Fertility of Chickens Fed Thiouracil Prior to Maturity

MARKS and Lepore (1968) observed that Coturnix fed diets containing thiouracil during the growing period had higher fertility than nontreated controls. Shaffner and Andrews (1948) reported that fertilizing capacity of spermatozoa was adversely affected by feeding cocks thiouracil. Contrariwise, the addition of thiouracil to the diet of laying hens had no adverse effect upon fertility and hatchability (Andrews and Schnetzler, 1945; McCartney and Shaffner, 1950). The thyroid gland has been shown to influence ovarian function and reproduction in other species (Weichert, 1930; Jones et al., 1946; Ershoff, 1945). Kraatz (1939) observed larger litters from rats fed a thyroid substance prior to the first estrous cycle and suggested that hyperthyroidism stimulates the release of the luteinizing hormone. Petersen et al. (1952) reported that hyperthyroidism, produced by thyroxine injection, increased the number of guinea pigs born alive. The current investigation was conducted to obtain additional information on the possible interrelationship of thyroid…