 4.46%( P＜0.05) , but the acetic acid/propanoic acid and pH had no significant changes ( P＞0.05). 2) From the analysis of the relative abundances of rumen bacteria at genus level, the relative abundances of Prevotella_1 and Treponema_2 in group Ⅳ were extremely significantly higher than those in groupsⅠ,Ⅱ and Ⅲ( P＜0.01) ; the relative a?bundance of Succinivibrionaceae_UCG?002 in group Ⅳ was significantly higher than that in group Ⅰ( P＜0.05) ; there were no significant differences in the relative abundances of Rikenellaceae_RC9_gut_ group, Pre?votellaceae_UCG?003, Ruminobacter, Ruminococcaceae_NK4A214_ group, Fibrobacter, Unidentified Chlo?roplast and Bacteroides ( P＞0.05). 3) From the analysis of the relative abundances of rumen methanogens at genus level, the relative abundances of Methanobrevibacter and Methanosaeta in groupⅣwere the lowest in 4 groups, and significantly lower than that in group Ⅰ( P＜0.05) ; group Ⅲ had the highest relative abundance of Absconditabacteria_unidentified_SR1, and significantly higher than that in group Ⅰ( P＜0.05) ; there were no significant differences in the relative abundances of Methanosphaera, Methanimicrococcus and Methanospi?rillum ( P＞0.05). 4) Dietary supplemented with different ratios of whole cottonseed all decreased the methane emission of fattening Holstein bulls, and methane emission in group Ⅳ was decreased by 22.68% compared with group Ⅰ( P＜0.05). 5) Correlation analysis found that the average daily weight had significant negative correlation with methane emission ( P＜0.05) , and the relative abundances of Methanobrevibacter, Methano?saeta and Succinivibrionaceae_UCG?002 had significant or extremely significant positive correlation with meth?ane emission ( P＜0.05 or P＜0.01). 6) After adding 15% of whole cottonseed into the diet, the mRNA ex?pression levels of methylmalonyl coenzyme amutase ( MUT) , phosphoenolpyruvate carboxykinase ( PEPCK) and glucose?6?phosphatase ( G6P) in liver had upward trend, and the MUT and PEPCK mRNA expression lev?els were significantly or extremely significant higher than those in groupⅠ( P＜0.05 or P＜0.01). To sum up, under the conditions of this experiment, adding 15% whole cottonseed into the diet can effectively regulate the rumen fermentation and microflora of fattening Holstein bulls, significantly reduce the methane emission and up?regulate the expression of carbon metabolism related genes in the liver.[ Chinese Journal of Animal Nutri?tion, 2019, 31(6) :2701?2715]