The Effects of Certain Estrogenic Hormones, Terephthalic Acid and Calcium Level upon Oxytetracycline Utilization

LOWERING of the dietary calcium level (Price and Zolli, 1959), addition of terephthalic acid (TPA) to the diet (Peterson, 1958) or injecting chicks with estradiol (Harms et al., 1963), have been reported to increase the antibiotic content of blood serum. Harm s et al. (1963) also reported that these methods of increasing serum antibiotic level were additive. The studies reported herein were conducted to determine the effect of administering estrogenic hormones upon the oxytetracycline (OTC) content of blood serum of chicks, and to determine whether the response from the estrogenic hormone dienestrol diacetate was additive to the response from lowering dietary calcium level and/or supplementary TPA. Five-week old broiler-type chicks, which had been receiving a diet containing one percent calcium (Table 1) since day of age were used in these studies. At the beginning of each experiment three males and three females were randomly alloted into each pen…