Protein Reserves: Evidence for Their Utilization under Nutritional and Disease Stress Conditions

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Abstract
A series of experiments with growing chickens was carried out to evaluate the possible significance of increased body N resulting from a super-normal protein intake. The experimental animals were fed during a preliminary conditioning period either a normal (22%) or a super-normal (28%) protein diet and then subjected to 2 types of stress conditions: 1) they were given a low protein diet deficient in an essential amino acid or a second diet which was further imbalanced through the addition of an amino acid mixture devoid of the same limiting amino acid; and 2) after the birds had been fed the normal and super-normal protein diets for different time intervals, they were inoculated with Newcastle Disease virus and mortality recorded. Parental immunity, as determined from hemagglutination-inhibition titers, was also studied. It was consistently observed that chickens prefed the super-normal protein diet had higher carcass N and gained more weight with the low protein, amino acid-imbalanced rations than did the animals prefed the normal protein diets. The former birds also showed greater parental immunity to and lower mortality from Newcastle Disease virus inoculation. It was concluded that beneficial effects may be realized from protein intakes beyond those necessary for optimal body weight gains.