SUBJECTING CANINE SEMEN TO THE HYPOOSMOTIC TEST

The hypo-osmotic swelling test (HOS-test) was evaluated in 8 postpubertal dogs, ranging in age from 10 months to 3 years, to determine the response of canine spermatozoa to the HOS-test and the association between the sperm response to the test and semen parameters as well as to assess the effects of heating and storing semen on the response of the spermatozoa to the HOS-test. As in the human and bovine species, the canine spermatozoa curled ('swelled') under hypo-osmotic conditions. due to influx of water and expansion of the sperm membrane. Both fructose and sodium citrate solutions induced easily identifiable curling of spermatozoa, but with significant variations in sperm response to the 2 solutions. A maximal number of curled spermatozoa was observed in 60 mosmol fructose, at 45 minutes of incubation. Using the 60 mosmol fructose solution, a high correlation (r=0.94 P<0.0001) was observed between the percentage of curled spermatozoa and sperm motility. This is not surprising since sperm motility is partly dependent on membrane transport (membrane integrity). Comparatively, the correlations between curling and midpiece abnormality (r=0.22 P>0.32), and between curling and tail abnormality (4=0.38 P>0.08) were low. Storage of semen adversely influenced the sperm response to the HOS-test. The results of this study indicate the possible predictive value of the HOS-test in selecting individual ejaculates from stored canine semen samples for insemination. In conclusion, the HOS-test may be a useful addition to standard semen analysis for the identification of males that may be subfertile despite a normal spermiogram. Further evaluation of the test is needed to assess its diagnostic significance in this species.