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

Abstract

Objective: 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.

Methods: 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: Results showed that goats' final weight (FW) and average daily gain (ADG) significantly increased in the GAS group compared to the CON group (p < 0.05). The GAS group exhibited enhanced activities of total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and higher total antioxidant capacity (T-AOC) levels, while malondialdehyde (MDA) content significantly decreased (p < 0.05). Immunoglobulin A (IgA) and immunoglobulin G (IgG) levels were significantly elevated, along with increased concentrations of anti-inflammatory cytokines interleukin-4 (IL-4) and interleukin-10 (IL-10), whereas pro-inflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-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, while 21-deoxycortisol negatively affected metabolic balance.

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