Repeated acidosis challenges and live yeast supplementation shape rumen microbiota and fermentations and modulate inflammatory status in sheep

Abstract

This study aimed to investigate the impact of repeated acidosis challenges (ACs) and the effect of live yeast supplementation (Saccharomyces cerevisiae I-1077, SC) on rumen fermentation, microbial ecosystem and inflammatory response. The experimental design involved two groups (SC, n = 6; Control, n = 6) of rumen fistulated wethers that were successively exposed to three ACs of 5 days each, preceded and followed by resting periods (RPs) of 23 days. AC diets consisted of 60% wheat-based concentrate and 40% hay, whereas RPs diets consisted of 20% concentrate and 80% hay. ACs induced changes in rumen fermentative parameters (pH, lactate and volatile fatty-acid concentrations and proportions) as well as in microbiota composition and diversity. The first challenge drove the fermentation pattern towards propionate. During successive challenges, rumen pH measures worsened in the control group and the fermentation profile was characterised by a higher butyrate proportion and changes in the microbiota. The first AC induced a strong release of rumen histamine and lipopolysaccharide that triggered the increase of acute-phase proteins in the plasma. This inflammatory status was maintained during all AC repetitions. Our study suggests that the response of sheep to an acidosis diet is greatly influenced by the feeding history of individuals. In live yeast-supplemented animals, the first AC was as drastic as in control sheep. However, during subsequent challenges, yeast supplementation contributed to stabilise fermentative parameters, promoted protozoal numbers and decreased lactate producing bacteria. At the systemic level, yeast helped normalising the inflammatory status of the animals.

Microbial fermentation of starch‑ or fibre‐rich feeds added with dry or pre‐activated Saccharomyces cerevisiae studied in vitro under conditions simulating high‐concentrate feeding for ruminants

“…The beneficial effect of S. cerevisiae on fibre fermentation (represented as sugar beet pulp) has been associated with an increase in rumen concentration of cellulolytic bacteria in mixed diets for sheep and buffaloes . Similarly, an increase of rumen concentration of Ruminococcus flavefaciens and Ruminococcus albus has been reported when live yeasts were supplemented to more than 50% concentrate diets for sheep . In contrast, our study showed a limited effect of added yeasts on fermentative activity of rumen bacteria with barley as substrate.…”

“…Anyway, the higher VFAs concentration with AY with respect to CT agrees with results from others and supports observed gas production results along the incubation period, although no treatment differences were recorded in molar VFAs proportions, suggesting that the effect of yeasts on fermentation is quantitative rather than qualitative. In this regard, some workers have reported increased proportions of propionate or butyrate in response to yeasts addition, but others did not observe any shift in the fermentation pattern …”

The Effect of Live Yeast Supplementation on Beef Cattle Performance: A Systematic Review and Meta-Analysis

“…This may be due to an increase in lactate-utilizing bacteria, Selenomonas ruminantium and Megasphaera elsdenii. These bacteria convert lactate to propionate (Lettat, Martin, Berger, & Nozière, 2012;Silberberg et al, 2013) and have their growth stimulated by the supplementation of yeast (Pinloche et al, 2013).…”

Nutraceuticals

“…The primary mechanisms of action are to stimulate total rumen bacterial population densities, shift or stabilize the balance of rumen bacterial populations, utilize lactic acid, and reduce the risk for ruminal acidosis, and maintain a low oxygen rumen environment. [78][79][80][81] Newbold and colleagues 78 designed well-controlled experiments to elucidate the mechanisms by which live yeast supplements may increase rumen bacterial population densities. Oxygen utilization by live yeast supplements seems to be an important mechanism improving the growth of rumen bacteria.…”