Effects of Diets with Different Energy Levels on Rumen Fermentation Characteristics and Microbial Composition of Weaned Male Shaanbei White Cashmere Goats
This experiment was conducted to investigate the effects of dietary energy level on rumen fermentation characteristics and microbial composition of weaned male Shaanbei white cashmere goats.A total of 40 healthy Shaanbei white cashmere goats with similar body weight(approximate(13.80±1.60)kg)were selected and randomly divided into 4 groups(Ⅰ,Ⅱ,Ⅲ andⅣ).The crude protein(CP)level was 11.8％,and group Ⅰ,Ⅱ,Ⅲ and Ⅳ were fed four diets with different digestible energy(DE)of 9.16,9.66,10.16 and 10.66 MJ·kg-1,respectively.The feeding experiment lasted for 60 days,including 7 days of pre-experiment and 53 days of formal experiment.At the end of experiment,rumen fluid was collected to investigate rumen fermentation parameters,and total DNA was extracted from rumen fluid.After PCR amplification,high-throughput sequencing and analysis were performed on the V3-V4 regions of 16S rRNA to study the rumen microbial composition.The results were showed as follows:1)As the energy level increasing,pH,ammonia nitrogen(NH3-N)content,and acetate to propionate ratio of rumen fluid decreased gradually.Total volatile fatty acid,acetate,and propionate content showed a trend of first increasing and then decreasing,while microbial crude protein(MCP)concentrations,butyrate and valerate content gradually increased;The pH of group Ⅳ was significantly lower than the other three groups(P＜0.05),the propionate in group Ⅰ was significantly lower than that in groups Ⅲ and Ⅳ(P＜0.05),and the acetate to propionate ratio ingroup Ⅰ was extremely significantly higher than that in groups Ⅲ and Ⅳ(P＜0.01).2)Rumen microbial alpha diversity showed that with the increase of dietary energy levels,the Shannon and Simpson indices gradually decreased,while Chao1、faith_pd and observed_OTUs index showed a trend of first increasing and then decreasing,with Chao1 and observed_OTUs index in groups Ⅰ and Ⅱ were significantly higher than that of groups Ⅲ and Ⅳ(P＜0.05).3)The analysis of rumen microbial community composition showed that the dominant bacterial phyla included Bacteroidetes and Firmicutes,followed by Proteobacteria;With the energy level increasing,the relative abundance of Bacteroidea gradually decreased,while the relative abundance of Firmicutes and Proteobacteria gradually increased;The dominant bacterial genera were Prevotella and Ruminococcus,with the energy level increasing,the relative abundance of Prevotella gradually decreased,while the abundance of Ruminococcus significantly increased.4)The analysis of differential abundance comparison of rumen microbiota showed that:At the phylum level,the relative abundance of Proteobacteria in group Ⅳ was the highest and significantly higher than that of the other three groups(P＜0.05).The relative abundance of TM7 in group Ⅱ and Ⅲ was significantly higher than that in groups Ⅰ and Ⅳ(P＜0.05),while the relative abundance of Synergistetes in group Ⅰ was significantly higher than that in the other three groups(P＜0.05).At the genus level,the relative abundance of Ruminococcus in group Ⅰwas extremely significantly lower than that of the other three groups(P＜0.01),while the relative abundance of Oscillospira in groups Ⅰ and Ⅱ were extremely significantly lower than that of groups Ⅲ and Ⅳ(P＜0.01).The relative abundance of Unspecified Bacteroides in groups Ⅰand Ⅲ was significantly higher than that of groups Ⅱ and Ⅳ(P＜0.05),the relative abundance of Succinomycetes,Unspecified Veillonellaceae,Unspecified Lachnospiraceae,and Unspecified Clostridials in groups Ⅰ and Ⅱ were all significantly higher than that of groups Ⅲ and Ⅳ(P＜0.05),the relative abundance of Unspecified_RF32 in groups Ⅱ and Ⅳ was significantly higher than that of groups Ⅰ and Ⅲ(P＜0.05),and the relative abundance of Unspecified_F 16 in groupⅡ and Ⅳ was significantly higher than that of groups Ⅰ and Ⅳ(P＜0.05).In conclusion,the increased dietary energy level affected the rumen fermentation characteristics of weaned male Shaanbei white cashmere goats,with a trend towards reducing the richness of rumen bacteria,as well as significantly changed the relative abundance of Proteobacteria,Synergites,Ruminococcus and Succinococcus.And the diet with digestible energy level of 9.66 MJ·kg-1 can effectively improve the rumen fermentation characteristics and bacterial composition of weaned male Shaanbei white cashmere goats.
Shaanbei white cashmere goatsweaned male goatsenergy levelrumen fermentation characteristicscomposition of rumen microbiota
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