PERFORMANCE AND MUSCULAR CREATINE OF BROILER CHICKENS FED LOW PROTEIN DIETS CONTAINING VARYING GLYCINE EQUIVALENT AND THREONINE LEVELS

Abstract

This study was conceived and aimed to investigate the interactive effects of a glycine equivalent (Glyequi) and standardized ileal digestible threonine (SID Thr) levels in low crude protein diets on performance and muscular creatine content in broiler chickens from 21 to 42 days. A total of 1500, 21-day-old Cobb-Vantress® male broiler chickens were distributed in a completely randomized 5 × 3 factorial arrangement of Glyequi × SID Thr with five replicates of 20 birds each. Fifteen dietary treatments of 16.5% CP were formulated to contain five levels of total Glyequi (1.16, 1.26, 1.36, 1.46 and 1.56%) and three levels of SID Thr (0.58; 0.68 and 0.78%). Interactive effects (p<0.05) of Glyequi and SID Thr levels were observed for weight gain, carcass yield, and muscular creatine content. Higher levels of Glyequi increased (p = 0.040) weight gain in 0.58 and 0.68% SID Thr diets compare to the 0.78% SID Thr diet. Levels of Glyequi equal to or above 1.26% in diets with 0.78% SID Thr resulted in birds with higher (p=0.033) muscular creatine content. There was a quadratic effect of Glyequi levels for muscular creatine content (p = 0.008) with an estimated optimal levels of 1.47% Glyequi. Therefore, the minimum dietary level of Glyequi needed to improve performance in low crude protein diets is 1.26% with adequate SID Thr levels for broiler chickens.