Submitted to: Poultry Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 2, 2005
Publication Date: August 1, 2005
Citation: Rosebrough, R.W., Russell, B.A., Poch, S.M., Richards, M.P. 2005. A further examination of the effect of dietary protein in regulating metabolism in the broiler [abstract]. Poultry Science. 85(Suppl 1):A216. Technical Abstract: Two experiments were conducted with Hubbard x Hubbard broiler chickens to further delineate the role of dietary protein as a regulator of lipid metabolism. In both experiments, birds were fed one of two diets (12 or 30% protein) from 7 to 28 days of age. Likewise, in both experiments, birds were switched to the opposite level of dietary protein. However,in the first experiment, birds were selected and killed at 12, 18 and 24 hr following the dietary reversals. Birds were sampled at 3, 6, 9, 12, 18 and 24 hr in the second experiment. In vitro lipogenesis (IVL) was determined by the incorporation of [14C]acetate into hepatic lipids and was indicative of acetyl CoA carboxylase activity (AcCbx). Activities of certain metabolic enzymes and genes controlling these enzymes (malic enzyme, ME; fatty acid synthase, FAS; isocitrate dehydrogenase, ICD;aspartate aminotransferase, AAT and AcCbx) were also measured. In all experiments switching dietary treatments increased and decreased lipogenesis as birds were switched from 30 to 12% protein and from 12 to 30% protein diets, respectively. The greatest rates of change elicited by either regimen occurred by the first day of each reversal (Exp 1). A further examination (Exp 2) indicated significant changes in IVL 12 hr post reversals. Changes in IVL were correlated to changes in the expression of genes for both FAS and AcCbx. In addition, this observation validated our original hypothesis that IVL approximated AcCbx activity. Changes in gene expression always preceded changes in intermediary metabolism, indicating that responses to dietary protein involved some terations in gene activity. Of the three hepatic enzymes monitored, ME activity most closely followed the rapid changes in IVL. Likewise, ME gene expression was both highly correlated to activity changes and most affected by these dietary reversals.