Influence of Thyroxin on Growth of Chickens

THE ready availability of goitrogenic compounds and iodinated proteins during the past few years has stimulated the interest of workers in the possibility of increasing efficiency of growth and production of poultry and farm animals by means of these compounds. The very extensive literature dealing with this subject has been reviewed recently by Blaxter et al. (1949). The relationships between circulating thyroid hormone and experimental criteria have not been reported in most of these experiments, and it appears evident that information on thyroxin levels in the blood in relation to growth and production would be of value in interpreting the results already obtained and in devising plans for future research. This report is concerned with the influence of a wide range of dosage of synthetic dl-thyroxin upon the growth of chickens lacking thyroids. MATERIALS AND METHODS New Hampshire females delivered in 4 different lots as day old chicks from a . . .