Published online by Cambridge University Press: 09 March 2007
Indian River male broiler chickens growing from 7 to 30 d of age were fed on diets containing crude protein levels ranging from 120 to 3041 g/kg plus 0 or 1 mg triiodothyronine (T3/)kg diet. The purpose of this study was to examine the effects of these treatments on lipogenesis after a common diet was fed (180 g crude protein/kg diet from 30 to 56 d of age). Dietary treatment groups were sampled at 30 and 56 d. In vitro lipogenesis was determined by incubating liver explants for 2h at 37°in Hanks' salts containing 25 mM-HEPES and 10 mM-[2-14C]acetate and then measuring acetate incorporation into total lipid. Growth and feedconsumption from 7 to 30 d increased (P<0·01) as dietary protein increased from 120 to 210 g/kg diet. Both measurements decreased as crude protein increased from 210 to 300 g/kg diet.T, decreased (P<0·01) growth and feed intake during this period.Low-protein (<180 g/kg) diets increased (P<0·05) and T3, decreased lipogenesis in 30-d-old chickens. Although birds given T3from 7 to 30 dgrew at the greatest rate from 30 to 56 d of age, the final body weight was still less than controls.In vifm lipogenesis at 56 d of age was not affected by either of the two dietary treatments. In contrast, the relative size of the abdominal fat pad (g/kg body weight) at 56 d was decreased by feeding T3from 7 to 30 d. Any changes in metabolism elicited by either dietary protein levels or hormone treatments may be specific to the particular dosing interval and are not sustained when acommon diet is fed during a repletion period.