Dietary supplementation with lysine and threonine modulates the performance and plasma metabolites of broiler chicken

Abstract

Here, we investigatedwhether the optimal threonine (Thr) to lysine (Lys) ratio in high Lys diet improves the growth performance of modern broiler chickens at finisher periodandd eterminedthe possible mechanism underlying improvement in the growth performance of chickens fedwith high Lys or Lys + Thr diet using metabolome analyses. Eighteen 21-day-old chickens housed in individual cages were randomly divided into three groups of six chickens fed with different diets as follows: Control diet, high Lys diet (150% Lys content of National Research Council requirement), andhigh Lys + Thr diet (0.68 of Thr/Lys in high Lys diet). Body weight gain (BWG) increased in chickens receiving high Lys diet as comparedwith those fedwith the control diet (P＜0.05); no significant difference was observedin BWG of chickens from high Lys + Thr andhigh Lys groups. Feedconversion ratio (FCR) was lower in chickens fedwith high Lys or high Lys + Thr diet than in those on the control diet. Serotonin concentration increasedin the plasma of chickens fedwith high Lys diet as comparedto those fedwith other diets. A negative correlation was observedbetween plasma serotonin concentration andFCR. These results provide the first evidence on the use of high Lys in broiler diets to reduce FCR during finisher period, which may be associated with change in plasma serotonin concentration. These findings suggest that high Lys content in finisher diet, but not high Thr + Lys diet, may affect the peripheral serotonergic metabolism and improve FCR. Thus, plasma serotonin may serve as a biomarker of FCR in broilers.