Long-term preservation of chilled canine semen: Effect of commercial and laboratory prepared extenders

The present study was conducted to evaluate chilled semen conservation over time in 3 commercial and 4 laboratory prepared extenders, including a new Tris-glucose extender. The beneficial effect of adding egg yolk to these me dia was also analyzed. The effects of these extenders on motility and acros ome reaction were characterized objectively using a computer-aided semen an alyzer and the chlortetracycline staining, respectively. No significant dif ferences were observed when comparing the different commercial extenders wi thout egg yolk, but addition of egg yolk improved all motility parameters s ignificantly (preservation of 50% of motility was observed at 3.2+/-1, 2.9/-0.5, 2.3+/-0.5, 8.5+/-0.2, 5.4+/-1.1, 5.2+/-0.4 d, for Biladyl, green ext ender and fresh-phos extenders without and with egg yolk, respectively). Mo tility parameters were best preserved in egg yolk supplemented Biladyl exte nder with a mean percentage of 86.3+/-0.5 motile spermatozoa after 7 d at 4 degreesC. Efficacy of egg yolk-supplemented commercial extenders on sperm motility at 4 degreesC was (in decreasing order) as follows: Biladyl > gree n extender > fresh-phos. However, high quality motility and the percentage of motile spermatozoa wer e highest with some of the laboratory prepared extenders: a 50% conservatio n rate of motile spermatozoa was observed following the use of supplemented egg yolk extenders. These are classified in decreasing order as follows: T ris-glucose (13+/-1 d)> Tris-fructose (9.7+/-0.6) > EDTA (4. +/-0.6 d) > Tr is-bes (3.6+/-1.1 d). A low concentration of motile spermatozoa was still o bserved in the Tris-glucose egg yolk extender Lb d after collection, clearl y demonstrating the importance of the medium and the beneficial effect of e gg yolk on sperm motility of 4 degreesC chilled semen. Similar effects of e xtender were observed for acrosome reactions. Egg yolk clearly had a protec tive effect reducing acrosome reactions significantly in all media tested a s follows: the highest acrosome losses were observed in the fresh-phos and EDTA extenders without egg yolk; the lowest rate was observed with Tris-glu cose supplemented egg yolk extender. In conclusion, at 4 degreesC, egg yolk extender best-protected sperm motili ty parameters. Differences in osmolarity between the extenders in terms of substrate related to sperm metabolic activity may explain the optimal resul ts obtained using egg yolk-supplemented Tris-glucose extender, which preser ved motility and acrosome integrity in chilled dog semen. These results ind icated that good quality dog spermatozoa could be preserved for up to 10 d. (C) 2001 by Elsevier Science Inc.