Excess leucine in diets for growing pigs negatively affects growth performance, nitrogen balance, and metabolism of branched-chain amino acids and tryptophan

Five experiments were conducted to determine the effects of excess dietary Leu on metabolism of branched-chain amino acids (BCAA) and to demonstrate the interactions among BCAA and Trp in diets fed to growing pigs. In experiment 1, the objective was to determine the effects of excess dietary Leu on growth performance, N balance, protein retention, and serotonin synthesis of growing pigs. Results indicated that average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio decreased (linear, P < 0.05) as dietary Leu increased. Decreased (linear, P < 0.05) biological value of dietary protein was also observed, and plasma urea N (PUN) increased (linear, P < 0.05) as dietary Leu increased. A linear reduction (P < 0.05) in hypothalamic serotonin was observed with increasing dietary Leu. In experiment 2, the objective was to determine effects of dietary Ile and Val supplementation to diets with adequate or excess Leu on N balance and BCAA metabolism of growing pigs. Results indicated that excess Leu in diets reduced (P < 0.05) N retention and biological value of diets and increased (P < 0.05) PUN, but PUN was reduced (P < 0.05) as dietary Val increased. Concentrations of BCAA in liver were greater (P < 0.05) in pigs fed excess-Leu diets than in pigs fed adequate-Leu diets, but concentrations of BCAA in muscle were greater (P < 0.05) in pigs fed adequate-Leu diets. Increasing dietary Ile increased (P < 0.05) plasma free Ile and plasma concentration of the Ile metabolite, α-keto-β-methylvalerate, but the increase was greater in diets with adequate Leu than in diets with excess Leu (interaction, P < 0.001). Likewise, plasma concentrations of Val and the Val metabolite, α-keto isovalerate, increased more with increasing dietary Val in diets with Leu at the requirement than in diets with excess Leu (interaction, P < 0.001). Increasing dietary Leu increased (P < 0.05) plasma free Leu and plasma concentration of the Leu metabolite, α-keto isocaproate. In contrast, increased dietary Val reduced (P < 0.05) plasma concentration of α-keto isocaproate. Experiment 3 was conducted to determine interactions between dietary Trp and dietary Leu on plasma serotonin and hypothalamic serotonin concentrations and growth performance of growing pigs. Results indicated that increasing dietary Trp increased (P < 0.05) ADG, ADFI, and hypothalamic serotonin whereas increasing dietary Leu reduced (P < 0.05) ADG, ADFI, and hypothalamic serotonin, but the increase caused by dietary Trp was greater if Leu was provided at 300% of the requirement than if it was provided at the requirement (interaction, P < 0.05). Experiments 4 and 5 were conducted to test the hypothesis that increasing concentrations of dietary Val, Ile, or Trp in diets containing excess Leu from corn protein mitigate negative effects of excess dietary Leu on N balance, PUN, and growth performance of growing pigs. Results from experiment 4 indicated that fecal N output increased if Ile was added to diets without added Val, but that was not the case if Val was added (interaction, P < 0.05). Addition of Ile to diets reduced N retention, and N retention increased with Trp addition to diets without Val addition, but not in diets with added Val (interaction, P < 0.05). The biological value of protein increased if Trp was added to diets without addition of Ile, but if Ile was added, Trp addition did not increase the biological value of protein (interaction, P < 0.05). Results from experiment 5 indicated that final body weight and ADG of pigs fed a diet with exces Leu were reduced compared with pigs fed a corn-soybean meal control diet. However, if Val and Trp were added to the diet with excess Leu ADG and final body weight were not different from that obtained for pigs fed the corn-soybean meal control diet. In conclusion, results of these experiments indicate that excess dietary Leu may have negative impacts on N balance, metabolism of BCAA, and growth performance of pigs. Excess dietary Leu also may reduce serotonin synthesis in the hypothalamus, which may have contributed to the reduced ADFI observed for pigs fed diets with excess Leu. However, increasing concentrations of dietary Trp and Val alone or in combination may have the potential to alleviate the negative effects of excess dietary Leu.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Kwon, Woongbi

Contributors dc:contributor

• Stein, Hans H
• Parsons, Carl M
• Pan, Yuan-Xiang
• Emmert, Jason L

• branched-chain amino acids
• growth performance
• nitrogen balance
• serotonin
• tryptophan

Statement dc:rights

• © 2020 Woongbi Kwon

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/108516

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/108516