Evaluation of garlic skin as a forage source for goats: effects on performance, antioxidant capacity, immune function...

This study aimed to evaluate the effects of garlic skin as a feed ingredient on growth performance, antioxidant capacity, immune function, and rumen health in goats.

Twelve male black goats with similar body conditions were randomly assigned to two groups. The control group (CON) was fed a basal diet, while the experimental group (GAS) received a diet supplemented with garlic skin for 60 days.

Results showed that goats' final weight and average daily gain significantly increased in the GAS group compared to the CON group (p<0.05). The GAS group exhibited enhanced activities of total superoxide dismutase, glutathione peroxidase, catalase, and higher total antioxidant capacity levels, while malondialdehyde content significantly decreased (p<0.05). Immunoglobulin A and immunoglobulin G levels were significantly elevated, along with increased concentrations of anti-inflammatory cytokines interleukin-4 and interleukin-10, whereas pro-inflammatory cytokines interleukin-1β, interleukin-6, and tumor necrosis factor-α were significantly reduced (p<0.05). The rumen fluid of GAS group showed significant increases in ammonia nitrogen, acetate, propionate, and total volatile fatty acids, with a reduction in the acetate-to-propionate ratio (p<0.05). Significant improvements were also observed in rumen papilla height, width, and density (p<0.05). 16S rDNA analysis revealed enhanced microbial diversity and enrichment of functional bacterial groups, such as Firmicutes and Christensenellaceae_R-7_group, involved in fiber degradation and volatile fatty acid production. Key metabolites, including 5-methylthioribose and glucose 6-phosphate, were positively correlated with growth and antioxidant capacity.

In conclusion, garlic skin supplementation enhanced antioxidant and immune function, optimized rumen fermentation, improved microbial composition, and promoted goat health and productivity.