Feeding live yeast (Saccharomyces cerevisiae) improved performance of mid-lactation dairy cows by altering ruminal bacterial communities and functions of serum antioxidation and immune responses

Abstract

Background: The utilization of live yeast (Saccharomyces cerevisiae, YE) in dairy cows is gaining traction in dairy production as a potential strategy to improve feed efficiency and milk yield. However, the effects of YE on dairy cow performance remain inconsistent across studies, leaving the underlying mechanisms unclear. Hence, the primary aim of this study was to investigate the impact of YE supplementation on lactation performance, ruminal microbiota composition and fermentation patterns, as well as serum antioxidant capacity and immune functions in dairy cows.

Results: Supplementation with YE (20 g/d/head) resulted in enhancements in dairy cow's dry matter intake (DMI) (P = 0.016), as well as increased yields of milk (P = 0.002) and its components, including solids (P = 0.003), fat (P = 0.014), protein (P = 0.002), and lactose (P = 0.001) yields. The addition of YE led to significant increases in the concentrations of ammonia nitrogen (NH₃-N) (P = 0.023), acetate (P = 0.005), propionate (P = 0.025), valerate (P = 0.003), and total volatile fatty acids (VFAs) (P < 0.001) in rumen fermentation parameters. The analysis of 16s rRNA gene sequencing data revealed that the administration of YE resulted in a rise in the relative abundances of three primary genera including Ruminococcus_2 (P = 0.010), Rikenellaceae_RC9_gut_group (P = 0.009), and Ruminococcaceae_NK4A214_group (P = 0.054) at the genus level. Furthermore, this increase was accompanied with an enriched pathway related to amino acid metabolism. Additionally, enhanced serum antioxidative (P < 0.05) and immune functionalities (P < 0.05) were also observed in the YE group.

Conclusions: In addition to improving milk performance, YE supplementation also induced changes in ruminal bacterial community composition and fermentation, while enhancing serum antioxidative and immunological responses during the mid-lactation stage. These findings suggest that YE may exert beneficial effects on both rumen and blood metabolism in mid-lactation dairy cows.

Keywords: Saccharomyces cerevisiae; Animal health; Lactation performance; Ruminal microbiota-host interaction.

Fig. 1

Effects of live yeast (YE) on ruminal microbiota of dairy cows. (A), (B), (C), and (D) The richness and diversity indices of rumen microbiota in dairy cows fed basal (CON) or live yeast (YE) diet. (E) Principal coordinate analysis (PCoA) of the overall rumen microbiota in dairy cows based on unweighted UniFrac distance

Fig. 2

Effects of live yeast (YE) on the rumen bacterial composition at the phylum (A), family (B), and genus (C) levels in dairy cows. “*”, “**”, and “***” indicate the significance level at 0.05, 0.01 and 0.001, respectively

Fig. 3

LEFse (Liner discriminant analysis Effect Size) cladogram comparing microbiota communities between the YE and CON groups. Differences are represented by colour, indicating the group where taxa are most abundant: red = taxa abundant in the basal (CON) group, blue = tax abundant in the live yeast (YE) group

Fig. 4

Correlation between the relative abundances of rumen bacteria, lactation performance (A), and fermentation parameters (B). “*”, “**”, and “***” indicate the significance level at 0.05, 0.01 and 0.001, respectively

Fig. 5

Functional prediction of bacterial populations in ruminal samples of dairy cows fed the basal (CON) or live yeast (YE) diet. Prediction of the differential function of rumen microbes between two groups of dairy cows in Kyoto Encyclopaedia of Genes and Genomes (KEGG) level 2 category based on PICRUSt 2. “*”, “**”, and “***” indicate the significance level at 0.05, 0.01 and 0.001, respectively