To analyze fluctuation of indexes of consist and quality of milk of black and white and red-spotted cows during different months and seasons of lactation. The work was performed in Lithuanian Academy of Veterinary, department of stockbreeding as well as public enterprise Pieno Tyrimai during Master studies 2005-2007. During the analysis, data of controlled cows’ productivity was analyzed according to accounting information of cattle breeding. During the analysis we evaluated 98 Lithuanian black and white cows, Lithuanian red-spotted cows, as well as Ayrshire cows. Milk yield of Lithuanian black and white cows was 1160 kg of milk more than Ayrshire and 252 kg of milk more than Lithuanian red-spotted. Average milk yield of Ayrshire cows was 92 kg more than Lithuanian red-spotted. There was 0.53–0.83% of fat in milk of Lithuanian black and white cows, protein was 0.24–0.25% less than in Ayrshire or Lithuanian red-spotted. Lithuanian black and white cows had 1.0–15.0 kg of milk fat (or 0.3 –4.8%), milk protein – 23.0–25.0 kg (or 11.2–9.4%) more than in Ayrshire or Lithuanian red-spotted. During all periods of lactation most milk fat were found in milk of Ayrshire cows (5.05%), least in Lithuanian black and white cows (4.21%). Milk fat of Lithuanian black and white and Lithuanian red-spotted was less in comparison with Ayrshire cows. During all months of lactation most amount of protein was found in Lithuanian red-spotted and Ayrshire (3.69-3.68%), and least – in Lithuanian black... [to full text]