Rumen-protected lysine supplementation improved amino acid balance,nitrogen utilization and altered hindgut microbiota of dairy cows

This study was conducted to evaluate the effects of dietary crude protein(CP)and rumen-protected lysine(RPL)supplementation on lactation performance,amino acid(AA)balance,nitrogen(N)utilization and hindgut microbiota in dairy cows.Treatments were in a 2×2 factorial arrangement,and the main effects were CP concentration(16%vs.18%)and RPL supplementation(with or without RPL at40 g/cow per day).Forty cows were randomly allocated to 4 groups:low-CP diet(LP),low-CP diet plus RPL(LPL),high-CP diet(HP),high-CP diet plus RPL(HPL).The experiment was conducted for 8 weeks.Results showed that RPL increased the dry matter intake(P<0.01),milk protein yield(P=0.04)and energy corrected milk(P=0.04),and tended to increase milk fat yield(P=0.06)and fat corrected milk(P=0.05).Cows in the HP group tended to have higher milk urea N(P=0.07).Plasma concentrations of Arg,Ile,Lys,Met,Pro,total essential AA and total nonessential AA were increased by RPL(P<0.05).The total essential AA,total nonessential AA and most AA(except Ile,Phe,Gly and Pro)were increased in the HP group(P<0.05).N excretion was increased in the HP group through an increase in urea N excretion(P<0.01)and an upward trend in plasma urea N(P=0.07).In addition,RPL tended to increase milk protein N secretion(P=0.08),milk N(P=0.07)and microbial protein synthesis(P=0.06),and decreased plasma urea N(P<0.001).In the hindgut,the bacterial community were different between the LP and LPL groups(P<0.01).The probiotic abundances of Christensenellaceae_R-7_group and Acinetobacter were increased by RPL(P=0.03 and 0.03,respectively).The pathogenic abundances of Clostridium_sensu_stricto_1(P<0.001)and Turicibacter(P<0.01)were decreased by RPL.In conclusion,supplementing RPL with low dietary CP could balance AA supply and increase milk protein yield,resulting in an improvement in N utilization efficiency,and altered the composition of the hindgut microbiota to favor the lactation performance of dairy cows.

热应激条件下荷斯坦奶牛后段肠道差异微生物分析

本试验旨在分析热应激条件下,热应激耐受奶牛和热应激易感奶牛后段肠道菌群组成的差异,寻找与热应激相关的后段肠道微生物,为利用饲养管理和遗传选择等手段提高奶牛耐热能力提供理论依据。选择体况相近且健康的1胎中国荷斯坦泌奶牛19头,利用奶牛夏季上午直肠温度(MRT)和下午直肠温度(ART)差值(RTD)将其分为热应激易感组(H组,10头)和热应激耐受组(L组,9头)。采用Illumina PE250测序平台测定两组个体粪便中细菌16S rDNA V3~V4区序列,利用生物信息学方法筛选两组个体的差异微生物。结果表明:①L组的Shannon指数和Chao1指数高于H组,但组间差异不显著(P>0.05)。②在门水平,两组个体的厚壁菌门(Firmicutes)、拟杆菌门(Bacteroidetes)和变形菌门(Proteobacteria)的相对丰度之和均占总菌的95%以上;在属水平,L组中YRC 22和普雷沃氏菌属(Prevotella)的相对丰度显著高于H组(P<0.05),且YRC 22、Prevotella的相对丰度与ART、RTD、呼吸评分(RS)、直肠温度极值(RTR)及流涎评分(DS)等5项热应激相关指标均呈负相关关系。③与热应激相关的6项指标(MRT、ART、RTD、RS、DS、RTR)中,RS、DS和MRT在冗余分析(RDA)结果中R2较大,表明这3项指标与奶牛后段肠道微生物菌群相关程度较大。综上所述,热应激影响奶牛后段肠道菌群结构,Prevotella是热应激相关的后段肠道微生物。

低蛋白水平日粮添加复合酸化剂对断奶仔猪后肠微生物的影响

该试验旨在研究低蛋白水平日粮添加复合酸化剂对断奶仔猪后肠微生物菌群及其代谢组学的影响。选取体况相似、胎次相近的28日龄断奶的“杜洛克×长白×大白”三元杂交仔猪27头,随机分为3个组(每组3个重复,每个重复3头猪),对照组饲喂正常蛋白水平日粮(NP,粗蛋白20%),试验组分别饲喂中等蛋白水平日粮+复合酸化剂(MP+CA,粗蛋白18%,复合酸化剂8 g/kg)和低蛋白水平日粮+复合酸化剂(LP+CA,粗蛋白16%,复合酸化剂8 g/kg),试验期28 d。结果表明:(1)低蛋白水平日粮添加CA显著提高了结肠微生物群落的丰富度(P<0.05),对盲肠和结肠微生物群落多样性无显著影响(P>0.05);(2)门水平上,显著提高了后肠中厚壁菌门和拟杆菌门的相对丰度,降低了变形菌门的相对丰度(P<0.05);属水平上,显著提高了后肠中Syntrophococcus、Clostridium_sensu_stricto_1、Lachnospiraceae_NK4A136_group、Christensenellaceae_R_7_group和Ruminococcaceae_NK4A214_group等菌属的相对丰度,降低了Streptococcus和Escherichia-Shigella等菌属的相对丰度(P<0.05);(3)低蛋白水平日粮添加复合酸化剂显著影响了盲肠和结肠中的代谢物组成结构,主要影响了核黄素的代谢通路(P<0.05)。由此可见,低蛋白水平日粮添加复合酸化剂提高了仔猪后肠微生物菌群的丰富度和有益菌的相对丰度,降低了致病菌的相对丰度,改变了后肠中代谢物的组成和结构,引起后肠核黄素等代谢的改变,促进了仔猪肠道健康。

树鼩大肠内容物细菌的群落多样性分析

目的应用高通量测序技术分析树鼩大肠细菌的结构与组成。方法采集3只雄性树鼩大肠内容物,用细菌16Sr DNA通用引物扩增V3~V4区,采用Illumina PE250平台测序。结果共获得160 157条有效序列,聚类后得437个运算分类单位(operational taxonomic units,OTUs)。树鼩大肠中的细菌有9个门、19个纲、37个目、68个科、137个属和194个种。其中,(1)厚壁菌门和变形菌门的丰度最高,分别为63.30%和28.52%;(2)优势纲是芽孢杆菌纲和γ-变形菌纲(51.46%、28.02%);(3)乳杆菌目和肠杆菌目的丰度最高,为45.33%和27.51%;(4)优势科是乳杆菌科(35.30%)和肠杆菌科(27.51%);(5)乳杆菌属和埃希氏菌属为优势属(35.30%、27.49%);(6)在种的水平,可培养细菌的丰度为37.10%,未分类细菌27.69%,不可培养细菌35.21%。可培养细菌中,唾液链球菌的丰度最高(26.66%)。在丰度最高的20个种中,8种细菌(40%)未分类,为以往未被发现的新种。个体间细菌群落存在一定差异。结论树鼩大肠内容物中的细菌组成具有丰富的多样性,其中还有许多未被分类鉴定且相对丰度较高的细菌,需要进一步研究。