Effects of seminal plasma and three extenders on canine semen stored at 4 degrees C

Semen preservation and artificial insemination (AI) in the canine has become a common practice in veterinary medicine. Chilled dog semen is easy to handle, and several extenders can be used. The aim of this study was to compare the effects on canine spermatozoa of seminal plasma and 3 extenders commonly used for chilled semen preservation in clinical practice. The characteristics evaluated were sperm motility; velocity; plasma membrane status (assessed with a fluorescence staining technique and hypo-osmotic swelling test); acrosome morphology; semen pH; and semen osmolarity. These criteria were monitored daily in the ejaculates of 11 dogs. The ejaculates were divided into 4 aliquots. Each aliquot was extended in autologous seminal plasma, egg-yolk Tris, egg-yolk milk or egg-yolk cream and preserved at 4 degrees C for 4 d. In 10 of 11 semen samples extended in autologous seminal plasma, motility had already decreased to 0% by Day 2, and the percentage of spermatozoa with intact membranes was lower than in the 3 extenders (P < 0.05). Motility up to Day 4 was higher in egg-yolk Tris-stored spermatozoa (53.6%) than in those preserved in egg-yolk milk (30.4%) and egg-yolk cream (14.1%). Spermatozoa stored in egg-yolk Tris also had the highest sperm velocity, whereas no difference was found in plasma membrane or acrosome status (P>0.05). Egg-yolk Tris extender seems to be superior to the other extenders tested, to preserve dog semen at 4 degrees C, although differences were not significant for all the parameters.