Dietary arginine supplementation increases growth of neonatal pigs, but the underlying mechanisms are unknown. This study was conducted to test the hypothesis that the arginine treatment activates translation initiation factors and protein synthesis in skeletal muscle. Piglets were fed milk-based diets supplemented with 0 or 0.6% L-arginine between 7 and 14 d of age. Following a 7-d period of arginine supplementation, at 1 h after the last meal, jugular venous blood samples were obtained for metabolite analysis, whereas longissimus muscle and liver were collected to determine the abundance and phosphorylation state of the mammalian target of the rapamycin (mTOR), ribosomal protein S6 kinase 1 (S6K1), eukaryotic initiation factor (eIF) 4E-binding protein-1 (4E-BP1), eIF4E, and eIF4G. Fractional rates of protein synthesis were measured in muscle and liver using the [(3)H]phenylalanine flooding-dose technique. Arginine supplementation increased (P < 0.05) daily gain, the plasma insulin concentration, and protein synthesis in skeletal muscle but not in liver. The arginine treatment enhanced the formation of the active eIF4E x eIF4G complex but reduced the amount of the inactive 4E-BP1 x eIF4E complex in muscle. These changes were associated with elevated levels of phosphorylated mTOR and 4E-BP1 in muscle of arginine-supplemented piglets (P < 0.05). Neither the total amounts nor phosphorylation levels of the translation initiation factors in the liver differed between control and arginine-supplemented piglets. Collectively, these results suggest that dietary arginine supplementation increases mTOR signaling activity in skeletal muscle, but not in liver, of milk-fed neonatal pigs. The findings provide a molecular mechanism for explaining the previous observation that increased circulating arginine stimulated muscle protein synthesis and promoted weight gain in neonatal pigs.

Mucosa-associated microbiota from different regions of the gastrointestinal (GI) tract of adult broilers was studied by analysis of 16S rRNA gene sequences. The microbiota mainly comprised Gram-positive bacteria along the GI tract. Fifty-one operational taxonomic units (OTUs) (from 98 clones) were detected in the ceca, as compared with 13 OTUs (from 49 clones) in the crops, 11 OTUs (from 51 clones) in the gizzard, 14 OTUs (from 52 clones) in the duodenum, 12 OTUs (from 50 clones) in the jejunum and nine OTUs (from 50 clones) in the ileum. Ceca were dominantly occupied by clostridia-related sequences (40%) with other abundant sequences being related to Faecalibacterium prausnitzii (14%), Escherichia coli (11%), lactobacilli (7%) and Ruminococcus (6%). Lactobacilli were predominant in the upper GI tract and had the highest diversity in the crop. Both Lactobacillus aviarius and Lactobacillus salivarius were the predominant species among lactobacilli. Candidatus division Arthromitus was also abundant in the jejunum and ileum.

Obesity in humans is a major public health crisis worldwide. In addition, livestock species exhibit excessive subcutaneous fat at market weight. However, there are currently few means of reducing adiposity in mammals. This study was conducted with a swine model to test the hypothesis that dietary L-arginine supplementation may increase muscle gain and decrease fat deposition. Twenty-four 110-day-old barrows were assigned randomly into two treatments, representing supplementation with 1.0% L-arginine or 2.05% L-alanine (isonitrogenous control) to a corn- and soybean meal-based diet. Growth performance was measured based on weight gain and food intake. After a 60-day period of supplementation, carcass and muscle composition were measured. Serum triglyceride concentration was 20% lower (P < 0.01) but glucagon level was 36% greater (P < 0.05) in arginine-supplemented than in control pigs. Compared with the control, arginine supplementation increased (P < 0.05) body weight gain by 6.5% and carcass skeletal-muscle content by 5.5%, while decreasing (P < 0.01) carcass fat content by 11%. The arginine treatment enhanced (P < 0.05) longissimus dorsi muscle protein, glycogen, and fat contents by 4.8, 42, and 70%, respectively, as well as muscle pH at 45 min post-mortem by 0.32, while reducing muscle lactate content by 37%. These results support our hypothesis that dietary arginine supplementation beneficially promotes muscle gain and reduces body fat accretion in growing-finishing pigs. The findings have a positive impact on development of novel therapeutics to treat human obesity and enhance swine lean-tissue growth.