The effects of season and lactation number on the composition of holstein cattle raw milk

This study aimed to determine the somatic cell count (SCC) in milk from Holstein Friesian cows and to examine the variation of SCC based on season and lactation order, as well as its effects on milk quality. The research was conducted at a private dairy cattle farm in Diyarbakır province between March 2023 and March 2024, with a total of 210 milk samples collected over four seasons (spring, summer, autumn, winter) in quarterly periods. Somatic cell count was measured using the Somatos Mini device, while dry matter, protein, fat, and lactose contents were determined using the Milkotester Master Classic device. The effects of lactation order and season were analyzed using the Least Squares Method, with multiple comparisons conducted using Duncan's test.The average fat, protein, dry matter, lactose, and SCC contents of raw milk samples throughout the year were determined to be 3.61%, 3.22%, 12.71%, 4.68%, and 211.70 cells/ml, respectively. The study found statistically significant differences between lactation orders in terms of fat, dry matter, protein, and SCC contents, while no significant differences were observed in lactose content. Significant and positive correlations were detected between lactation order and both dry matter (r = 0.383, p < 0.001) and SCC (r = 0.355, p < 0.001), indicating that as lactation progresses, dry matter and SCC levels increase. There were negative correlations observed between season and both milk fat (r = -0.333, p < 0.001) and SCC (r = -0.333, p < 0.001), suggesting that environmental factors, especially heat stress during the warmer months, can cause changes in milk composition. During these periods, fat content decreased while SCC increased, which could contribute to a decline in udder health. A negative correlation was also found between season and dry matter (r = -0.278, p < 0.001).In terms of the relationships between milk components, a significant positive correlation was found between protein and lactose (r = 0.277, p < 0.001), suggesting that these components tend to increase together. However, no significant correlations were observed between fat and other components.In conclusion, the study's findings indicate that lactation order and season have significant effects on milk composition and somatic cell count.