A comparative study of trout and chicks regarding dietary effects on glycogen concentration in liver and muscle during feeding and subsequent to feed withdrawal.

1. Glycogen concentrations in liver and skeletal muscle were compared in rainbow trout and in chicks of two genetic sources. 2. Tissue glycogen concentrations were determined during feeding and after feed withdrawal in response to diets high in carbohydrate and oil, respectively. 3. Livers of trout and chicks were heavier and glycogen concentrations were higher in both liver and muscle of trout and chicks fed high-carbohydrate diets. 4. Feed withdrawal resulted in gradual but steady declines in trout glycogen over a 16-day period but caused sharp declines in liver glycogen in chicks followed by a rebound and a more gradual decline within a 5-day period. 5. Feed withdrawal from trout caused declines in muscle glycogen followed by rebounds which occurred more rapidly when the high-carbohydrate diet had been fed. 6. Feed withdrawal had little effect on muscle glycogen in broiler-type chicks. In White Leghorn chicks there was a general decline in muscle glycogen which showed marked fluctuations when the high-fat diet had been fed.