Evaluation of Changes in Milk Production and Quality in Dairy Cows with Mastitis Depending on Etiological Agents

Mastitis negatively impacts both milk production and milk quality. The aim of this study was to evaluate changes in milk production and composition in dairy cows with mastitis (n = 111) compared to controls (n = 111) and to assess the effect of a specific mastitis pathogen on selected milk quality indicators. The most common pathogen was Streptococcus uberis. Most mastitis cases were detected in summer (35%), in dairy cows in their fourth and higher lactations (52%), at 101–200 days of lactation (37%). A statistically significant difference (p <0.001) was found between control and mastitis cows in milk yield (32.3 vs 28.4 kg), lactose content (5.01 vs 4.72%), somatic cell count (4.84 vs 5.96 log), and fat-to-lactose ratio (0.83 vs 0.91). The somatic cell count in mastitis caused by Escherichia coli (3,270,000/ml) was significantly higher than in mastitis caused by other pathogens (p <0.001). The lactose content was also lowest in Escherichia coli mastitis compared to other mastitis cases (4.45%; p <0.001). It was found that the influence of specific pathogens on selected milk parameters varies considerably. The results obtained may provide a basis for optimizing preventive and therapeutic strategies in dairy cattle breeding.