Preservation of fowl semen in liquid nitrogen—an improved method

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Abstract
An improved method of storing fowl semen in liquid N is described. It uses glycerol as a cryoprotectant, and the degree of fertility obtained with semen stored for up to 2 1/4 yr is very promising. The essential features of the method are a slow freezing rate, a reduction of temperature to -35.degree. C before the semen is plunged into liquid N and insemination within 15 min of thawing and removing the glycerol from the diluent. Further improvements in the technique may be expected through better control of the injection of liquid N into the freezing chamber, thereby minimizing localized, rapid temperature changes around the ampoules during freezing. Preliminary results suggest that it may prove possible to select males for the ability of their spermatozoa to withstand freezing. The importance of recognizing differences between males in the initial quality of semen and between females in the physiology of the reproductive organs in determining the fertilizing ability of stored semen is discussed.