Author
 |
Rosebrough, Robert |
|
Submitted to: Nutrition Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/25/1999 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. Historically shifts in metabolism have resulted in dietary fat being merely yshunted to replace that synthesized from other feed ingredients. 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 demonstrates that dietary protein levels do not measurably affect the response of broilers to bouts of fasting-refeeding. This study further indicates that both dietary protein levels and feeding regimens change avian lipid metabolism. This finding is opposite to that noted in mammals. Cost-benefit data must be derived for each producer before a blanket recommendation can be made for altering diets to accommodate metabolic modifiers. Technical Abstract: Seven-day old Shaver broilers were fed diets containing either 120 or 300 g crude protein on either free choice basis or on 7 cycles consisting of 1 day of fasting followed by 2 days of feeding. Birds fed free choice were subjected to the above regimen, but only for one cycle. Birds were bled and killed on day 1, 2 & 3 of the final cycle for each of these experiments. Measurements taken at these intervals included in vitro lipogenesis (IVL), growth and feed consumption, hepatic enzyme activities and plasma triiodothyronine (T3, and thyroxine (T4). Birds fed the lower level of crude protein free choice from 7 to 28 d ate less, were smaller and less efficient in growth. De novo lipogenesis and plasma T3 were greater and T4 was less in birds fed the lower protein diet. Birds cycled through repeated bouts of fasting-refeeding exhibited striking changes on each day of the cycle. The lowest rate of IVL was noted following a 1 day fast and the greatest after 2 day of refeeding. This pattern was noted in birds fed diets containing either 120 or 300 g crude protein/kg although the responses were exaggerated in birds fed the lower level of protein. Chickens fed a low-protein diet in conjunction with a single bout of fasting-refeeding exhibited responses that were similar to chronic bouts of fasting-refeeding. The magnitudes of fasting-refeeding responses were magnified by repeated bouts. Feeding a high level of protein modified some of the effects of a single bout of fasting-refeeding. |
