Effects of dietary lysozyme levels on growth performance, intestinal morphology, immunity response and microbiota community of growing pigs

BACKGROUND Lysozyme has been studied as a potential alternative to antibiotics for animals in recent years. The aim of this study was to evaluate the effect of dietary lysozyme on growth performance, serum biochemical parameters, immune response and gut health of growing pigs. RESULTS A total of 216 growing pigs (19.81 +/- 0.47 kg) were fed the diets supplemented with colistin sulfate at 20 mg kg(-1) (control), or lysozyme at 50 (L50) or 100 mg kg(-1) (L100) diet for 30 days. The results showed that pigs fed with L100 or control had greater average daily gain and gain-to-feed ratio than pigs in the L50 group. Pigs fed with L100 or colistin had greater villus height to crypt depth ratio in jejunum compared with pigs in the L50 group. Pigs fed with L100 had greater serum immunoglobulin A and jejunal secretory immunoglobulin A than control and L50, but lower serum total protein and globulin than control. No differences were observed in the messenger RNA expression of genes related to mucosal cytokines, antioxidant capacity, enzyme activity, and barrier functions among three treatments. The caecal microflora evenness was lower in the L100 group than in the control or L50 group by 16S ribosomal DNA sequencing. Phylogenetic investigation of communities by reconstruction of unobserved states analysis predicted that lysozyme may modify nutrient metabolism by changing intestinal microbial function of pigs. CONCLUSIONS Pigs supplemented with 100 mg kg(-1) lysozyme had similar growth performance and intestinal morphology as pigs fed with colistin. This was likely due to the improved systemic and gut immune responses and the reduced microbiota diversity by feeding 100 mg kg(-1) lysozyme. (c) 2018 Society of Chemical Industry