بررسی اثر سطوح مختلف پروتئین خام، متیونین و بتائین بر عملکرد و شاخص‌های لاشه جوجه‌های گوشتی

This experiment was conducted to evaluate the effects of dietary levels of crude protein, methionine and betaine on performance and carcass characteristics of broiler chickens. A total of 640 one-day-old broiler chicks from Ross 308 strain were used. Each pen (1.5 ×1.5m) was assumed as experimental unit and was included 20 male and female chicks. The experiment was conducted based on completely randomized design as a 2×2×2 factorial arrangement. The chicks were reared on the basis of regular brooding procedures until 7 days of age and then were fed with diets containing 2 levels of crude protein (high and medium), 2 levels of methionine (high and medium) and 2 levels of betaine (0 and 0.08%) from 7 to 42 days of age. All experimental diets were prepared isocaloric. Average daily feed intake, average daily weight gain and feed conversion ratio was measured weekly. At day 42 of age, one male bird from each pen was selected and slaughtered for carcass analysis. Results of this experiment showed that none of treatments had a significant effect on feed intake in 7 to 42 days of age (P> 0.05). Betaine fed groups showed more daily feed consumption in compare to other groups but this effect was only significant during 14-21 days of age (P< 0.05). Higher level of crude protein and 0.08% betaine significantly improved body weight of the birds (P< 0.05). Birds fed diets containing betaine and high level of crude protein had higher daily weight gain than other groups. The main effects of crude protein, methionine and betaine had no significant effect on performance characteristics of broiler chickens. The abdominal fat pad of broilers fed with treatment 3 (high protein, high methionine, no betaine) was lower than other treatments. In general, according to the result of this study some part of methionine can be replaced by betaine in broilers diet.