<scp>d</scp>-Aspartate in Low-Protein Diets Improves the Pork Quality by Regulating Energy and Lipid Metabolism via the Gut Microbes

Abstract

d -Aspartate is critical in maintaining hormone secretion and reproductive development in mammals. This study investigated the mechanism of different d -aspartate levels (0, 0.005, 0.05, and 0.5% d -aspartate) in low-protein diets on growth performance and meat quality by mediating the gut microbiota alteration in pigs. We found that adding 0.005% d -aspartate to a low-protein diet could dramatically improve the growth performance during the weaned and growing periods. Dietary d -aspartate with different levels markedly increased the back fat, and 0.5% d -aspartate significantly increased the redness in 24 h and reduced the shear force of the longissimus dorsi (LD) muscle. Moreover, d -aspartate treatments decreased the mRNA expression of MyHC II a and MyHC IIx in the LD muscle. The protein expression of MyH1, MyH7, TFAM, FOXO1, CAR, UCP2, and p-AMPK was upregulated by 0.005% d -aspartate. Additionally, the abundance of Alistipes, Akkermansia, and the [ Eubacterium ]_ coprostanoligenes _group in the intestinal chyme of pigs was significantly decreased by d -aspartate treatments at the genus level, which was also accompanied by a significant decrease in acetate content. These differential microorganisms were significantly correlated with meat quality characteristics. These results indicated that d -aspartate in low-protein diets could improve the growth performance and meat quality in pigs by regulating energy and lipid metabolism via the alteration of gut microbiota.