Enhancing Sheep Rumen Function, and Growth Performance Through Yeast Culture and Oxalic Acid Supplementation in a...

Yeast culture (YC) is a microbial product that enhances ruminal fiber breakdown and improves nutrient digestion and utilization. Our previous research showed that oxalic acid (OA) is a crucial metabolite in YC that enhances rumen function. This study aimed to investigate the effects of YC, OA, and their combination (YO) on rumen function, growth, and fattening in sheep. Twenty lambs were divided into 4 groups (ctrl, YC, OA, and YO; n = 5 each) and fed a diet supplemented with 2 levels of YC and 2 doses of OA for 60 days in a 2 × 2 factorial design. Growth and fattening performance, rumen microbiome analysis, serum indices and anti-oxidant levels, and metabolomic profiling were performed. Individual supplementation with YC and OA significantly increased the digestibility of dry matter (DM), organic matter (OM), and crude protein (CP) (p < 0.001); neutral detergent fiber (NDF) (p < 0.05); and acid detergent fiber (ADF) (p < 0.001) and their interaction significantly increased dry matter intake (DMI) (p = 0.05). Serum IgA and IgM levels were higher in the supplemented groups (p < 0.05). Serum calcium levels were higher in the OA and YO groups (p < 0.001). The supplemented groups showed significantly higher growth hormone and superoxide dismutase levels (p < 0.05). The longissimus dorsi muscle had higher levels of iron in the OA and YO groups; zinc in the OA, YO, and YC groups (p < 0.01); and selenium in the YC group (p < 0.05). The OA group had a higher total antioxidant capacity. All supplemented groups showed higher bacterial richness and diversity. Ruminococcus, Succinivibrio, and Fibrobacter were positively correlated with the fermentation and digestibility parameters. The supplementation also altered metabolite levels and types in key physiological pathways. In conclusion, this supplementation improved bacterial composition, nutrient digestibility, weight gain, carcass weight and quality, serum indices, antioxidant levels and metabolomic profiles. This suggests potential for the development of dietary supplements for ruminants.