|DE BEER, M|
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2007
Publication Date: 7/1/2007
Citation: de Beer, M., Rosebrough, R.W., Russell, B.A., Poch, S.M., Richards, M.P., Coon, C.N. 2007. An examination of the role of feeding regimen in regulating metabolism during the broiler breeder grower period. 1. Hepatic lipid metabolism. Poultry Science. 86:1726-38.
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 in meat type chickens. The broiler breeder producer is concerned about the relationship between excess body fat and reproductive inefficiencies during period leading up to the egg-laying period. The latter condition was studies in broiler breeder candidates raised to sexual maturity. Candidates were raised under two regimens: 1) feed allowed every day and 2) feed allowed every other day to restrict total feed intake. Restricting feed, followed by access to feed produced a syndrome similar to that seen in younger birds subjected to fasting-refeeding. Furthermore, this management regimen also caused excess liver fat accumulation and a potential for fatty liver hemorrhagic syndrome and death. Enzyme activity of certain rate limiting pathways reflected noted changes in gene expression and show the potentially significant impact of feeding regimens on gene expression in breeder pullets. In addition, these data should allow broiler breeder producers to design management regimens to maximize the health of breeder candidate hens.
Technical Abstract: A flock of 350 Cobb 500 breeder pullets was divided in two at 4 weeks of age and fed either everyday (ED) or skip-a-day (SKIP) from 4 to 16 weeks of age. Total feed intake did not differ between the two groups. At 112 d, 52 randomly selected pullets from the larger flock of ED fed pullets and 76 from the SKIP fed pullets were individually caged and fed a meal of 74 g (ED) or 148 g (SKIP), respectively. Four pullets from each group were sacrificed at intervals after feeding and livers were collected, weighed and snap frozen for determination of lipogenic gene expression. Total RNA was isolated from livers using Trizol reagent and quantitatively measured by noting the OD 260/280 ratio and qualitatively by gel electrophoresis. The expressions of certain regulatory genes in metabolism (acetyl CoA carboxylase, ACC; fatty acid synthase, FAS; malic enzyme, ME; isocitrate dehydrogenase; ICDH and aspartate aminotransferase, AAT) were determined by real-time RT-PCR. Remaining liver portions were assayed for ME, ICDH and AAT activities as well as for glycogen and lipid content. Liver weight was higher in SKIP than ED birds. Feeding caused dramatic increases in liver weight of SKIP birds, as well as liver glycogen and lipid. Expression of ACC, FAS and ME genes were increased in SKIP birds 12 and 24 hr after feeding, with the increases in ME expression from 0 to 24 hr after feeding being of the greatest magnitude. Enzyme activity of ME, ICDH and AAT was reflective of noted changes in gene expression. In summary, the data presented here show the potentially significant impact of feeding regimens on gene expression in breeder pullets.