Increased germ cell loss rates and poor semen quality in stallions with idiopathic testicular degeneration

Five mature stallions with poor semen quality were tentatively diagnosed as having testicular degeneration of unknown cause. Testis samples from these five stallions, and from three mature stallions with normal semen quality, were obtained by castration and prepared for histomorphometry. Increased g erm cell loss rates during late meiosis and spermiogenesis occurred in the stallions with idiopathic testicular degeneration. Poor semen quality, repr esented by a low percentage of morphologically normal, progressively motile sperm in ejaculates, appeared to be a good predictor of testicular degener ation in these stallions.