Single-layer centrifugation through colloid selects improved quality of epididymal cat sperm

Abstract 

The objectives were to determine the: 1) extent of epithelial and red blood cell contamination in epididymal cat sperm samples recovered by the cutting method; 2) efficacy of simple washing, single-layer centrifugation (SLC), and swim-up for selecting epididymal cat sperm; and 3) effects of freezing and thawing on cat sperm selected by various techniques. Ten unit samples were studied; each contained sperm from the cauda epididymides of four cats (total, ∼200×10⁶ sperm) and was equally allocated into four treatments: 1) simple washing, 2) single-layer centrifugation through colloid prior to cryopreservation (SLC-PC), 3) single-layer centrifugation through colloid after cryopreservation (SLC-AC), and 4) swim-up. Centrifugation (300×g for 20min) was done for all methods. The SLC-PC had a better recovery rate than the SLC-AC and swim-up methods (mean±SD of 16.4±8.7, 10.7±8.9, and 2.3±1.7%, respectively; P<0.05). The SLC-PC, SLC-AC and swim-up samples contained less red blood cell contamination than simple washed samples (0.02±0.01, 0.02±0.04, 0.03±0.04, and 0.44±0.22×10⁶cells/mL, respectively; P<0.05). Although the proportion of sperm with head abnormalities did not differ among selection methods (P>0.05), SLC-PC yielded the highest percentage of sperm with normal midpieces and tails (P<0.05), due to the lowest proportion of coiled tails (P<0.05). Furthermore, the SLC-PC was as effective as swim-up in removing sperm with proximal droplets, and selecting motile sperm, as well as those with intact membranes and DNA (P>0.05). In conclusion, both SLC-PC and swim-up improved the quality of epididymal cat sperm, including better morphology, membrane and DNA integrity, and removal of cellular contamination. However, SLC had a better sperm recovery rate than swim-up.

Keywords: Colloid, Sperm separation, Semen, Sperm morphology, Feline