Effects of Dietary Lysine Levels on the Plasma Concentrations of Growth‐Related Hormones in Late‐Stage Finishing Pigs

Abstract

This study was undertaken to investigate the effects of dietary lysine on the plasma concentrations of three growth-related hormones in pigs. Nine late-stage finishing barrows were assigned to three dietary treatments according to a completely randomized experimental design (3 pigs/treatment). Three corn and soybean meal-based diets were formulated to contain three levels of lysine, which were 0.43, 0.71, and 0.98% for Diets 1 (lysine deficient), 2 (lysine adequate), and 3 (lysine excess), respectively. The feeding trial lasted 4 weeks, during which the pigs were allowed ad libitum access to the diets and water. After the 4 weeks, blood was collected and plasma samples were obtained. Then, the plasma concentrations of insulin, growth hormone (GH), and insulin-like growth factor 1 (IGF-1) were measured. No difference in the plasma concentration of insulin or GH among the three treatments was found (P > 0.10). However, the plasma IGF-1 concentration was lower (P < 0.05) in the pigs fed Diet 1 or 3 than fed Diet 2, suggesting that either dietary lysine deficiency or excess can lead to a lower concentration of plasma IGF-1. It was concluded that IGF-1, instead of insulin or GH, in the blood may be a key controlling growth factor in response to dietary lysine supply for regulating muscle growth in late-stage finishing pigs.

Dietary lysine affects amino acid metabolism and growth performance, which may not involve the GH/IGF-1 axis, in young growing pigs1

“…Previous research showed that the level of dietary lysine can have significant effect on the growth performance of pigs (O'Connell et al, 2006;Kim et al, 2011;Taylor et al, 2015). Our previous studies (Regmi et al, 2016(Regmi et al, , 2018Wang et al, 2017) also showed that dietary lysine deficiency (i.e., restriction) significantly compromised the growth performance of the latestage finishing pigs, and this compromise was associated with the observed changes in the plasma concentrations of some nutrient metabolites (including some AA) and a growth-related hormone, insulin-like growth factor 1 (IGF-1). However, similar studies on young growing pigs are still limited.…”

“…Similar result was reported by Roy et al (2000), who reported that dietary lysine levels did not affect the plasma concentrations of GH and IGF-1 in growing pigs. Wang et al (2017) found that there was no effect of dietary lysine levels on the plasma concentrations of GH and insulin in late-stage finishing pigs.…”

“…Additionally, it is also known that different AA have different potencies of insulinotropic property, and lysine or arginine appeared to be the most potent one (Floyd et al, 1966;Fajans et al, 1969;Wang et al, 2017). Ren et al (2007) reported that the plasma insulin concentration was increased when growing Means within a row that have different superscripts differ (P < 0.05).…”

“…For the plasma concentrations of the selected hormones, three commercial ELISA kits were employed for the measurements, as previously reported by Wang et al (2017). The porcine growth hormone (GH, a.k.a.…”

“…Of these, the GH/IGF-1 axis is one of the primary regulatory systems for animal growth and this axis is sensitive to animal nutritional status (Brameld et al, 1998;Breier, 1999;Jiang and Ge, 2014). Katsumata et al (2002) reported that dietary lysine deficiency reduced the plasma IGF-1 concentration by 52% in growing pigs, whereas Wang et al (2017) reported that the plasma IGF-1 concentration was decreased when finishing pigs were fed either a lysine deficient or a lysine excess diet.…”