Comparative effects of enzymatic soybean, fish meal and milk powder in diets on growth performance, immunological parameters, SCFAs production and gut microbiome of weaned piglets

BACKGROUND: The objective of this study was to evaluate the replacement effects of milk powder (MK) and fish meal (FM) by enzymatic soybean (ESB) in diets on growth performance, immunological parameters, SCFAs production and gut microbiome of weaned piglets. METHODS: A total of 128 piglets with initial body weight at 6.95 ± 0.46 kg, were randomly assigned into 4 dietary treatments with 8 replicates per treatment and 4 piglets per replicate for a period of 14 d. Piglets were offered iso-nitrogenous and iso-energetic diets as follows: CON diet with MK and FM as high quality protein sources, ESB plus FM diet with ESB replacing MK, ESB plus MK diet with ESB replacing FM, and ESB diet with ESB replacing both MK and FM. RESULTS: No significant differences were observed in growth performance among all treatments (P > 0.05). However, piglets fed ESB plus FM or ESB diet had increased diarrhea index (P<0.01), and lower digestibility of dry matter (DM), gross energy (GE) or crude protein (CP), relative to piglets fed CON diet (P < 0.01). Moreover, the inclusion of ESB in diet markedly decreased the plasma concentration of HPT and fecal concentration of butyric acid (BA) (P<0.01). The High-throughput sequencing of 16S rRNA gene V3−V4 region of gut microbiome revealed that the inclusion of ESB in diet increased the alpha diversity, and the linear discriminant analysis effect size (LEfSe) showed that piglets fed with ESB plus FM or ESB diet contained more gut pathogenic bacteria, such as g_Peptococcus, g_Veillonella and g_Helicobacter. CONCLUSION: The inclusion of ESB in diet did not markedly affect growth performance of piglets, but the replacement of MK or both MK and FM by ESB increased diarrhea index, which could be associated with lower nutrients digestibility and more gut pathogenic bacteria. However, piglets fed diet using ESB to replace FM did not markedly affect gut health-related parameters, indicating the potential for replacing FM with ESB in weaning diet.