Freezability of Bull Semen in Centrifuged or Dialyzed and Reconstituted Buffered Egg Yolk Extenders

Bull spermatozoa were frozen with equal success in a 0.25 m Tris-buffered extender containing either the supernatant or precipitated portion of centrifuged egg yolk. Washing the precipitate with distilled water to remove additional ions and other water-soluble materials had little effect on the osmotic pressure of the washed egg yolk precipitate reconstituted with Tris, but viability of spermatozoa both before and after freezing was reduced. Egg yolk was dialyzed against distilled water until the Na and K levels were reduced to 12 and 10μg per ml, respectively. Different proportions of dialyzed and non-dialyzed egg yolk were combined with Tris buffer, and sperm cell survival following freezing was higher than in the Tris-yolk control (P