Effects of dietary leucine and tryptophan on serotonin metabolism and growth performance of growing pigs

Abstract

An experiment was conducted to test the hypothesis that increased dietary Trp is needed in high-Leu diets for growing pigs to prevent a drop in plasma serotonin and hypothalamic serotonin concentrations and to maintain growth performance of animals. A total of 144 growing pigs (initial weight: 28.2 ± 1.9 kg) were assigned to 9 treatments in a randomized complete block design with 2 blocks, 2 pigs per pen, and 8 replicate pens per treatment. The 9 diets were formulated in a 3 × 3 factorial with 3 levels of dietary Leu (101, 200, or 299% standardized ileal digestible [SID] Leu:Lys), and 3 levels of dietary Trp (18, 23, or 28% SID Trp:Lys). A basal diet that met requirements for SID Leu and SID Trp was formulated and 8 additional diets were formulated by adding crystalline L-Leu and (or) L-Trp to the basal diet. Individual pig weights were recorded at the beginning of the experiment and at the conclusion of the 21-d experiment. On the last day of the experiment, one pig per pen was sacrificed, and blood and hypothalamus samples were collected to measure plasma urea N, plasma serotonin, and hypothalamic serotonin concentrations. Results indicated that increasing dietary Trp increased (P < 0.05) hypothalamic serotonin, whereas increases (P < 0.05) in average daily gain (ADG) and average daily feed intake (ADFI) were observed only in pigs fed diets containing excess Leu. Increasing dietary Leu reduced (P < 0.05) ADG, ADFI, and hypothalamic serotonin. However, the increase in ADG and ADFI caused by dietary Trp was greater if 299% SID Leu:Lys was provided than if 101% SID Leu:Lys was provided (interaction, P < 0.05). Plasma Leu concentration was positively affected by dietary Leu and negatively affected by dietary Trp, but the negative effect of Trp was greater if 299% SID Leu:Lys was provided than if 101% SID Leu:Lys was provided (interaction, P < 0.05). Plasma concentration of Trp was positively affected by increased dietary Trp and increased dietary Leu, but the increase in plasma concentration of Trp was greater if Leu level was at 101 % SID Leu:Lys ratio than at 299% SID Leu:Lys ratio (interaction, P < 0.05). In conclusion, increased dietary Leu reduced ADG, ADFI, and hypothalamic serotonin concentration, and influenced metabolism of several indispensable amino acids, but Trp supplementation partly overcame the negative effect of excess Leu. This demonstrates the importance of Trp in regulation of hypothalamic serotonin, and therefore, feed intake of pigs.

A corn-fermented protein ingredient can be included in early nursey diets without compromising pig growth performance and health status

“…Similar to this work, at high Leu:Lys ratios, growth performance of weaned pigs was reduced. The effect of high Leu:Lys ratio when main protein sources are replaced with GDDY or other corn-fermented protein products ( Yang et al 2018a , Cemin et al 2021 ) has been well documented in growing-finishing pigs ( Rojo 2011 , Cemin et al 2019 , Clizer 2021 , Kwon et al 2022 ). It is suggested that in growing finishing pigs Leu:Lys ratios above 150% are expected to negatively impact performance ( Htoo et al 2014 , Cemin et al 2019 , Kwon et al 2019 ).…”

Leucine regulates lipid metabolism in adipose tissue through adipokine-mTOR-SIRT1 signaling pathway and bile acid–microbe axis in a finishing pig model

“…In the present study, Leu supplementation did not significantly affect ADFI of growing pigs, probably because the coordination between small amounts of Leu, valine, isoleucine and tryptophan in the diet had no significant effect on the serotonin production by the hypothalamus. Most studies have focused on the effects of excessive Leu supplementation on hypothalamic serotonin release in piglets or growing pigs, but there are few studies on whether low levels of Leu supplementation promote serotonin release ( Kwon et al., 2019b , 2022 ; Wessels et al., 2016 ). Average backfat thickness, loin-eye area, lean meat percentage and total fat percentage are important indicators of carcass weight.…”

Systems biology and metabolic modeling for cultivated meat: A promising approach for cell culture media optimization and cost reduction

“…To our knowledge, there are no currently available GEMs for pigs; however, nutrition studies from whole animal production can provide insights into essential nutrients for cell culture. Animal science studies on pig metabolism have shown that lysine and tryptophan are limiting amino acids in swine diets and impact growth performance (Hasan et al., 2020; Kwon et al., 2022). Additionally, pig residual feed intake, a sensitive and accurate indicator of feed efficiency, is correlated to the expression of genes ( phosphatidylcholine:ceramide cholinephosphotransferase 1 [ SGMS1 ], phosphatase and tensin homolog [ PTEN ], arachidonate 12‐lipoxygenase, 12S type [ ALOX12 ], protein kinase Adenosine Monophosphate (AMP)‐ activated non‐catalytic subunit gamma 3 [ PRKAG3 ], 1‐phosphatidylinositol‐ 4,5‐bisphosphate phosphodiesterase delta‐4 [ PLCD4 ]) highly involved in porcine lipid metabolic processes (Do et al., 2014).…”