Author
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Rosebrough, Robert |
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Submitted to: European Association of Animal Production Proceedings
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/5/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Excess fat production in the modern broiler accounts for an annual loss to the poultry industry of 800 to 950 million dollars. The original source of this problem relates to selection genetic practices that emphasized rapid growth at the expense of other carcass characteristics. The literature is of limited value in determining methods to depress fat synthesis and allow lean tissue synthesis to remain at an elevated rate. Catecholamine turnover constants were developed for dopamine (DA) and norepinephrine (NE) in various organs of the broiler. These constants indicate a more rapid rate of catecholamine turnover in mammals than in chickens. Moreover, DA turnover in chicken brain is more rapid than NE turnover in that same organ. Fractional NE turnover in brains of fed and fasted chickens were similar. DA turnover was much greater than NE. The value to the chicken of increased norepinephrine as a function of high-carbohydrate diets probably lies in the ability of these kinds of diets to stimulate fat synthesis. If pancreatic glucagon can be shown to be under the influence of the SNS, the lipolytic characteristics of this hormone may be a natural feedback on the production of excess fat in chickens fed high-carbohydrate diets. Unlike mammalian liver tissue, the avian liver may not respond to the hormone insulin but is more responsive to the catecholamine family of hormones. Catecholamines are of importance because of the ability of these hormones to cause a referential change in the broiler carcass such that the end product contains less fat and more muscle. Technical Abstract: Indian River male broiler chickens growing from 7 to 28 d of age were fed diets containing 120, 210 and 300 g crude protein and 0, 1.7 or 16.7 g of added tryptophan (TRP)/kg diet. Heart, brain and pancreatic norepinephrine NE, dopamine DA, serotonin 5-HT and 5-hydroxy-ind acid 5-HIAA concentrations were determined by HPLC. Feed intake was depressed by feeding diets containing 120 g and 16.7 g added TRP/kg compared to this level of crude protein but lower levels of TRP. Additional dietary TRP had no effect on enzyme activities. The lowest cardiac NE and DA concentrations were noted in chickens fed the lowest level of crude protein. Additional dietary Trp increased cardiac NE and DA. The greatest pancreatic NE concentrations were noted in chickens fed the lowest of crude protein. The diet containing 120 g crude protein and 16.7 g TRP/kg increased brain 5-HT and 5-HIAA compared to the other treatments. These two amines were only marginally changed by the other dietary treatments, an observation paralleling feed intake data. Feed intake of chickens fed very low crude protein may be affected by TRP through the influence of 5-HT. |
