The Effect of Prolonged Feeding of Thiouracil on Testicular Development in Japanese Quail

Abstract

The effect of 0.2 percent dietary thiouracil from day of hatch through 54 days of age on testicular development and age at sexual maturity was investigated in two lines of Japanese quail. Prior to this experiment, one line (T) had undergone 18 generations of selection for increased 4-week body weight under a 20 percent protein diet containing 0.2 percent thiouracil. The second line (C) had been maintained on a 28 percent protein diet (“normal” diet) as a non-selected control. Body, thyroid and testes weights were measured at 4-day intervals beginning at 38 days of age through 54 days of age. Thyroids were sectioned and examined microscopically to determine follicle size and height of the secretory epithelial cells lining the follicles. Testes were sectioned and examined microscopically to determine the degree of spermatogenic development.Thiouracil (0.2 percent) in the diet of C-line males retarded testicular development as indicated by reduced testes weight and on additional time period of 8 to 12 days required to reach sexual maturity. In comparison, no apparent delay in sexual maturity was evident in T-line males receiving the same dietary amount of thiouracil. Mean thyroid weight, thyroid follicle size and height of secretory epithelium were all significantly greater in C-line males receiving dietary thiouracil than in T-line males. The experimental evidence thus indicates that T-line males selected for increased 4-week body weight in the presence of a goitrogenic challenge for 18 generations have developed an ability to resist the retarding influence of the goitrogen on reproductive efficiency.