Impact of farm- and cow-related factors on milk coagulation properties in Estonian Native and Estonian Red breeds

Abstract This study evaluated the relative importance of farm- and cow-related factors affecting milk coagulation properties in commercial and native cattle breeds exposed to different housing and management systems. The study included 86 Estonian Red (ER) and 132 Estonian Native (EN) cows from 12 single-breed and 3 dual-breed dairy farms; farm characteristics and management practices were assessed through on-site visits and manager interviews. Individual milk samples were collected every second month during the morning test-day milking from November 2020 to January 2022 and analysed for composition, coagulation properties, casein micelle size distribution, fat globule size distribution and κ-CN genetic variants. The results showed no significant differences in milk coagulation properties between the two breeds. Among cow-related factors, curd firmness in both breeds was most strongly associated with milk protein content (ER: r = 0.23; EN: r = 0.19), casein content (ER: r = 0.30; EN: r = 0.27) and the casein-to-protein ratio (ER: r = 0.17; EN: r = 0.28). The κ-casein genotype affected both the rennet coagulation time and curd firmness in both breeds. The genetic effect of the sire was greater in the ER breed. Separate breed-specific models showed that the proportion of variance in milk coagulation traits explained by farm effects was approximately three to four times higher in EN cows compared to ER cows. These findings suggest that strategies for improving milk coagulation should be tailored to the production context.