# Effects of rumen-protected lysine on antler growth performance, fecal bacterial community, and blood gene expression in sika deer

## TL;DR

This study shows that adding rumen-protected lysine to sika deer diets improves antler growth and affects gut bacteria and gene activity.

## Contribution

The study reveals new insights into how lysine affects antler growth and gut microbiota in sika deer.

## Key findings

- Rumen-protected lysine increased antler weight and nutrient digestibility in sika deer.
- Lysine altered fecal bacterial communities, increasing Fibrobacter and decreasing other species.
- Lysine influenced gene expression, affecting pathways like MAPK and p53 signaling.

## Abstract

Velvet antler is an important product of sika deer (Cervus nippon), and its growth is closely related to dietary amino acid supplementation. Lysine is one of the major limiting amino acids in animals; however, the mechanism underlying its effect on velvet antler growth in sika deer remains unclear.

This study investigated the impact of rumen-protected lysine supplementation on velvet antler growth, nutrient digestibility, gut bacteria, serum biochemical parameters, and gene expression in sika deer. Fifteen healthy 2-year-old male sika deer were randomly assigned to three dietary groups: control (0 g/day rumen-protected lysine, CON), low (5 g/day rumen-protected-lysine, LLys), and high (10g/day rumen-protected lysine, HLys).

Supplementation with rumen-protected lysine significantly increased antler weight and dry matter, crude protein, neutral detergent fiber, and acid detergent fiber digestibility (P < 0.05). The concentrations of acetate and propionate in the feces of the LLys were significantly higher than those in the CON (P < 0.05). The relative abundance of Fibrobacter in the feces was significantly higher in the HLys group compared to the CON group (P < 0.05). The relative abundance of Papillibacter, Coprococcus, Anaerorhabdus furcosa, and Parabacteroides were significantly lower in the HLys than in the CON (P < 0.05). The gene expression was influenced in both HLys and LLys groups compared to the CON group, with upregulated dierentially expressed genes (DEGs) and downregulated DEGs identified. KEGG pathway analysis showed upregulated DEGs were enriched in MAPK, PI3K-Akt, TNF, p53, FoxO, JAK-STAT, NF-κB, and Toll like receptor signaling pathways. Down regulated DEGs were enriched in glutathione metabolism, lysine degradation, fatty acid elongation, biosynthesis of unsaturated fatty acids, Th17 and Th2 cell differentiation.

Overall, these results provide novel insights into the effect of rumen-protected lysine supplementation on antler growth, host digestibility and metabolism, fecal microbiota, and blood transcriptome of sikadeer.