STUDIES ON THE ABSENCE OF GLYCEROL IN UNFROZEN AND FROZEN RAM SEMEN - DEVELOPMENT OF AN EXTENDER FOR FREEZING - EFFECTS OF OSMOTIC-PRESSURE, EGG-YOLK LEVELS, TYPE OF SUGARS, AND THE METHOD OF DILUTION

Four experiments were conducted to study the effects of: (1) osmolality (275 to 500 mOsm at 25-mOsm increments); (2) egg yolk levels (0 to 40% at 5% increases); (3) 10 sugars, 10% ( v v); and (4) two different dilution methods (soon after collection at 37 °C or after cooling to 5 °C) on percentage of motility of spermatozoa before freezing and on frozen-thawed ram spermatozoa diluted in TEST [Tes (N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid) titrated with tris(hydroxymethyl)aminoethane to a pH of 7.0]. Glycerol was not used in any of the experiments. Before freezing, ram semen cooled to 5 °C, held for 3 h after collection, and then diluted with TEST buffer at 300-375 mOsm and 25-40% egg yolk ( v v) had the best progressive motility. Overall, the presence of 10% of any sugar ( v v) did not significantly affect the motility of spermatozoa before freezing. Maximum post-thaw motility was obtained when ram semen was diluted cold at 5 °C 3 h after collection in TEST buffer, pH 7.0, 375-400 mOsm, with 25-30% egg yolk ( v v) and 10% maltose monohydrate ( v v). © 1991.