Effects of low‐protein diet supplementation with alpha‐ketoglutarate on growth performance, nitrogen metabolism and mTOR signalling pathway of skeletal muscle in piglets

Abstract

Excessive protein levels in diets result in incomplete digestion of nitrogenous nutrients that are excreted from the body, causing environment pollution. Alpha‐ketoglutarate (AKG) has been reported to decrease dietary protein levels, promote intestinal health in piglets and reduce environmental pollution. However, the underlying mechanisms of AKG are largely unknown. The objective of this study was to determine the effects of low‐protein diet supplementation of AKG on the growth performance, nitrogen metabolism, relative expression of amino acid transporter genes and mTOR signalling pathway of skeletal muscle in piglets. Forty‐eight piglets with an initial weight of 11.53 ± 0.04 kg were randomly divided into four groups. Each group had four replicates, and each replicate had three pigs. A low‐protein (LP) diet (crude protein was 14.96%) served as the control without AKG, while 0.5%, 1.0% and 1.5% AKG were added to the LP diet for the other experimental groups. The trial period lasted for 28 days. Compared with the LP group, the LP + 1.0%A and LP + 1.5%A groups increased the growth performance (p < .05);increased the mRNA levels of amino acid transporters in the duodenum, anterior jejunum and posterior jejunum (p < .05); and reduced faecal nitrogen and urine nitrogen emissions (p < .05). They also showed greater mRNA levels and phosphorylated protein levels for S6 kinase beta (S6K) (p < .05), mammalian target of rapamycin (mTOR) (p < .05) and 4E‐binding protein 1 (4EBP1) (p < .05) in skeletal muscle. An LP diet supplemented with AKG activated the mTOR signalling and promoted the ability of the small intestine to absorb protein, thereby increasing protein deposition. Taken together, an LP diet supplemented with AKG provides a theoretical basis for the promotion and application of AKG in piglet production.

Effects of Dietary Crude Protein Levels on Fecal Crude Protein, Amino Acids Flow Amount, Fecal and Ileal Microbial Amino Acids Composition and Amino Acid Digestibility in Growing Pigs

“…The research showed that adding crystalline AA to diets could improve the digestible energy, metabolizable energy and net energy of growing pigs [21]. Similarly, adding crystalline AA to low-protein diets can improve performance and carcass traits of late-breeding sows [16]. Other studies have shown that adding branched chain AA to low-protein diets can improve the growth performance in pigs to a level similar to that of adequate protein diets [22].…”

“…All results were expressed as mean ± standard error of mean (SEM). All data were subjected to a one-way analysis of variance using the general linear model (GLM) procedure of SAS 8.2 statistical software (SAS Institute, Inc. Cary, NC, USA) [16] according to a completely randomized one-factorial design. Differences among experimental groups were identified via the Student-Newman-Keuls (SNK) test.…”

“…Livestock and poultry excreta are important sources of environmental N pollution. In feeding and management, it has become an effective way to reduce nitrogen emissions by reducing the amount of protein raw materials to reduce dietary protein levels, and then by adding synthetic AA, to meet animal AA needs of low-protein diets [16]. Compared to feeding them the 18% CP diet, fecal N losses decreased by 7.4% and 18.3% when feeding the 15% and 12% (protein-free) CP diet, respectively.…”

Effect of Reduced Crude Protein Level on Fecal Nitrogen Excretion and Blood Profile in Finishing Pigs

“…Pig products are a significant source of environmental nitrogen pollution [14]. In feeding management, controlled reduction of protein feed to reduce total protein levels in the ration and addition of synthetic forms of amino acids to meet their needs has become an effective way to reduce nitrogen emissions [15]. This manipulation to reduce ammonia emissions appears to be a highly effective and efficient method in pig farming [16; 17].…”

Low Protein Diets Supplemented With Alpha-Ketoglutarate Enhance the Growth Performance, Immune Response, and Intestinal Health in Common Carp (Cyprinus carpio)

“…AKG has a great effect on promoting the absorption and metabolism of amino acids. The addition of AKG could enhance energy status and muscle mass by activating mechanistic target of rapamycin (mTOR) signaling pathway in piglets ( 10 ). Previous studies have also demonstrated that dietary AKG supplementation improved the growth performance and protein deposition of juvenile hybrid sturgeon ( Acipenser schrenckiif × A.baeriio ) ( 11 ).…”