Abstract

This study investigated the effects of composite postbiotic preparation on the growth performance, immune function, and microbiota composition of Nubian black goats. Thirty healthy Nubian black goats with similar body weights were randomly assigned to two groups (n = 15 per group): a control group fed a basal diet and a treatment group fed the basal diet supplemented with 0.5% composite postbiotic preparation (equal-ratio co-fermentation of Bacillus subtilis GX15 and Lentilactobacillus buchneri GX0328-6). The results indicated that while compound postbiotic supplementation did not significantly alter the average daily gain (ADG) and the serum biochemical indices (p > 0.05), it significantly increased the concentrations of immunoglobulins (IgG and IgA) compared to the control group (p < 0.05). Despite comparable α- and β-diversity, CPP supplementation selectively enriched Bacteroides, UCG-005, and Ruminococcaceae while reducing Turicibacter (LEfSe LDA > 2.0; STAMP p < 0.05), suggesting targeted modulation of gut microbiota. In conclusion, dietary supplementation with 0.5% composite postbiotic preparation improves immune function and modulates intestinal microbiota composition without significantly affecting growth performance in black goats while improving intestinal microbial composition and promoting overall gut health.