the effect of zinc nano-particles (zn- nano- complex) on bull sperm quality after freeze-thawing process studied. ejaculates collected from four holstein bulls twice a week. on the day of semen collection, four ejaculates were pooled and diluted with bioxcell extender containing 0, 10-6, 10-5, 10-4, 10-3, 10-2 molar of zinc nano-complex and frozen. after thawing, sperm motility and motion param...