Rumen Microbiota and Metabolome Reveal the Effects of Yucca schidigera Extract on Growth Performance and Serum Immune Parameters in Fattening Goats

This study aimed to investigate the effects of Yucca schidigera extract (YSE) on growth performance, serum immune parameters, rumen microbiota, and metabolites of fattening goats. For this purpose, thirty-two healthy male Boer goats with similar initial body weights (36.91 ± 3.05 kg) were randomly assigned to four groups. Goats in the control group (Group A) were fed a basal pelleted diet, whereas the experimental groups (Groups B, C, and D) received 200, 400, and 600 mg of YSE per kg of basal diet, respectively. The results reveal that dietary supplementation with 600 mg/kg YSE significantly elevated average daily gain (ADG) and decreased feed-to-gain ratio (F/G) (p < 0.05). The 400 mg/kg YSE addition significantly increased serum IgM concentration and reduced the TNF-α concentration (p < 0.05). Meanwhile, 400 mg/kg dietary YSE supplementation significantly elevated Ace and Chao-1 indices of ruminal microbiota (p < 0.05). Differential ruminal metabolites were predominantly enriched in pathways involving pantothenate and CoA biosynthesis, regulation of lipolysis in adipocytes, thermogenesis, and lysine degradation. Prevotellaceae_UCG-001 was negatively correlated with average daily feed intake (ADFI) and immunoglobulin M (IgM) (p < 0.05), and ascorbate radical and ureidoperacrylic acid showed significant correlations with ADFI, IgM, and Prevotellaceae_UCG-001 (p < 0.05). Both Anaerobispirillum and Quinella were negatively correlated with TNF-α (p < 0.05), whereas thiamine and zeatin showed positive correlations with TNF-α and Quinella (p < 0.05). Under the present experimental conditions, the optimal supplemental level of YSE was 400 mg/kg diet.