No abstract

High levels of guanidinoacetate acid (GAA) deteriorate growth response in broiler chickens. We propose using coenzyme Q10, an antioxidant, and taurine (TAU), a methyl donor, to cope with the situation when high level of GAA included in diet. GAA was supplemented at 0 (control), 0.75, 1.5 and 2.25 g/kg in isoenergetic and isonitrogenous diets and fed to broilers (Cobb 500) from 1 to 40 days post‐hatch. Three additional diets were prepared by adding CoQ10 (40 mg/kg), TAU (40 mg/kg) or their combination (both CoQ10 and TAU at 40 mg/kg) to the 2.25 g/kg GAA group. The experimental design used was a completely randomized design. While weight gain (p = 0.038) and feed conversion ratio (p = 0.024) improved when GAA added at 1.5 g/kg, higher supplementation (2.25 g/kg) deteriorated these responses. These responses, however, were significantly restored by using CoQ10, TAU or their combination. Abdominal fat deposition was significantly decreased when TAU added to broiler diets by virtue of upregulating peroxisome proliferator‐activated receptor alpha. Supplementing broiler diets with CoQ10 and TAU or their combination significantly decrease ascites mortality. In conclusion, CoQ10 and TAU have shown beneficial effects when high level of GAA included in broiler diets.

In order to estimate arginine (Arg) requirements of male broilers (Ross 308) during the 21-to 42-day period and exposed to hypobaric condition, six diets (200 g/kg CP and 13.4 MJ ME/kg) with graded levels of Arg (8.8 to 14.3 g/kg) were allocated to four pens of twelve birds each. Body weight gain, feed:gain, breast meat yield, plasma nitric oxide (NO) concentration, and right to total ventricular weight ratio (RV/TV) were determined as response criteria. Responses to Arg supply were nonlinear and attained plateau values (y max ) within the studied range of Arg supply. The estimated Arg requirements for maximal body weight gain and optimal feed:gain during the 21 days under study were 12.4, and 12.2 g/kg of diet, respectively. The estimated Arg requirement for maximizing breast meat yield was 12.6 g/kg of diet. Based on the response in plasma NO and RV/TV, the estimated requirements were 13.0, and 13.2 g/kg of diet, respectively. Data obtained for the individual factors clearly indicate that the NRC recommendations for Arg are not sufficient for maximizing body weight gain, optimizing feed:gain and preventing the onset of pulmonary hypertension in broiler chickens exposed to hypobaric condition. Data may be used for future modeling of broilers' Arg requirements.

Abstract:The effect of using a low protein regime in pullet development and subsequent layer performance was studied. The experiment consisted of two periods of rearing and laying. Two hundred and sixty Hy-line W36 chicks were used. In the rearing period, dietary protein level and ME content series of the control group used during starter (18-42), grower (43-63) and developer (64-119d) phases were 20, 2930, 18, 2930, and 16, 3025, respectively. Dietary protein sequence of the low protein group was 18.5, 16.5, and 14.6% during the respective periods. In the laying period lasted from week18 to week32 of age, CP content of the control and reduced-protein diets were 17.8 and 16.3%, respectively. Reduced-protein diets were kept isoenergetic with their corresponding controls in each period and phase and they balanced to keep the same total sulfur amino acid to lysine ratio as well. Results indicated that birds on reduced-protein diet during starter phase of the rearing period consumed less feed (p = 0.003) and as a result they had significantly (p = 0.012) better feed conversion ratio (FCR) compared to the control. However, dietary protein regime had no significant effect on weight gain, feed intake and FCR during grower and developer phases. In the laying period, there was no significant difference in terms of layer performance and egg quality criteria. In conclusion, reduced-CP diets can be satisfactory used for rearing pullets and laying hens up to 32 weeks of age.