Effects of rumen-protected arginine supplementation on the plasma amino acids and gut microbiota of sika deer (Cervus nippon)

Abstract

In this study, we examined the effects of rumen-protected arginine on antler growth, plasma biochemical values and the gut microbiota of sika deer (Cervus nippon). Twenty-four male sika deer were randomly allocated to one of four experimental diets: a basal diet with no arginine (CON, 0 g/day) or arginine supplementation groups that received 1 (LArg), 2 (MArg), or 3 (HArg) g/day of rumen-protected arginine. After an 8-week feeding trial, plasma metabolite levels were measured, and the faecal bacterial community was examined based on 16S rRNA gene sequencing. The final weight (P = 0.04) and daily gain of velvet antler (P = 0.04) in the HArg group were higher than those in the CON group. The glucose (P = 0.01) and triglyceride concentrations (P < 0.01) in plasma increased linearly, whereas the ALT (P = 0.01) and AST (P < 0.01) concentrations decreased linearly with the increase of arginine supplementation. In addition, the phosphoserine (P = 0.01), citrulline (P = 0.02), cystathionine (P = 0.01), ammonia (P = 0.01), and arginine (P = 0.01) levels increased linearly with the increase of arginine supplementation. Prevotella spp. were the dominant bacteria in the faeces of sika deer among the four groups. Principal coordinates analysis results showed that the bacterial communities and predicted functions of the CON group were different from those of the LArg, MArg and HArg groups based on the Bray-Curtis dissimilarity matrix (P < 0.01), unweighted UniFrac distance (P < 0.01), and weighted UniFrac distance (P < 0.01). The Firmicutes-to-Bacteroidetes ratios were higher (P < 0.01) in the arginine supplementation groups than that in the CON group. The relative abundances of Bacteroides spp., Rikenellaceae RC9, Treponema 2, Turicibacter spp., Romboutsia spp., Alistipes spp., and Phascolarctobacterium spp. were increased with dietary arginine supplementation, whereas the abundance of Prevotella spp. was decreased. Comparison of potential functions also showed enrichment of the fructose and mannose metabolism, pyruvate metabolism, propionate metabolism, and butyrate metabolism pathways. These results suggested that supplemental rumen-protected arginine affected sika deer metabolism and the gut microbiota.