The Relationship of Somatic Cell Count with Milk Yield and Composition in Different Stages of Lactation in Holstein Cows [Odnos broja somatskih stanica te prinosa i sastava mlijeka u različitim stadijima laktacije u holštajnskih krava]

Abstract

Globally, the milk yield of Holstein cows has increased considerably, but this situation has reduced the cows’ tolerance to environmental factors and, thus, it has negatively affected udder health and milk quality. This study aimed to determine the influence of somatic cell count (SCC) on milk yield and its composition in early (<100 days), mid (100–200 days), and late lactation (>200 days) between November 2019 and August 2020. The study material consists of 927 records of 132 Holstein cows raised on a commercial dairy cattle farm in the Kırşehir province of Turkey. SCC was categorized into three groups (<100x103 cell/mL, 100-200x103 cell/mL, and >200x103 cell/mL). SCC data were logarithmically transformed to log10 base. In the study, logSCC, test day milk yield (MY), fat content (FC), solidsnot-fat (SNF), protein content (PC), lactose content (LC), fat yield (FY), and protein yield (PY) were recorded as 5.12±0.01, 37.54±0.34 kg, 3.59±0.02%, 9.08±0.01%, 3.35±0.01%, 4.99±0.01%, 1.33±0.01 kg, and 1.26±0.01 kg, respectively. LogSCC, MY, FC, SNF, PC, LC, FY, and PY were significantly affected by the parity, lactation stage, and sampling season (P<0.05). Both milk yield and its composition in late lactation were negatively affected by high SCC compared to early and mid-lactation. MY, SNF, PC, LC, FY, and PY were determined to be the highest in cows with SCC<100x103 cells/mL, and the lowest in cows with SCC>200x103 cells/mL. Consequently, it may be that milk loss related to an increase in SCC was, consequently, highest toward the end of lactation. As a result, we suggest that prevalence measures should focus on reducing the incidence of SCC toward the end of lactation in Holstein cows.