Abstract
The decreased vitality of ram and bull spermatozoa caused by sudden cooling (cold shock) may be largely prevented by the presence of egg yolk in the diluent. The activity of egg yolk in preventing cold shock lies in the alcohol-soluble, acetone-insoluble fraction. The phospholipid, lecithin, may be isolated from this and it will prevent cold shock in concentrations as low as 0.12%. The protective action of lecithin for ram spermatozoa is greater at pH 6.5 than at a neutral or alkaline pH.