Effects of dietary lysine levels on plasma free amino acid profile in late-stage finishing pigs

Abstract

Muscle growth requires a constant supply of amino acids (AAs) from the blood. Therefore, plasma AA profile is a critical factor for maximizing the growth performance of animals, including pigs. This research was conducted to study how dietary lysine intake affects plasma AA profile in pigs at the late production stage. Eighteen crossbred (Large White × Landrace) finishing pigs (nine barrows and nine gilts; initial BW 92.3 ± 6.9 kg) were individually penned in an environment controlled barn. Pigs were assigned randomly to one of the three dietary treatments according to a randomized complete block design with sex as block and pig as experiment unit (6 pigs/treatment). Three corn- and soybean meal-based diets contained 0.43 % (lysine-deficient, Diet I), 0.71 % (lysine-adequate, Diet II), and 0.98 % (lysine-excess, Diet III) l-lysine, respectively. After a 4-week period of feeding, jugular vein blood samples were collected from the pigs and plasma was obtained for AA analysis using established HPLC methods. The change of plasma lysine concentration followed the same pattern as that of dietary lysine supply. The plasma concentrations of threonine, histidine, phenylalanine, isoleucine, valine, arginine, and citrulline of pigs fed Diet II or III were lower (P < 0.05) than that of pigs fed Diet I. The plasma concentrations of alanine, glutamate, and glycine of pigs fed Diet II or III were higher (P < 0.05) than that of pigs fed Diet I. The change of plasma leucine and asparagine concentrations followed the patterns similar to that of plasma lysine. Among those affected AAs, arginine was decreased (P < 0.05) in the greatest proportion with the lysine-excess diet. We suggest that the skeletal muscle growth of finishing pigs may be further increased with a lysine-excess diet if the plasma concentration of arginine can be increased through dietary supplementation or other practical nutritional management strategies.

Effects of dietary lysine levels on the concentrations of selected nutrient metabolites in blood plasma of late‐stage finishing pigs

“…The effects of dietary lysine on the blood plasma free AA profile along with some growth performance data generated from this project were reported previously by Regmi et al (2016). This report focuses on the plasma concentrations of the selected nutrient metabolites as follows.…”

“…For the late‐stage finishing pigs as used in this study, one of the initial hypotheses was that the adequacy of dietary lysine might increase protein synthesis and thus increase the plasma concentration of total protein. However, the unchanged plasma concentration of total protein but increased BW gain (Regmi et al., ) resulting from the lysine‐adequate diet indicates a homoeostatic control of plasma total protein concentration and a preferential utilization of AA for syntheses of albumin and muscle proteins (Wang et al., ).…”

A Systems Biology Approach Using Transcriptomic Data Reveals Genes and Pathways in Porcine Skeletal Muscle Affected by Dietary Lysine

“…This study revealed that dietary lysine deficiency increased the expression of PHGDH and PSPH mRNA, responsible for coding 2 rate-limiting enzymes in the serine and glycine biosynthesis pathway (Figure 6), and these increases indicated a positive serine and/or glycine biosynthesis in the skeletal muscle of the finishing pigs. One of our previous studies showed that the plasma concentrations of serine (numerically) and glycine (P ≤ 0.05) were both decreased in the pigs fed a lysine-deficient diet [33], and these decreases suggested that there might not be enough serine and glycine supply in the plasma, causing active serine and glycine biosyntheses in skeletal muscle. Since serine and glycine are building blocks for protein synthesis and substrates for creatine, purine, and pyrimidine generation [34], the change of PHGDH and PSPH mRNA levels implies that dietary lysine could affect muscle energy metabolism, and the biosyntheses of nuclear acids and proteins.…”

“…The AMD1 mRNA level affected by dietary lysine may lead to a change in the polyamine level causing differential muscle growth. Regmi et al [33] reported that the plasma concentration of arginine decreased along with the increased dietary lysine concentration. Since arginine is the main substrate for polyamine synthesis [37], the regulation of dietary lysine on AMD1 expression and then polyamine level may be due to the antagonism effect of lysine on plasma arginine level.…”

Homeostatic regulation of plasma amino acid concentrations

“…Because the endogenous source of AAs originally also came from the diet and pigs cannot readily utilize the microbial proteins resulting from the intestinal fermentation, it can be stated that pigs solely depend on their diets for the supply of non-synthesizable AAs. While the influence of dietary AAs on the plasma AA profile is not easy to be understood (56), numerous studies were conducted in the past to determine the relationship between plasma AA concentrations and dietary AA supply (54,(59)(60)(61). Although the published results did not always support each other, different researchers have tried different sources and compositions of dietary AAs with hopes to find out the alteration patterns of AA concentrations in the blood plasma.…”