Influence of diet and feeding technique on growing, feed conservation ratio and carcass composition for fast- and slow-growing broiler chickens

The present study was focused on the observation of the growth performance of fast- (strain ROSS) and slow(strain ISA) growing broiler chickens in dependence on ad libitum or restrictive feeding and on different intensities of nutrition. Influences on carcass quality were investigated at 35 and 56 days of age. Digestibility of nutrients and of energy was determined at 3 and 8 weeks of age. Feed intake was lower in ISA-broilers in comparison to ROSS-broilers independent of feed. Body weight gain was 1950 g for ROSS-broilers and 1467 g for ISA-broilers fed ad libitum at 35 days of age. Body weight gain was 2462 g for ROSS-broilers and 2226 g for ISA-broilers fed restrictive feed at 56 days of age. The growth data was adapted on the basis of the Gompertz function. Maximum daily weight gain was reached by ROSS-broilers at 28-34 days of age and by ISA-broilers at 32-39 days of age. The extension of the growing period from 5 to 8 weeks increased meat (breast, thigh) mass by 40-50 % in all broilers. Feed restriction reduced muscle mass by 25 %. Digestibility of crude protein was higher by ISA-broilers then by ROSS-broilers. The concentration of N-corrected convertible energy (AMEN) content was 1 MJ higher in conventional diets for fast growing broilers as the alternative feed.