Effects of Rumen-Protected Lysine on Antler Growth Performance, Fecal Bacterial Community, and Blood Gene Expression in Sika Deer

Bo Yang¹Yuhang Zhu¹Yongxiang Li¹Yating Gao¹Huazhe Si^1*Zhi Peng Li^1,2,3,4*

• ¹Jilin Agriculture University, Changchun, China
• ²Modern Agricultural Technology International Cooperative Joint Laboratory of the Ministry of Education, Jilin Agriculture University, Changchun, Hebei Province, China
• ³Jilin Provincial Engineering Research Center for Efficient Breeding and Product Development of Sika Deer, Jilin Agricultural University, Changchun, China
• ⁴Key Laboratory of Animal Production, Product Quality and Security, Ministry of Education, Jilin Agricultural University, Chuangchun, China

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 (10 g/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 580 upregulated differentially expressed genes (DEGs) and 652 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. Downregulated DEGs were enriched in glutathione metabolism, lysine degradation, fatty acid elongation, biosynthesis of unsaturated fatty acids, Th1 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 sika deer.