The Effect of Methods of Adding Egg Yolk and Monosaccharides on the Survival of Frozen Bull Spermatozoa

Summary The inclusion of 25% egg yolk in both the nonglycerol and the glycerol fractions of extenders for frozen semen was compared with including 50% egg yolk in the nonglycerol fraction and none in the glycerol fraction. The final compositions of these two extenders were identical. The average percentages of motile sperm immediately after thawing were 30.5 and 22.3 for the two methods, respectively, and the average 60- to 90-day nonreturn percentages for 1,515 first services were 68.0 and 59.7, respectively. These differences were highly significant statistically (P Fructose, glucose, or xylose was added to give a final concentration of 1.0% by adding the sugar entirely in the nonglycerol fraction, equally in the nonglycerol and glycerol fractions, or entirely in the glycerol fraction. The three methods of incorporating the sugars resulted in 21.6, 28.4, and 28.4% motile sperm, respectively, immediately after thawing. The average percentages of motile sperm in the extenders containing the three sugars were: fructose, 27.9; glucose, 26.4; and xylose, 24.2. In both eases differences were highly significant (P