Effects of Enzyme–Microbe Co-fermented Ganoderma Lucidum Spent Substrate on Growth Performance, Apparent Nutrient Digestibility, Organ Indices, and Gut Microbiota in Yellow-Feathered Broilers

This study investigated the effects of dietary supplementation with different levels of enzyme–microbe co-fermented Ganoderma lucidum spent substrate (EFGLS) on growth performance, apparent nutrient digestibility, organ indices, and cecal microbi-ota in yellow-feathered broilers. A total of 450 healthy broilers (22 days of age) with similar body weight were randomly assigned to three dietary treatments, with five replicates per treatment and 30 birds per replicate. The control group was fed a corn–soybean meal–based basal diet, while the experimental groups received diets supple-mented with 1.5% or 3.0% fermented G. lucidum spent substrate to partially replace corn and soybean meal. The feeding trial lasted for 6 weeks. The results showed that: (1) over the entire experimental period, broilers fed diets containing 1.5% or 3.0% EFGLS exhibited significantly greater average daily gain (ADG) and a markedly lower feed-to-gain ratio (F/G) compared with the control group (p < 0.001); (2) apparent nu-trient digestibility tended to increase in both EFGLS–supplemented groups, although no significant differences were observed (p > 0.05); (3) the thymus index was signifi-cantly higher in the 1.5% supplementation group than in the 3.0% group (p < 0.05); and (4) the Pielou’s evenness, Shannon, and Simpson indices of the cecal microbiota were significantly higher in the 3.0% group than in the control group (p < 0.05), whereas the Dominance index was significantly higher in the control group than in both experi-mental groups.