The influence of seminal plasma removal by cushion centrifugation and filtration on characteristics of dog semen

The routine removal of seminal plasma during processing of canine semen remains controversial. This study compared standard centrifugation (750 × g , 5 min, 22 °C), cushion centrifugation (1000 × g , 20 min, 22 °C), and syringe-filter filtration (Millex-GP 0.22 μm, retrograde flushing with 1 mL TRIS–citric acid–fructose buffer) for their effects on canine semen quality. Sperm concentration, sperm recovery rate, total motility, progressive motility, membrane integrity, morphology and kinematics were evaluated. All semen processing methods resulted in a considerable sperm loss with sperm recovery rate being less reduced after standard centrifugation relative to cushion centrifugation and filtration (Standard 80.0 ± 3.1 a ; Cushion 55.1 ± 3.1 b ; Filter 59.8 ± 4.1 b %; ab: p < 0.001). Sperm concentration was considerably reduced after cushion centrifugation and filtration (Control 409.4 ± 27.9 a ; Standard 738.6 ± 69.1 ac ; Cushion 275.4 ± 29.8 ad ; Filter 229.0 ± 34.8 b x 10 6 /ml; ab, cd: p < 0.01). Total and progressive motility were significantly decreased after filtration vs. both centrifugation methods. Membrane integrity was most reduced in filtered semen, standard centrifugation caused a numerically minor but significant decrease in membrane integrity vs. control and cushion centrifugation. Filtration decreased kinematic parameters in comparison to standard and cushion centrifugation. Filtration significantly increased the percentage of morphologically abnormal sperm that did not differ among control, standard centrifugation and cushion centrifugation. In conclusion, processing methods investigated in this study decreased semen characteristics compared to raw semen of healthy dogs. Effects of filtration clearly exclude the here tested method from further use and investigations in dogs. Cushion centrifugation offered limited benefits, but without improvement of sperm recovery by modifications of the method it is not of interest in commercial dog semen freezing.