Seasonal variations in the somatic cell count in cow's milk

Evaluating the somatic cell count (SCC) at the level of the herd or individual cows allows for efficient monitoring of mammary gland health. By analysing SCC, it is possible to identify subclinical cases of mastitis that do not manifest through visible clinical signs on the udder or changes in milk. This study was conducted on a modern dairy farm of the Holstein-Friesian breed in the municipality of Čapljina, Bosnia and Herzegovina. The total number of cows included in the study during 2022 and 2023 ranged between 325 and 335. Milk samples were preserved with azidiol and transported to the laboratory. Milk quality was assessed by determining the SCC in milk using the Fluoro-opto-electronic method, and by analysing the fat, protein, and lactose contents. The devices used in the study were CombiFoss 6200 – MilkoScan FT and Fossomatic FC 6000. A strong positive correlation was found between SCC and milk proteins, but not with milk fat. A significant negative correlation was found between SCC and lactose. There was no significant difference in the number of somatic cells by year, although there was a significant difference by season within the studied years. Winter stands out as the season with the lowest SCC, followed by spring and summer, while autumn had the highest count. Autumn also showed the largest oscillations in SCC, while spring had the smallest. Somatic cell counts over 200,000/mL were recorded from July to December 2022 and from May to November 2023. Zoohygiene conditions and milking hygiene measures should be additionally adjusted in summer and autumn to maintain the desired standards achieved in winter and spring.