This experiment was conducted to investigate the effects of guanidinoacetic acid (GAA) on productive performance, intestinal morphometric features, blood parameters and energy utilisation in broiler chickens. A total of 390 male broiler chicks (Ross 308) were assigned to six dietary treatments based on a factorial arrangement (2×3) across 1-15 and 15-35-d periods. Experimental treatments consisted of two basal diets with standard (STD; starter: 12·56 MJ/kg and grower: 12·97 MJ/kg) and reduction (LME; starter: 11·93 MJ/kg and grower: 12·33 MJ/kg) of apparent metabolisable energy (AME) requirement of broiler chickens each supplemented with 0, 0·6 and 1·2 g/kg GAA. Supplemental 1·2 g/kg GAA decreased the negative effects of feed energy reduction on weight gain across starter, growing and the entire production phases (P<0·05). Energy retention as fat and total energy retention were increased when birds received LME diets supplemented with 1·2 g/kg GAA (P<0·05). Net energy for production (NEp) and total heat production increased in birds fed LME diets containing 1·2 g/kg GAA (P<0·05). A significant correlation was observed between dietary NEp and weight gain of broilers (r 0·493; P=0·0055), whereas this relationship was not seen with AME. Jejunal villus height and crypt depth were lower in birds fed LME diets (P<0·05). Serum concentration of creatinine increased in broilers fed LME diets either supplemented with 1·2 g/kg GAA or without GAA supplementation (P<0·05). Supplemental GAA improved performance of chickens fed LME diet possibly through enhanced dietary NEp. The NEp could be preferred over the AME to assess response of broiler chickens to dietary GAA supplementation.
Keywords: AIA acid-insoluble ash; AME apparent metabolisable energy; CFr total carcass fat retention; DWG daily weight gain; FCR feed conversion ratio; GAA guanidinoacetic acid; GE gross energy; HP heat production per kg of feed intake; HP total heat production; LME basal diet with energy reduction below the level recommended by Ross 308 (2014) broiler manual (starter: 11·93 MJ/kg and grower: 12·33 MJ/kg); NE net energy for production; RE carcass gross energy retained as carcass fat; RE carcass gross energy retained as carcass protein; RE energy retained in the carcass; STD basal diet with energy level recommended by Ross 308 (2014) broiler manual (starter: 12·56 MJ/kg and grower: 12·97 MJ/kg); TP total protein; UA uric acid; Broiler chickens; Energy retention; Guanidinoacetic acid; Intestinal morphology; Net energy.