Lipogenesis of Fasted-refed Chicks as Influenced by Dietary Protein Levels

Abstract

The effects of fasting-refeeding and dietary protein level on the hepatic lipogenesis of growing meat-type birds, were investigated. All the birds were fasted continuously for 4 consecutive days and then refed for 1 day, 2 days and 4 days with diets containing normal (21%), low (12%) and high (30%) levels of dietary protein. Four days of fasting greatly reduced body weight and a similar length of refeeding, regardless of protein level, proved insufficient to recover the lost weight. Liver weight responded positively to refeeding with the low-protein group registering the highest score.
Among the lipid fractions determined, triglyceride demonstrated the most dramatic increase that was inversely proportional to the dietary protein level, Serum cholesterol, NEFA and β-lipoprotein tended to show the same reaction, i. e., higher values were obtained when the protein level was low. Worth noting was the serum cholesterol score for the 30% group which significantly decreased as protein level increased thereby suggesting the hypocholesteremic influence of high protein levels in the diet.
In almost all the parameters that positively responded to both refeeding and the protein content of the diet, the response was such that an increase-decrease pattern was established whereby the highest increase emerged on the 2nd day of refeeding, then tapered off on the 4th day to a level that was still greater than the 1st-day refeeding value. Further, that lipid biosynthesis was greatly enhanced when the protein level was low could probably be ascribed to the increased carbohydrate content of such low protein diets which in turn provided a ready supply of glucose that accelerated the production of acetyl-CoA, thus favoring the formation of large quantities of reducing equivalents which have been implicated to be the limiting factor in fatty acid biosynthesis.