Effects of a dietary liquid extract of Lentinus edodes on the growth performance, immune traits, and intestinal flora of weaned Simmental calves

A high survival rate of calves is important to ensure the development of the cattle industry. The health of calves faces many challenges, and the low immunity of calves caused by weaning is the main cause of calf disease and death. However, excessive use of antibiotics is a key limitation to healthy breeding. This may be a problem for antibiotics prohibition due to the antibiotic growth promoter (AGP) residues. In this study, we evaluated the effects of the dietary liquid extract of Lentinus edodes ( L.E .) on the growth performance, blood immune indices, and intestinal flora of weaned Simmental calves. In total, 20 weaned Simmental calves (4 – 5 months old) with similar body conditions were randomly assigned to the control group or the experimental group (n = 10). The growth index, number of blood immune cells, and relative abundance of the intestinal flora were detected to evaluate the growth performance, immune traits, and changes in the intestinal flora of weaned calves after treatment with the L.E. extract for 60 days. The results indicated that the most effective strain was L808, with optimal fermentation at 28°C and a pH value of 6.5. The L.E. extract increased growth performance during the experimental period ( P < 0.05). Additionally, L.E. extract increased the levels of lymphocytes, neutrophils, white blood cells (WBC), immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), and the anti-inflammatory cytokines interleukin-2 (IL-2) and interleukin-10 (IL-10) (P < 0.05). However, the expression of serum tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) decreased after treatment with the L.E. extract ( P < 0.05). Furthermore, L.E. extract increased the relative abundances of the beneficial bacteria Firmicutes ( P = 0.030), Akkermansia ( P = 0.045), and norank_f__norank_o__Bacteroidales ( P = 0.020) and decreased the relative abundance of the harmful bacteria Escherichia-Shigella . To summarize, L.E. extract can enhance the growth performance, immune traits, and bacterial diversity of weaned calves, which may provide new insights into the application of L.E. for improving the production performance of weaned calves. • In this study, the optimal fermentation strain of Lentinula edodes L808 was screened out, along with the optimal culture conditions in the fermenter: the most suitable temperature is 28°C, and the optimal pH value is 6.5. • Lentinula edodes extract can increase the abundance of beneficial bacteria such as Firmicutes , Akkermansia , and Bacteroideae_norank_f__norank_o__Bacteroidales and decrease the abundance of harmful bacteria such as Escherichia-Shigella . • in this study, we evaluated the effects of Lentinula edodes extract on the growth performance, immune traits, and intestinal flora of weaned calves, thereby reducing the use of clinical antibiotics and providing new insights into the medical application of Lentinula edodes extract for weaned calves. • The liquid extract of Lentinus edodes mycelium has solved the problem of low immunity in beef calves during the weaning stage and the dilemma of avoiding the use of antibiotics, achieving healthy feeding.