Author
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Rosebrough, Robert |
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Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/7/1994 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 annually. 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. A strain of male chickens noted for its rapid growth was used to study the effects of implantation with the male hormone, testosterone and triiodothyronine on the ability of chicks to synthesize fat. The line of chicks selected for rapid growth provided liver tissue that, when put into a culture system, exhibited a high rate of lipid synthetic ability. When lines of chickens were fed higher protein diets, they exhibited a decrease in the ability to produce fat. Likewise, including the hormone triiodothyronine in the diets also decreased fat synthesis. These regimens may be of value if the slight growth-depressing effect of triiodothyronine can be overcome. Technical Abstract: Thirty-two chickens were implanted with 0 or 50 mg and fed diets containing 0 or 0.1% propylthiouracil for 14 days to determine regulation of energy metabolism in the normal and hypothyroid chicken. In vitro lipogenesis was measured in liver explants. Liver glycogen and plama metabolites were also measured. Controls were the largest (p<0.05) while euthyroid chickens implanted with testosterone were the smallest. All combinations of treatments increased liver glycogen compared to controls. Plasma triglycerides were increased (P<0.05) by hypothyroidism (feeding propylthiouracil). In contrast, the combination of hypothyroidism and testosterone implantation gave plasma triglycerides similar to controls. Hypothyroidism increased (P<0.05) in vitro lipogenesis. Again, the combination of hypothyroidism and testosterone implantation gave values similar to controls. Generally, the effects of testosterone are far less noticeable than are the effects of the female hormone, estradiol. |
