اثر ميزان انرژي و زمان تعويض جيره هاي پيش دان به پس دان بر عملكرد توليدي جوجه هاي گوشتي با وزن كمتراز دوكيلوگرم

An experiment with a 3x3 factorial arrangement in a completely randomized design with 450 day-old broilers was conducted to study the effect of energy level and time of change from starter to finisher diets on performance and economic aspects of broilers. Broiler chickens were fed at three levels of dietary energy (2800, 3000, and 3200 Kca1ME/Kg) from 1-42 days of age. Starter and finisher diets were changed at 16, 21, and 26 days of age and then finisher diets were fed up to 42 days of age. The effect of diet energy and changing time from starter to finisher diets on body weight and feed conversion at 26 days of age were significant (P<0.01). By increasing energy level and changing time from starter to finisher diets, at this age, body weight increased and feed conversion ratio decreased. Energy conversion decreased by decreasing the levels of energy content of diet and increasing time of change from starter to finisher diets (P<0.01). At 42 days of age, the effects of diet energy and changing time from starter to finisher diets did not show any significant effects on feed and energy conversion; in contrast, body weight at this age increased significantly as a result of increasing time of change from starter to finisher diets (P<0.05). From 1-42 days of age, the interaction between diet energy and changing time from starter to finisher diets on feed and energy conversion was significant (P<0.05). The results from this study suggest that increasing diet energy and changing time from starter to finisher diets for producing broilers with less than .2 kg will improve their general performance.