A retrospective study of the relationship between canine age, semen quality, chilled semen transit time and season and whelping rate and litter size

The objectives of this study were to investigate the effect of the dog's age. semen quality, and the duration and season of semen transit on whelping rate and litter size after insemination with transported chilled extended semen. The sperm rich fraction was collected from 43 dogs of 18 breeds, which were presented at the Clinic for chilled semen transport, in the period from 2017 to 2021. Immediately after collection, the total sperm concentration and count, motility, membrane integrity (HOS test), the percentage of live spermatozoa and sperm morphology (eosin nigrosin staining) were evaluated. The sperm rich fraction was centrifuged and diluted with Tris - fructose - citrate extender with the addition of 20% (v/v) egg yolk, then chilled and prepared for shipping. A dose consisted of at least 200x10(6) live. motile, morphologically normal spermatozoa. The data on the dog's age, chilled sperm transit time, the season of transit, and the whelping rate and litter size after insemination were recorded. The whelping rate was 55.8% with a mean (+/- SEM) litter size of 4.71 +/- 0.58 pups. The total number of spermatozoa was higher in artificial insemination (AI) that resulted in whelping compared to unsuccessful AI (P<0.05). No difference was observed for any of other sperm quality parameters tested, such as the dog's age or season of transit regarding whelping rate or litter size. Transit time significantly affected the whelping rate (P<0.01), at (mean +/- SEM) 21.50 +/- 1.28 and 37.00 +/- 5.59 h in successful and unsuccessful AI, respectively. In conclusion, analysis of the factors related to the dogs identified total sperm count and transit time as factors that significantly affected whelping rates in bitches inseminated with transported chilled extended semen.