Effects of dietary inclusion of Xanthoceras sorbifolia Bunge leaves on growth performance, gastrointestinal development, digestive function and gut microbial flora of rabbits

This study aimed to investigate the effects of dietary inclusion of Xanthoceras sorbifolia Bunge (X sorbifolia) leaves (XSL) or solid-state fermented X sorbifolia leaves (FXSL) on the growth performance, gastrointestinal tract development, serum metabolites, intestinal mucosa morphology, cecal fermentation and microflora enumeration of rabbits. A total of 192 healthy New Zealand White male rabbits weighing (940 ± 11 g) were randomly allocated to 3 dietary treatments, with 8 replicates of 8 rabbits each and designated as control, XSL, and FXSL groups. The rabbits in the XSL and FXSL groups were fed diets containing 150 g/kg XSL and FXSL in the basal diets to replace the same level of alfalfa hay, respectively for 42 days. Compared with the control or XSL group, the FXSL rabbits showed increased average daily weight gain (P < 0.05) and final body weight, as well as a decreased feed to gain ratio (P < 0.05). They had increased small intestine weight, small intestine relative weight (P < 0.05), cecum weight, cecum relative weight, and decreased urea nitrogen (UN) content (P < 0.05). Rabbits in the XSL and FXSL groups had lower serum alanine aminotransferase (ALT) (P < 0.05) and aspartate aminotransferase (AST) activities, as well as higher serum alkaline phosphatase (AKP) activity (P < 0.05). Compared to the other two groups, the total volatile fatty acids, the ratio of acetic acid, as well as Lactobacilli and Bifidobacterium populations in the cecal content was increased (P < 0.05) in the FXSL group, while the cecal pH, NH3-N, the ratio of butyric acid, Escherichia coli as well as Clostridium perfringens populations were decreased (P < 0.05). Further, the rabbits from the FXSL group showed higher (P < 0.05) villus height (VH) and VH/crypt depth (CD) both in the jejunum and duodenum. In conclusion, adding 150 g/kg XSL to the diet can replace the same amount of alfalfa powder, simultaneously, adding 150 g/kg FXSL can improve the growth and gastrointestinal tract development, as well as the cecal environment and microbiota balance.