Author
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Rosebrough, Robert |
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Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/12/1999 Publication Date: N/A Citation: N/A 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 which is condemned at the processing plant. Adding dietary fat to the broiler diet will depress the ability of the chicken to synthesize fat from dietary carbohydrate and protein sources. Historically this shift in metabolism has resulted in dietary fat being merely shunted to replace that synthesized from other feed ingredients. We have found that altering the thyroid axis in the broiler will cause permane changes in fat synthesis and storage, such that dietary fat will not be shunted to body fat stores. The present study demonstrates that graded leve of dietary did depress fat synthesis in the broiler. Adding thyroid hormone to the diets also depressed fat synthesis regardless of dietary fat levels. .This study further indicates that both dietary fat and thyroid hormones change avian lipid metabolism. This finding is opposite to that noted in mammals. Cost-benefit data must be derived for each producer before a blank recommendation can be made for high fat diets for broilers. Technical Abstract: Male, Indian River, broiler chickens growing from 7 to 28 d were fed on diets containing 180 g crude protein, 1.25, 2.5 or 5.0 MJ fat calories and O or 1 mg T3/kg diet. Birds were bled and sacrificed at d 28, 29 and 30. Measurements taken at these intervals included in vitro lipogenesis (IVL), growth and feed consumption and hepatic enzyme activities. Plasma metabolites as well as thyroid hormones were also determined. Dietary fat levels did not influence growth or feed intake. In contrast, T3 decreased growth and feed intake by 25% without altering the efficiency of feed utilization. Dietary T3 and additional fat decreased IVL and lipogenic enzyme activities. Dietary T3 increased plasma T3 and decreased plasma T4. Dietary energy source had no effect upon plasma thyroid hormone levels. Although both additional dietary fat and T3 modify broiler lipid metabolism, there was no additional treatment effect when high-fat diets were supplemented with T3. In contrast to previous reports, T3 did not increase any parameter associated with lipid metabolism. |
