Family Differences in Tolerance to High Levels of Protamone

THE reports of feeding thyroprotein to chickens and its effect on growth are not consistent. It is not the objective of this paper to review all those results in detail but it should be mentioned that the level of thyroprotein fed, age of birds, and the season of the year are among the factors that account for the inconsistency in the results of the different investigators. Turner et al. (1944), Glazener et al. (1949), and Boone et al. (1950) found that when high levels of thyroprotein were fed, a marked decrease in the rate of growth was observed. Irwin et al. (1943) reported that severe mortality occurred when high levels of thyroprotein were added to the ration. The objective of this investigation was to determine if there are sire and dam family differences in tolerance of chicks to toxic levels of Protamone and to study the effect of high levels . . .