1. The present experiment was designed to examine arginine (Arg)-sparing effects of guanidinoacetic acid (GAA) on production performance, intestinal morphology and certain blood parameters in broiler chickens. 2. A total of 300 male broiler chicks (Ross 308) were randomly allotted to 5 dietary treatments in a completely randomised design during 1-15 and 15-35 d rearing periods. Experimental treatments consisted of a basal diet with a reduction in Arg content (CON-; starter: 12.1 g/kg and grower: 11.3 g/kg Arg), a CON- diet supplemented with synthetic Arg equal to the required Arg level (CON+; starter: 13.80 g/kg; grower: 12.37 g/kg) and CON- diet supplemented with three levels of GAA (GAA0.6; GAA1.2; and GAA1.8; g/kg). 3. Supplemental GAA at 0.6 and 1.2 g/kg reduced the adverse effects of the CON- diet on weight gain and feed conversion ratio in the starter period, equal to the effect of CON+ diet. During the entire rearing period, such an effect was only seen for broilers fed CON- diet supplemented with 1.2 and 1.8 g/kg GAA (P < 0.05). Proportional weights of liver and abdominal fat were decreased in birds fed diets containing supplemental Arg and 1.8 g/kg GAA compared to the CON- broilers (P < 0.05). Jejunal villus height and villus height to crypt depth ratio were increased in broilers receiving the CON- diet (P < 0.05). Serum concentration of nitric oxide increased when the CON- diet was supplemented with either Arg or 1.8 g/kg GAA (P < 0.05). 4. Dietary inclusion of GAA had an Arg-sparing effect, whereby 1.2 and 1.8 g/kg of supplemental GAA resulted in greater growth performance during the starter and entire rearing periods, respectively. Supplementation with 1.8 g/kg GAA had significant effects on some carcass and physiological parameters.
Keywords: Arginine deficiency; blood parameters; broiler chickens; guanidinoacetic acid; intestinal morphology.