Abstract
BACKGROUNDClimatic and dietary shifts predispose ruminal microbes to hyperthermal and hyperosmotic stress, leading to poor fermentation and subsequently adverse effects on ruminant productivity. Betaine may function as substrate, osmolyte, antioxidant, and methyl donor for microbes. However, its effect depends on the extent of microbial catabolism. This study revealed the ruminal disappearance kinetics of betaine and its dose effect on ruminal fermentation during thermal and osmotic stress using a rumen simulation technique.RESULTSThree different betaine doses were used: 0, 50, and 286 mg L−1; each was assigned to two incubation temperatures (39.5 and 42 °C) and two osmotic conditions (295 and 420 mOsmol kg−1). Betaine disappeared rapidly within the first 6 h of incubation; however, the rate was lower during hyperosmotic stress (P < 0.05), the stress condition that also suppressed the overall fermentation and degradation of organic nutrients and decreased the bacterial diversity (P < 0.001). During hyperosmotic stress, betaine shifted the fermentation pathway to more propionate (P < 0.05). Betaine counteracted the negative effect of hyperthermal stress on total short‐chain fatty acid concentration (P < 0.05) without affecting the composition. Both stress conditions shifted the bacterial composition, but the effect of betaine was minimal.CONCLUSIONDespite its rapid ruminal disappearance, betaine modulated microbial fermentation in different ways depending on stress conditions, indicating the plasticity of the betaine effect in response to various kinds of physicochemical stress. Although betaine did not affect the abundance of ruminal microbiota, the enhanced fermentation suggests an improved microbial metabolic activity under stress conditions. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Highlights
Ruminants are dependent upon ruminal microbes, which enable many biochemical functions, such as formation of short-chain fatty acids (SCFAs) and microbial protein synthesis by fermenting feedstuffs that are typically not digested by the host.[1]
The addition of betaine in the rumen could be of high significance to the animal because betaine, as a substrate and methyl donor for microbes, directly modulates ruminal fermentation[23,38] and, as a compatible osmolyte, betaine may enable the microbial tolerance to stressors.[39]
Betaine was rapidly degraded by ruminal microbiota in vitro, but the degradation was delayed during hyperosmotic stress, the stress condition that largely compromised overall degradation of major nutrients and shifted the fermentation pathway to more propionate
Summary
Ruminants are dependent upon ruminal microbes, which enable many biochemical functions, such as formation of short-chain fatty acids (SCFAs) and microbial protein synthesis by fermenting feedstuffs that are typically not digested by the host.[1]. As a result of such physicochemical changes, the metabolism and growth of ruminal microbes are placed under stress, which, depending on the severity, can compromise the stability of the rumen ecosystem and animal health. Since diet is the largest determining factor of rumen microbial stability,[11] diet fortification would be the most promising way to rectify the effects of physicochemical challenges to ruminal. This study revealed the ruminal disappearance kinetics of betaine and its dose effect on ruminal fermentation during thermal and osmotic stress using a rumen simulation technique
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