Cows with High SCC Exhibit Poorer Performance and Milk Quality, Regardless of the Season

This study aimed to examine the relationship between a high somatic cell count (SCC) in cows and milk quality during the hot season in different breeds. Milk samples from 500 cows in the hot season and 431 in the cold season of 2022 were collected across 39 farms in Santa Catarina, Brazil. The samples were analyzed for SCC, milk composition, and physical attributes. Cows were also evaluated for udder depth, udder clearance, teat-end condition, and leg and udder cleanliness. Based on the SCC levels, cows were categorized as low (≤200,000 cells/mL), medium (>200,000 and ≤615,000), or high (>615,000). Data were analyzed by ANOVA with a statistical model that included the effects of the SCC class, season, days in milk, parity, genetic group, and the interaction of the SCC level and season. The results showed that cows with a high SCC produced less milk with lower component levels but higher chloride content. Milk from the hot season had lower acidity and reduced component levels. The impact of SCC on the physical traits of milk did not vary with season. Furthermore, cows with deeper udders and lower udder clearance were more likely to have a high SCC, regardless of genetics. Both a high SCC and hot temperatures independently compromised milk yield and quality, thereby increasing the risk of culling. Therefore, improving udder conformation and avoiding cows with deep udders may help to reduce SCC levels.