Comparison between different dilution rates on canine semen freezing using Tris-buffer with the addition of egg-yolk and glycerol [Comparação entre diferentes diluições na congelação do sêmen canino utilizando o tampão tris acrescido de gema de ovo e glicerol]

Standardized sperm concentration and volume:volume extension were compared as dilution rates for canine semen freezing. Six proven stud dogs were submitted to two seminal collections by manual stimulation. Semen was evaluated and extended in tris plus egg-yolk and glycerol according to two different dilution rates. The first one was based on a standardized sperm concentration of 200x10 spermatozoa/ml and the second was a volume:volume extension at a proportion of one part semen to one part extender. Semen was frozen, stored in liquid nitrogen and thawed after one week. Sperm motility and vigor were appraised after each stage of the process and at 15 and 30min post-thawing. Sperm morphology was analyzed after collection and thawing. No differences were observed between treatments after thawing regarding sperm motility and vigor, normal sperm morphology rate or longevity. Both dilution rates can be efficiently used for canine semen freezing.