Anotace:
The purpose of the study was to asses the effect of calving season and dams’ parity on milk yield and gestation length of dairy cows. We examined 93 animals of Slovak spotted breed from the farm located in western Slovakia (Lower Váh region), in years 2014-2017. The herds’ average 305-d milk yield was 8133±1380 kg. The calving season was divided into four categories: spring (March to May), summer (June to August), autumn (September to November) and winter (December to February). The factor of dams parity was divided into 4 groups: 1st parity cows, 2nd-3rd parity cows, 4th and higher parity cows. Calving season affected significantly milk yield of dairy cows (P < 0.01). The highest 305-d milk production was oberved in winter calvings (8942±218 kg) and the lowest in spring calvings (7377±287 kg). The gestation length was not signifficantly altered by calving season (P > 0.32). Dams’ parity was not significantly affected by 305-d milk yield (P > 0.22). Nevertheless, the animals on the 4th and higher lactation were numerically more productive (8481±259 kg) compared to the dairy cows on their 1st,2nd-3rd lactation (8123±264 kg; 7884±223 kg; resp.). The dams’ parity significantly affected gestation length (P < 0.02), with the shortest gestation length in 1st parity dams (278±2 days) and the longest gestation in 2nd-3rd parity dams (284±1 days).To sum up, our results suggest significant role of calving season in relation to milk yield and significant effect of dams’ parity on gestation length.