The effect of genotype on response in body composition to variation in dietary protein : Energy ratios

An experiment with 480 day-old chicks of four commercial strains was conducted to study the effect of genotype on response in body composition to variation in dietary protein: energy ratios. the chicks were randomly allocated into 4x2x4 factorial and fed on a commercial starter diet (250 g cp and 12.5 mj of me /kg) from hatching to 5 d of age and divided into two groups with three replications each of 16 birds and given either the such starter diet (s) or a finisher diet (f) containing 190 g cp and 13.0 mj of me /kg. the birds were reared in strain-and sex-intermingled groups in brooders and followon cages until they reached the target body weight of 600-650 g (females) or 650-700 g (males) and transferred to single cages and fed s or f diet until 1200-1300 g (females) or 1300-1400 g (males). the lighting program was 23 h light for the first two days,and reduced to 18 h/d for the remainder of the experiment. there were considerable variations in relative growth performance,fcr,carcass fat and abdominal fat due to genotypes and dietary regimen. although birds tend to response in similar way when dealing with the excesses and insufficient supply,the nutrient requirements in relation to the protein: energy ratios should be designed according to genetic background. the accumulation of fat during the growing period was primarily due to the genetic variation whereas beyond this age,variation in abdominal fat was due principally to dietary effects. © 2010 diponegoro university. all rights reserved.