Growth characteristics of the Ross 708 broiler chicken.

A growth trial was conducted with the Ross 708 broiler chicken to corroborate the relationships between changes in the growth curve (7 to 35 days) and in vitro metabolic parameters. These in vitro parameters also included estimates of the expression of certain genes regulating proteins implicated with regulation of lipogenesis. Birds were fed diets containing 24% protein from 0 to 14 days of age, 21% from 14 to 26 days of age and 18% protein until 35 days of age. Birds were selected and killed at ages corresponding to protein changes. Dual X-ray absorptiometry (DXA) was used to approximate body composition of birds at day 35. The switch from the starter protein level of 24% crude protein to the only slightly lower protein grower diet (21% crude protein) increased both in vitro lipogenesis and malic enzyme activity. A similar observation was noted when the birds were switched to the 18% crude protein finisher diet. These same switches also elicited initial increases in malic enzyme, fatty acids synthase and acetyl CoA carboxylase gene expression that were not sustained following adaptation to the dietary change. Data also show that DXA can be used to estimate body composition of this type of bird.