Abstract
Subacute ruminal acidosis (SARA) is often caused by feeding a high-concentrate diet in intensive ruminant production. Although previous studies have shown that dietary thiamine supplementation can effectively increase rumen pH and modify rumen fermentation, the effect of thiamine supplementation on rumen carbohydrate-related microorganisms and enzymes in goats under SARA conditions remain unclear. Therefore, the objective of the present study was to investigate the effects of dietary thiamine supplementation on carbohydrate-associated microorganisms and enzymes in the rumen of Saanen goats fed high-concentrate diets. Nine healthy mid-lactating Saanen goats in parity 1 or 2 were randomly assigned into three treatments: A control diet (CON; concentrate:forage (30:70)), a high-concentrate diet (HC; concentrate:forage (70:30)), and a high-concentrate diet with 200 mg of thiamine/kg of DMI (HCT; concentrate:forage (70:30)). Compared with the HC group, dietary thiamine supplementation improved ruminal microbes associated with fiber, including Prevotella, Fibrobacter, Neocallimastix, and Piromyces (p < 0.05). In addition, an increase in the relative abundance of enzymes involved in both fiber degradation and starch degradation, such as CBM16, GH3, and GH97, was observed in the HCT treatment. (p < 0.05). Thus, thiamine supplementation can improve carbohydrate metabolism by increasing the abundance of the microorganisms and enzymes involved in carbohydrate degradation. In conclusion, this study revealed the relationship between ruminal microbiota and enzymes, and these findings contributed to solving the problems arising from the high-concentrate feeding in ruminant production and to providing a new perspective on ruminant health.
Highlights
IntroductionDietary carbohydrates play an important role in ruminant nutrition and their digestive and physiological functions and most of the carbohydrates ingested are eventually converted into volatile fatty acids (VFAs) by ruminal microorganisms
We found that the starch-related decomposers were affected differently by high-concentrate diets, which decreased the relative abundance of Bifidobacterium and Bacteroides and increased the relative abundance of Succinimonas, Anaerovibrio, Veillonella, and Lactobacillus
We found that high-concentrate diets decreased the relative abundance of starch-degrading enzymes, including GH97 and GH13, which is consistent with previous studies [34,47]
Summary
Dietary carbohydrates play an important role in ruminant nutrition and their digestive and physiological functions and most of the carbohydrates ingested are eventually converted into volatile fatty acids (VFAs) by ruminal microorganisms. These VFAs are the main energy precursors for ruminants, and can meet approximately 70% of their caloric requirements [1]. Fibrous materials and starch are two typical carbohydrates in the diet of ruminants, wherein the fiber mainly consists of cellulose, hemicellulose, and lignin. Rumen microorganisms produce various carbohydrate-degrading enzymes, which convert cellulose, hemicellulose, and starch into disaccharides and further convert them into
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