INVESTIGATION OF GENETIC MECHANISMS FOR IMPROVING THE REGULATION OF FEED INTAKE AND NUTRIENT UTILIZATION IN POULTRY
Title: The Role of Feeding Regimens in Regulating Metabolism of Sexually Mature Broiler Breeders
| Ekmay, R - |
| Coon, C - |
| DE Beer, M - |
| Rosebrough, Robert |
| Richards, Mark |
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2010
Publication Date: May 1, 2010
Citation: Ekmay, R.D., Coon, C.N., De Beer, M., Rosebrough, R.W., Richards, M.P., Mcmurtry, J.P. 2010. The role of feeding regimens in regulating metabolism of sexually mature broiler breeders. Poultry Science. 89(6):1171-1181.
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 studied 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.
A trial was conducted to determine the effects of different rearing feed regimens on plasma hormone and metabolite levels and hepatic lipid metabolism and gene expression on sexually mature broiler breeders. Cobb 500 birds were divided into two groups at 4 weeks of age and fed either everyday (ED) or skip-a-day (SKP). At 168 days of age, all birds were switched over to an ED regimen. At 185 days (26 weeks) of age, 28 ED-reared and 28 SKP-reared sexually mature breeder hens were randomly selected and sacrificed at intervals after feeding. Liver and blood samples were collected and analyzed. The overall means of glycogen and liver fat % did not differ between feeding regimens; however, glycogen, total liver fat, and liver fat % increased upon feeding regardless of treatment. Relative liver weight increased only in SKP birds. The overall mean gene expressions for isocitrate dehydrogenase, aspartate amino transferase, malic enzyme and fatty acid synthase were not significantly different between treatments although ACC was higher in the ED regimen (p=0.0754). Corticosterone and IGF-2 levels were significantly higher (P<0.05) in SKP birds. SKP birds also had concentrations of leptin, glucagon, and T3. The increase in leptin is a reversal of what was reported during the rearing phase and may pertain to a possible reproductive role. No differences were noted between regimens for the genes controlling lipoproteins (apo B, apo VLDL-II, and FABP); however, apo A1 was significantly higher in the ED regimen (p=0.0016). In summary, different feeding regimens alter metabolic responses which carry over into sexual maturity and exhibit metabolic memory.