Objective: This study was focused on the influence of the skimmed milk-based extender (SM), the INRA 96 extender and BotuSemen Gold extender on parameters of stallions' ejaculate during storage.Methods: In this study, 14 stallions between 4 and 20 years of age were monitored. Total andTotal and pProgressive motility, viability and morphology of sperm were evaluated at time intervals of 24, 48 and 72 hours after collection. Results:The total and progressive motility was significantly higher in the INRA 96 and BotuSemen Gold extenders than in the skimmed milk-based extender at all time intervals (p < 0.05). After 48 and 72 hours, the INRA 96 preserved the viability of the semen better than the SM (p < 0.01). After 72 hours, the share of viable spermatozoa in the INRA 96 samples was 59.16 ± 1.06% and in the BotuSemen Gold samples, 55.00 ± 1.20% (p < 0.05) The total motility, progressive motility and values of sperm with normal morphology were significantly higher in the INRA 96 and BotuSemen Gold extenders than in the skimmed milk-based extender (p < 0.01). The sperm viability differed significantly in all extenders (p < 0.01). The highest value of sperm viability was in INRA 96 (64.69 ± 0.67%) and lowest in skimmed milk-based extender (59.70 ± 0.81%). The highest differences occurred at 72 hours of storage. The highest differences occurred at 72 hours of storage.Values of total motility, progressive motility and sperm viability decreased over time (p < 0.01). In case of sperm morphology there was no statistically significant decrease between 48-and 72-hour time intervals. Conclusion:It can be concluded that the extenders with a chemically defined composition have shown better indicators of insemination capabilities in ejaculates than the skimmed milkbased extender. The BotuSemen Gold extender is a suitable alternative to the INRA 96, when

The aim of this study was to compare two methods for determining the concentration of sperm in stallion ejaculate and to evaluate the influence of different levels of concentration on the determination of sperm motility using an objective method. The total number of evaluated samples was 123. For the experiment, 14 stallions of different breeds housed in the Tlumačov Provincial Stud Farm were used. Sperm concentration was assessed by the hemocytometric method using a Bürker chamber and the automatic method using the Sperm Class Analyzer®. The SCA system was used to evaluate sperm motility. The samples were divided into 6 groups with sperm concentrations of 50, 100, 150, 200, 250 and 300•10 6 sperm ml -1 . The results were statistically evaluated by Tukey's HSD test. There were statistically significant differences in the determination of sperm concentrations between the hemocytometric method and the SCA system in samples with concentration exceeding 100•10 6 sperm ml -1 . Sperm motility increased in samples with higher concentration, however the effect of sperm concentration on motility parameters has not been statistically significant. The results of this study indicate that samples with sperm concentration higher than 100•10 6 sperm ml -1 reduce the accuracy of the SCA system evaluation and these samples need to be diluted to concentration ≤100•10 6 sperm ml -1 for more accurate evaluation.