Comparative Response of Chicks and Rats to Dietary Thyroactive and Antithyrotoxic Supplements

Abstract

Chicks and rats were compared in their response to dietary thyroprotein and liver supplements. The addition of high levels of thyroprotein to casein-glucose diets reduced weight gain and decreased survival time of growing chicks and albino rats. Concomitant supplementation with liver partially prevented growth depression and increased survival time.Heart and kidney weights of chicks were increased by thyroprotein and decreased by liver supplements. Liver weights appeared to be similarly, but less dramatically, affected. Spleen weights were generally reduced by thyroprotein and increased by liver while effects of thyroprotein on thymus weights were variable and inconclusive.In chicks fed thyroprotein supplements, oxygen consumption rates decreased rapidly after the initiation of fasting and were equal or slightly below euthyroid controls after 24 hours. In non-fasted chicks and rats, oxygen consumption was increased by thyroprotein and the addition of liver to thyroprotein supplemented diets partially prevented the increase in oxygen consumption. However, liver supplementation did not affect the endogenous metabolic rate of chicks. It appears that similar mechanisms are involved in the antithyrotoxic response of the two species.