The Optimum Ratio of Digestible Leucine: Lysine in Wheat-based Diets for Female Broiler Chickens From 8-21 Days of Age

Leucine (Leu) is one of the essential amino acids, and has a direct effect on protein biosynthesis in broiler skeletal muscle. So supply of sufficient amounts of Leu in young broiler is of interest. Therefore, the purpose of the current study was to estimate the optimal digestible Leu in ratio to lysine (Lys) of female broiler chickens from 8 to 21 d. A dose-response trial was performed, and the optimal digestible Leu was estimated applying broken-lines and quadratic regression models. A total of 540 one-wk-old female broiler chickens (Cobb-500), were randomly distributed to 6 dietary treatments (6 replicate of 15 birds in each), and fed the experimental diets from 8 to 21 d of age. Dietary digestible Leu was supplied from 0.93% up to 1.18% in 0.05% increments. Wheat-soybean meal based diet was formulated to be deficient in Leu, and dietary treatments were created by gradually replacing crystalline L-glutamic acid with crystalline L-Leu in basal diet. The live performance and carcass traits were evaluated, and excretion and retention of nitrogen was measured. The results showed that weight gain (WG), feed intake (FI), carcass weight, and breast weight had a quadratically response to digestible Leu: Lys from 0.93 to 1.18. Also, none of the retention and excretion of nitrogen were affected by increasing dietary digestible Leu levels. Based on the obtained data in the current study, the optimal digestible Leu: Lys of female Cobb 500 broilers fed with wheatbased diets from 8 to 21 d of age was estimated between 0.99 and 1.12 with an average of 1.06 based on quadratic broken-line model as the concluded value.

Automated summary

The purpose of this study was to estimate the optimal digestible Leucine (Leu) to Lysine (Lys) ratio for female broiler chickens from 8 to 21 days old. The results showed that a digestible Leu: Lys ratio ranging from 0.93% to 1.18% had the best impact on the growth and carcass traits of the broiler chickens.