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The objective of this study was to investigate the variation in milk yield and milk flow traits and to analyse the main factors influencing the milkability of ewes. Milk yield and milk flow traits were: milk yield to 10 s, milk yield to 30 s, milk yield to 60 s, machine milk yield, stripping yield, total milk yield, percentage milk yield to 30 s, percentage milk yield to 60 s, stripping percentage, machine milking time and average milk flow. Primiparous and multiparous Improved Valachian, Tsigai and Lacaune purebred and crossbred ewes were considered. Crossbred ewes were crosses of Improved Valachian or Tsigai ewes with Lacaune (genetic portion of Lacaune was 25, 50 and 75 %, respectively). A total of 359 to 370 ewes were measured depending on trait. Mixed model with fixed and random effects using the REML (restricted maximum likelihood) method was applied. All traits were significantly (P<0.01) influenced by genotype and year. Some traits were significantly (P<0.05 or P<0.01) influenced by parity, stage of lactation and interactions considered between genotype and parity and between genotype and stage of lactation. The repeatability varied from 0.23 to 0.43. Regardless of breed, mean values of machine milk yield, total milk yield and of stripping percentage were 318.3 ml, 436.6 ml and 27.7 %, respectively. Stripping percentage varied extensively, from 0 % to 95 %. The highest stripping percentage (37.8 %), the highest total milk yield (523.1 ml) and the second highest machine milk yield (330.3 ml) were found in Lacaune purebred ewes. The crossbred ewes were better than Improved Valachian and Tsigai purebred ewes in all examined traits, except for milk yield to 10 s, percentage milk yield to 30 s, percentage milk yield to 60 s, stripping percentage and machine milking time. Obtained results suggest that crossbreeding of local dairy breeds with Lacaune may be a good strategy for improvement of milkability of dairy sheep population in Slovakia.