Dietary glycine equivalent and SID methionine+ cysteine levels for male broiler chickens fed low crude protein diets

Abstract

This study was conducted to determine the optimum dietary glycine equivalent (Glyequi) level in low crude protein (LCP) diets of 181 g/kg containing varied concentrations of standardized ileal digestible (SID) methionine+cysteine (Met+Cys) for broiler chicks (1-21d old). A total of 1275, 1-d-old Cobb-Vantress® male broilers were distributed in a 5 × 3 factorial arrangement of completely randomized design of 15 treatments with five replicates of 17 birds each. Treatments consisted of 5 levels of dietary Glyequi (14.9, 16.4, 17.9, 19.4 and 20.6 g/kg) and three concentrations of SID Met+Cys (7.70, 9.0 and 10.3 g/kg). Interactions between Glyequi and SID Met+Cys levels were observed for feed:gain (P = 0.055) and breast meat yield (BMY) (P = 0.017). In 7.7 and 9.0 g SID Met+Cys/kg diets, optimal feed:gain and increased BMY were observed at the Glyequi level not lower than 17.9 g/kg. In 10.3 g SID Met+Cys/kg diet, a lower feed:gain was achieved at 19.4 g Glyequi/kg. Therefore, a minimum dietary level of 17.9 g Glyequi/kg is needed to increase growth of broilers fed diets containing 7.7 or 9.0 g/kg SID Met+Cys while 19.4 g/kg Glyequi is necessary in diets containing 10.3 g/kg SID Met+Cys for optimum growth.