Author
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Rosebrough, Robert |
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Mitchell, Alva |
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Submitted to: Feedstuffs
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/1/2006 Publication Date: 12/1/2006 Citation: Rosebrough, R.W., Mitchell, A.D. 006. A genetic component to the normal growth of the Ross 708 broiler chicken. Feedstuffs. 78 (46) 26-28. Interpretive Summary: The Ross 708 is an example of the modern broiler chicken bred for rapid growth and body size. The bird is appropriate for both the whole broiler and roaster carcass markets. The challenge in raising this bird is to maximize its growth potential, lean tissue deposition and minimize excess fat accretion. As such, the role of dietary protein in meeting growth and lean tissue parameters for this bird has not been described from a biochemical standpoint. It is well known that the quantity (crude protein concentration) and quality (amino acid composition relative to the required balance) of the dietary protein affect the body composition of chickens. 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. Changes in the expression of certain functional gene groups appears to be a normal part of the protein feeding regimen followed by the poultry industry. Technical Abstract: A growth trial was conducted with the Ross 708 broiler chicken to corroborate the relationships between changes in the growth curve (7 to 35 days) and in vitro metabolic parameters. These in vitro parameters also included estimates of the expression of certain genes regulating proteins implicated with regulation of lipogenesis. Birds were fed diets containing 24% protein from 0 to 14 days of age, 21% from 14 to 26 days of age and 18% protein until 35 days of age. Birds were selected and killed at ages corresponding to protein changes. Dual X-ray absorptiometry (DXA) was used to approximate body composition of birds at day 35. The switch from the starter protein level of 24% crude protein to the only slightly lower protein grower diet (21% crude protein) increased both in vitro lipogenesis and malic enzyme activity. A similar observation was noted when the birds were switched to the 18% crude protein finisher diet. These same switches also elicited initial increases in malic enzyme, fatty acids synthase and acetyl CoA carboxylase gene expression that were not sustained following adaptation to the dietary change. Data also show that DXA can be used to estimate body composition of this type of bird. |
