Effects of Early-Life Exposure to Topsoil on the Muscle Fiber Characteristics and Gene Expression of Weaned Piglets

Abstract

\n Background: The objective of this experiment was to investigate the influence of early exposure to topsoil on the muscle fiber characteristics and transcription related myogenesis, intramuscular fat metabolism, muscle fiber types, and mTOR signaling pathway of weaned pigs.Methods: A Total of 180 piglets were separately assigned to No soil, Antibacterial soil, and Normal soil group (each group, n=60), and were fed ad libitum with common antibiotic-free corn-soybean meal diets until day-31. Ten pigs from each group with similar body weight were selected to be slaughtered, and the longissimus dorsi (LD) muscle samples were collected for histological analysis and measurements of genes and proteins expression levels.Result: In the present study, the muscle fiber diameter and the area of Normal soil and Antibacterial soil group were significantly higher than No soil group (P < 0.05). The Normal soil significantly upregulated the gene expression of MyoG compared to No soil and Antibacterial soil groups (P < 0.05). The gene expression of CD36 and CPT-1 of Normal soil group was significantly lower than No soil group (P < 0.05), while HSL expression of Normal soil group was significantly higher than Antibacterial and No soil groups (P < 0.05). The MyHC I of Normal soil group was significantly higher than No soil group (P < 0.05), but the expression MyHC IIa was lower than No soil group (P < 0.05). The protein expression expressed the similar result with gene expression. In addition, the Normal soil significantly increased the AMPK and mTOR phosphorylation compared to No soil and Antibacterial soil groups (P < 0.05).Conclusion: These data suggest that early exposure to topsoil regulates the muscle fiber growth, modulates the expression pattern related to myogenesis, muscle fiber type, intramuscular fat metabolism, and increases the phosphorylation of mTOR and AMPK pathways.