Using spline regression to determine the optimal levels of lysine for growing Japanese quail

This study was conducted to determine the optimal level of lysine in grower diet of Japanese quail by using 360 day old quail chicks in a 2×6 factorial arrangement [two levels of metabolisable energy 2850, and 2950 Kcal/kg) and six levels of lysine (1.1, 1.2, 1.3, 1.4, 1.5, and 1.6%)] in completely randomized design with three replicates and 10 birds per each. Feed intake and body weight were measured weekly and feed conversion ratiowas calculated. The optimum level of dietary lysine was assessed using spline regression. The results showed that daily weight gain and feed conversion ratio were improved by increasing the dietary lysine (P<0.05). The optimum level of lysine for the best daily weight gain during 1-21 and 22-35 days of age were estimated 1.39 and 1.40 for the birds fed on diet containing 2850 Kcal/kg metabolisable energy and 1.34 and 1.35 for the birds fed on diet containing 2950 Kcal/kg metabolisable energy, respectively. According to the results of this study, the best growth rate and feed efficiency in Japanese quail could be obtained by feeding diets containing 2850 Kcal/kg energy, 26% protein and 1.39% and 1.40% lysine for 1-22 and 22-35 days of age, respectively.