Effect of cold shock, liquid storage, and pellet-freezing on successive ram ejaculates

Abstract

(1) Nine successive ejaculates were collected from each of four Merino rams on three occasions at intervals of three days. The mean time intervals between successive ejaculates on the first, second, and third collecting days were respectively 41, 28, and 30 min.

Aliquots from alternate ejaculates (first, third, fifth, seventh, and ninth) were cold-shocked before and after 1 : 4 dilution with an egg yolk–glucose–citrate diluent. Similarly diluted aliquots were stored at +2°C for 16 days and also frozen in pellet form after addition of 6% glycerol to a final 1:8 dilution.

(2) Both undiluted and diluted spermatozoa showed increased susceptibility to cold shock with succession of ejaculates. Egg yolk–glucose–citrate diluent ameliorated the deleterious effect.

(3) There were no marked differences in reanimation at thawing of pellet-frozen successive ejaculates. During a 6 hr incubation of the thawed semen at 37°, however, there were significant ejaculate differences in viability, the ninth collection having the lowest value.

The mean reanimation of pellet-frozen spermatozoa after thawing was 58.7°. During incubation periods of 2,4, and 6 hr at 37°C, 47, 60, and 70% respectively of the original post-thawing motile spermatozoa became immotile.

(4) During storage for 16 days at +2°C, the third and fifth ejaculates gave the best viability values. There were, however, no marked differences between ejaculates during the first 6 days of storage.

(5) No firm relationships were found between cold shock values and subsequent viability during liquid storage or recovery after pellet-freezing.