pharmaceutical preparations in dosage forms and animal feeds consisting essentially of compatible , pharmaceutically acceptable carriers , oral and injectable , compounded with a sub - lethal , yet effective , amount of epichlorohydrin for inducing sterility in male mammals . methods for preventing impregnation of females by male mammals which comprises administering systemically to male mammals a sterilizing amount of epichlorohydrin , also identified as γ - epichlorohydrin .