Correlations of organ weights, hematocrit, and testosterone with sexual maturity of the male turkey.

A study was conducted with Large White breeder male turkeys to determine changes in blood constituents and organ weights associated with sexual maturity. Testicular samples from 8- to 32-wk-old turkeys were histologically examined and the changes in the seminiferous tubule epithelium associated with sexual maturity were correlated with changes in blood constituents and organ weights. Spermatozoa were first found in the lumina of the seminiferous tubules at 15 wk, and semen containing mature spermatozoa was first observed in the ductus (d.) deferens at 26 wk. Testes weights increased significantly between 20 and 22 wk and continued to increase until 30 wk of age. Testosterone concentration in the blood was .2 ng/mL at 16 wk, and steadily increased to 1.3 ng/mL at 34 wk. The increase in testosterone paralleled the increase in testes weights. The bursa of Fabricius weight reached a maximum at 16 wk, began to regress at 22 wk, and was completely regressed at 32 wk. Hematocrit values started to increase at 16 wk and reached a plateau at 22 wk. The association of the increase in hematocrit with the functional maturation of the testes suggests that the increase in hematocrit could be used to predict maturation of testicular spermatozoa in the male breeder turkey. However, semen production (semen accumulation in the d. deferens) did not start until 10 wk after mature spermatozoa were found in the testes.