Effects of L-arginine supplementation on fat deposition and meat quality in growing lambs: Interactions with gut microbiota and metabolic signalling pathways.

Arginine (ARG) improves meat quality and fat deposition; however, its effects on gut microbiota-mediated lipid metabolism in lambs remain unclear. Twenty-four lambs were divided into control (fed a basal diet) and ARG groups (with 1 % ARG added). In the ARG group, backfat thickness, shear force in the longissimus thoracis (LT) muscle, and C16:0 and SFA contents in the subcutaneous adipose tissue (SAT) were reduced, whereas the eye muscle area, a* value, and intramuscular fat, C18:2n-6c, C20:4n-6, C20:5n-3, and PUFA contents in the LT were elevated. Moreover, the ARG group exhibited higher levels of Prevotella, Akkermansia, Faecalibacterium, SCFAs, and GLP-1 in the colon, and lower serum triglyceride and glucose levels. Interestingly, ARG differentially regulated lipid metabolism in the SAT and LT via the GLP-1R/AMPK and triglyceride metabolism signalling pathways. Overall, ARG addition may optimise gut microbiota composition, fat deposition, and meat quality, providing application guidance for regulating fat deposition in lambs.