Tyrosine, Protein and Ascorbic Acid Effects on Egg Shell Thickness from Chickens Subjected to Heat Stress

REVIEW OF LITERATURE EARLIER it was observed that hens subjected to heat stress appeared to respond favorably to dietary ascorbic acid supplementation in maintaining egg shell thickness when a ration containing 13 percent protein was fed, but not at a 17 percent level (Thornton, 1960). Since all ingredients of those rations were similar with the exception of the corn, milo and soybean oil meal ratio, it seemed probable that the lack of response to ascorbic acid at the higher level may have been due to differences in dietary content of specific amino acids. On calculation it was noted that while the protein ratio of the 13 percent level to the 17 was 0.765, the ratio of tyrosine for the two diets was 0.838 and the phenylalanine and tyrosine levels combined were 0.799. Despite the higher percent of tyrosine and phenylalanine per unit of total protein in the 13 percent diet, …