Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2010
Publication Date: 3/20/2011
Citation: Rosebrough, R.W., Russell, B.A., Richards, M.P. 2011. Further studies on short term adaptations in the expression of lipogenic genes in broilers. Comparative Biochemistry and Physiology. 59(Part A):1-6.
Interpretive Summary: Excess fat production by the modern broiler chicken presents a two-fold problem. The consumer has health concerns about the link between cardiovascular disease and dietary fat. The producer would like to produce more lean meat rather than fat condemned at the processing plant. Historically shifts in metabolism have resulted in dietary fat being merely shunted to replace that synthesized from other feed ingredients. We have found that altering feeding regimens and dietary crude protein in the broiler will cause permanent changes in fat synthesis and storage, such that dietary fat will not be shunted to body fat stores. The present study was designed to determine if dietary protein elicited changes in intermediary metabolism and if changes resulted from alterations in the expression of genes coding for certain regulatory proteins. Although increasing dietary protein decreased fat synthesis by the broiler, gene expression did not accompany this decrease unless the diet contained a very high level of protein. Modest increases in dietary protein will decrease lipid synthesis without affecting gene expression.
Technical Abstract: This experiment was conducted to determine possible relationships between certain indices of lipid metabolism and specific gene expression in chickens fed graded levels of dietary crude protein. Male, broiler chickens growing from 7 to 28 days of age were fed diets containing 12 or 30% protein ad libitum. Both groups were then switched to the diets containing the opposite level of protein. Birds were sampled at 0, 6, 9, 12, 18 and 24 hr. following the switch in protein levels. Measurements taken included in vitro lipogenesis (IVL), malic enzyme (ME), aspartate amino transferase (AAT) and isocitrate dehydrogenase (NADP) (ICD) activities. In addition, ME, AAT, ICD, fatty acid synthase (FAS), acetyl coenzyme carboxylase (ACC) gene expression rates were determined. IVL and ME activities were inversely related to dietary protein levels (12 to 30% and to acute changes from 12 to 30%. In contrast, expression of ME, FAS and ACC genes were decreased by feeding a 30% protein diet (acute or chronic feeding). Results of the present study demonstrate a continued role for protein in the regulation of broiler metabolism. It should be pointed out; however, that metabolic regulation at the gene level only occurs when feeding very high or very low levels of dietary protein.