Canine Chilled Semen: Influence of Latex and Air

Introduction - Preservation of liquid semen at 5°C is an important technique in the breeding management of dogs. The aim of this kind of semen storage is to preserve gametes at low temperatures without reaching the freezing point. In fact, the longer the fertility potential of cooled semen can be extended, the easier it should be for breeders to time the insemination and transport the AI doses. But, oxidative damage to spermatozoa during storage is a potential cause of the decline in motility and fertility during hypothermic storage of liquid semen. The aim of this experiment was to evaluate the storage effect of canine chilled semen on syringes with and without latex and with and without air column.

Materials and methods - Ten healthy and sexually mature dogs between 2.5 and 8 years old and different breeds were used in this study, all of them have proven fertility. Two ejaculates were obtained with a 45min interval (4), from each dog by digital manipulation. Ejaculates were analyzed to determine its semen concentration, total number of spermatozoa, sperm motility and morphology, so that adequate semen quality was secured. Only ejaculates with total number of spermatozoa >400 x 107sptz, sperm motility >70% and < 30% of total pathology, were included in this study. Sperm concentration was determined using a Neubauer haemocytometer. Skim milk extender described by Kenney (8) was used to dilute the samples of semen to be chilled. This extender was prepared once and them it was frozen on -70°C and thawed before every trial.
After initial analyses, semen was extended up to 16mL, and than it was divided into four groups, 4mL each. They were storage in: syringes without latex, with (G1) and without (G2) air column; syringe with latex, with (G3) and without (G4) air column. Each group was divided into 4 aliquots, 1mL each. One aliquot of each group was warmed at 32°C for 10minutes after 6, 24, 48 and 72 hours of cooling, and than it was analyzed for sperm motility and vigor, as described by (5), plasma membrane integrity, as described by (2), acrossomal status as described by (8). Results were analyzed by ANOVA and tukey test and orthogonal contrast using Genes program. [...]