The effect of busulfan treatment on endogenous spermatogonial stem cells in immature roosters.

Several methods have been developed for suppression of endogenous spermatogenesis in recipient males before spermatogonial stem cells transfer. Currently the chemical treatment with alkylating agent busulfan is the method of choice in mammals. Still, in different mammalian species wide variability in optimal doses of busulfan has been demonstrated, whereas in birds, the dosage has not yet been optimized. We tested the sterilizing effect of several busulfan doses: 20, 40, and 60 mg/kg of BW as a single or double intraperitonial injections in pubertal-age roosters. It was found that the 20 to 40 mg/kg of BW doses effective in mice did not lead to suppression of spermatogenesis in birds. A single high dose of busulfan (60 mg/kg of BW) resulted in the death of all treated chickens, whereas the same amount of busulfan applied in 2 doses resulted in considerable suppression of spermatogenesis in majority of treated birds. Application of busulfan in several doses also caused less physiological stress than single-dose application.