ON DEEP FREEZING OF BOAR SEMEN - INVESTIGATIONS ON THE EFFECTS OF DIFFERENT STRAW VOLUMES, METHODS OF FREEZING AND THAWING EXTENDERS

At the Bundesanstalt Wels tests with frozen-thawed boar semen in plastic straws were conducted. The influences of straw volume, method of freezing and thawing extender were investigated. The straw volumes of 1,0 and 0,5 ml showed significantly better thawing results in a preliminary trial than the 5,0 ml Macrotub. When semen was frozen in a computerized freezer with automatic seeding, all tested straw, volumes gave significantly better results than the straws frozen in static N2-vapor. A ready to use commercial extender was used for thawing with good results to simplify the handling of deep frozen semen for on farm insemination. In the main trial 60 ejaculates from 10 boars were frozen in 1,0 ml straws in the computerized freezer. Three in vitro parameters for fresh semen (motility, osmotic resistance and keeping quality under standard conditions) and two parameters for thawed semen (motility and percentage of sperm with normal apical ridge) were recorded and correlated. The osmotic resistance test proved to be well suited as means of predicting the fitness of an ejaculate for deep freezing, but the other two fresh semen parameters showed poor correlation with the parameters for thawed semen. From the parameters for thawed semen a freezing score was derived as a measure of the freezability of single ejaculates and boars. A preliminary insemination trial gave satisfying farrowing rates.