Metagenomic Analyses of Microbial and Carbohydrate-Active Enzymes in the Rumen of Dairy Goats Fed Different Rumen Degradable Starch

Abstract

The objective of this study was to investigate the effects of different dietary rumen degradable starch (RDS) on the diversity of carbohydrate-active enzymes (CAZymes) and Kyoto Encyclopedia of Genes and Genomes Orthology functional categories to explore carbohydrate degradation in dairy goats. Eighteen dairy goats (second lactation, 45.8 ± 1.54 kg) were divided in three groups fed low RDS (LRDS), medium RDS (MRDS), and high RDS (HRDS) diets. The results showed that, HRDS treatment group significantly decreased the ruminal pH (P < 0.05), and increased the propionate proportion (P < 0.05), fumarate and succinate concentrations (P < 0.05), trended to increase lactate concentration (P = 0.50) compared with LRDS group. The relative abundance of acetogens, such as family Clostridiaceae and Ruminococcaceae, genera Clostridium and Blautia were higher in HRDS than LRDS feeding goats. The GH9 family (responsible for cellulose degradation) genes were lower in HRDS than MRDS diet samples, and mainly produced by Prevotellaceae, Ruminococcaceae, and Bacteroidaceae. Amylose (EC3.2.1.3) genes under HRDS treatment were more abundant than under LRDS treatment. However, the abundance of GH13_9 and CBM48 (responsible for starch degradation) were reduced in HRDS group indicating the decreased binding activity from catalytic modules to starch. This study revealed that HRDS-fed dairy goats had decreased CAZymes, which encode enzymes degrade cellulose and starch in the dairy goats.

Real-time monitoring of ruminal microbiota reveals their roles in dairy goats during subacute ruminal acidosis

“…There were significant differences in the rumen fermentation parameters between the healthy group and the SARA group in this experiment. Previous studies have shown that the fermentation of high-concentration diets increases the proportion of propionate in the rumen, and decreases the proportion of acetate and the ratio of acetate to propionate; the fermentation of low-concentration diets can increase the proportion of acetate 8 , 16 , which is consistent with the results of this study. Doepel et al 26 reported that the T-VFA concentration increased with the proportion of dietary wheat, and the change in the rumen pH was highly inversely related to the VFA concentration.…”

“…Most of the existing studies on rumen microorganisms are based on analyses of the correlations between the microbial flora and host phenotype, and there is no corresponding model animal to reveal the symbiotic relationship and causality between ruminal microorganisms and the symptom in ruminants during SARA [13][14][15][16] . By using model animals such as Drosophila, mice, zebrafish, etc., numerous studies have focused on the function of gastrointestinal microbiota and have revealed the causality between microbiota and their hosts [17][18][19] .…”

A Metagenomic Insight Into the Hindgut Microbiota and Their Metabolites for Dairy Goats Fed Different Rumen Degradable Starch

“…We have found that RDS can be used as an effective measurement of dietary carbohydrate and digestive health in ruminants ( Shen et al, 2020b ). As the RDS level increased, more starch would be degraded in rumen and less starch would reach the intestine when the three treatment diets were formulated to be an isostarch ( Li et al, 2014c ).…”

“…However, no difference in pH level was found in any segments of intestine we detected, and no animals had diarrhea or other digestive problems, suggesting that rumen acid accumulation and inflammation induced by systemic entry of endotoxins did not cause observable hindgut acidosis in the HRDS group. Our previous study shown that HRDS altered the compositions of volatile fatty acid (VFAs) in rumen ( Shen et al, 2020b ). For ruminants, the fermentation site (rumen and hindgut) producing VFAs is more diverse than monogastric animals ( Jin et al, 2018 ).…”

“…Due to the complex and abundant microorganisms colonized in the rumen and cecum, feed fermentation organs in ruminants are more diverse than monogastric animals ( Howie and Baker, 1952 ; Shen et al, 2020b ). Rumen has attracted a tremendous amount of attention in ruminant nutrition studies, whereas limited attention has been placed on the microorganism of the hindgut ( Seshadri et al, 2018 ; Xue et al, 2020 ).…”