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The Nutritional Requirements of the Protein-Depleted Chicken

I. Effect of Different Protein Depletion Regimes on Body Composition During Depletion, Repletion and Redepletion¹

Department of Poultry Science, Rutgers—The State University, New Brunswick, New Jersey

Three groups of growing chickens were depleted to two thirds of their starting body weight by (a) complete starvation, (b) feeding a nitrogen-free diet, and (c) feeding a gelatin-containing diet. They were then repleted to their starting body weight and to twice the initial body weight. Finally they were starved for a 6-day period. Carcass and liver composition analyses were carried out at each interval for each of the three treatment groups as well as for a control group of chicks that received a standard ration throughout except for the final period when they too were starved.

1. During initial depletion chicks in the nitrogen-free group lost the greatest amount of carcass nitrogen but simultaneously increased in carcass and liver fat compared with the other treatments. Collagen content did not decrease during initial depletion on any regime.

2. On repletion to the starting weight, there was a lag in carcass nitrogen accretion in all treatment groups compared with the nondepleted controls. A similar but more pronounced lag occurred in collagen growth during the repletion period. By contrast, the liver nitrogen increased over threefold compared with that of the control animals for the same period.

3. On repletion to twice the starting weight the body composition of all 4 groups was essentially the same.

4. During the redepletion-by-starvation period, chicks in the previously-starved group lost more carcass nitrogen than those in either the control or the other two treatment groups. On the other hand, the nitrogen-free group conserved body nitrogen, as shown by a loss in carcass nitrogen that was only half that of the previously-starved group. In contrast with the unchanged collagen content of the carcass during the initial depletion period on all regimes, there was a loss of 20% of collagen during final starvation.

Manuscript received 18 May 1960.