Effect of Season, Sex and Breed on the Thyroxine Secretion Rate of Beef Cattle and a Comparison with Dairy Cattle

Abstract
Two hundred ninety-six observations of the thyroxine secretion rate (TSR) were made on 68 heifers, 33 steers and 74 bulls of the Angus, Shorthorn and Hereford breeds during various months of the year. No significant differences were found due to sex, castration, breed, or season. Individual variations ranged from 0.1 to 0.7 mg. of 1-thyroxine, while the mean TSR was 0.27±.006 mg. per 100 lb. body weight. This value is significantly lower than that reported for dairy cattle (0.40±.013). Copyright © 1963. American Society of Animal Science . Copyright 1963 by American Society of Animal Science