PRESERVATION OF EJACULATED AND EPIDIDYMAL STALLION SPERMATOZOA BY COOLING AND FREEZING

The suitability of ejaculated and epididymal stallion spermatozoa for cooled storage (5 degrees C) and cryopreservation was examined in 5 ej aculates from each of 6 stallions and in spermatozoa recovered from th e cauda epididymidis after castration of these stallions. The percenta ge of progressively motile spermatozoa, examined by subjective estimat ion (cooled samples) or by computerized analysis (frozen-thawed sample s), was used as parameter. In ejaculated semen samples containing 5 an d 25% seminal plasma in a skim milk glucose extender, the lower amount of seminal plasma supported spermatozoal motility significantly bette r throughout storage at 5 degrees C. Addition of 5 or 25% seminal plas ma to perfused epididymal spermatozoa (0% seminal plasma) resulted in a significant stimulation of spermatozoal motility by 25% seminal plas ma at 0 h (P < 0.05) and to a lesser extent at 24 and 48 h. Post-thaw motility of ejaculated as well as epididymal spermatozoa was not influ enced by slow cooling to 15 degrees or 5 degrees C with or without gly cerol prior to rapid freezing in liquid nitrogen vapor. During cooled storage, seminal plasma had a stimulatory effect on epididymal spermat ozoa and depressed motility in ejaculated spermatozoa. Results on cryo preservation indicate that freezability of equine spermatozoa is alrea dy determined when spermatozoa leave the tail of the epididymis.