Interference by Glycerol with Differential Staining of Bull Spermatozoa as Used with Semen Thawed from the Frozen State

Abstract

The relative usefulness of 2 measures of spermatozoan viability (per cent of motile spermatozoa and per cent of live spermatozoa as determined by differential staining) was studied on frozen semen, using 3 semen diluters containing varying levels of glycerol. One semen diluter was composed of 20% of egg yolk and 80% of a 3% aqueous solution of sodium citrate dihydrate, the other 2 being boiled skimmilk and boiled homogenized milk. Glycerol levels, as used with the 3 diluters, varied from 2.5 to 12.5%. Results indicated that as the levels of glycerol in the diluters exceeded 4%, the per cent of live spermatozoa decreased in a very disproportionate manner to the per cent of motile spermatozoa, and predicted per cent of live spermatozoa, becoming extreme at the high levels of glycerol. A plausible explanation of these observations is that the higher levels of glycerol increased the permeability of the living and motile sperm cells to the stain, allowing some of them to be counted as dead cells in the differential staining procedure. The per cent of motile spermatozoa is judged to be the better measurement of spermatozoan viability in studies involving the use of glycerol as a constituent of semen diluters.