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Factors influencing somatic cell count and leukocyte composition in cow milk: A field study
S Mondini1, G Gislon1, M Zucali1
1Department of Agricultural and Environmental Sciences, University of Milan, Milan, Italy 20133.
Insights
Somatic cell count (SCC) in cow milk is influenced by lactation stage and parity. Neutrophils (NEU) and lymphocytes (LYM) increase, while macrophages (MAC) decrease, particularly at lactation
Area of Science:
- Dairy science
- Veterinary immunology
- Animal health
Background:
- Somatic cell count (SCC) in cow milk is a key indicator of udder health and milk quality.
- Milk SCC is composed of various leukocytes, including neutrophils (NEU), lymphocytes (LYM), and macrophages (MAC), which play critical roles in the immune response to mastitis.
- Understanding factors influencing SCC and its leukocyte composition is crucial for managing bovine mastitis.
Purpose of the Study:
- To investigate the influence of lactation stage, parity, and milk electrical conductivity on SCC and leukocyte composition (NEU, LYM, MAC) in dairy cows.
- To identify risk factors associated with high SCC levels and altered leukocyte profiles.
- To correlate milk SCC and leukocyte dynamics with critical periods of udder health throughout lactation.
Main Methods:
- Data collected from 179 dairy cows across 6 farms throughout their entire lactation period.
- Statistical analyses including mixed models and logistic regression were used to examine relationships between variables.
- Factors analyzed included lactation stage, parity, milk electrical conductivity, milk production, and hygiene scores.
Main Results:
- Parity and lactation stage significantly affected milk SCC and leukocyte composition.
- Highest milk NEU and lowest MAC percentages were observed at the beginning and end of lactation.
- High milk electrical conductivity, low milk production, parity number, and poor hygiene were linked to increased SCC.
- Elevated NEU and LYM percentages were associated with a higher risk of elevated SCC.
Conclusions:
- Lactation stage and parity are critical determinants of milk SCC and leukocyte profiles in dairy cows.
- The early and late stages of lactation represent heightened periods of risk for udder health, characterized by specific leukocyte shifts.
- Factors like milk conductivity, production levels, and hygiene management significantly impact SCC and warrant attention for mastitis prevention.
Abstract:
In recent years, a proliferation of studies investigating the composition of milk SCC, focusing on neutrophils (NEU), lymphocytes (LYM), and macrophages (MAC) has occurred. These 3 components are indeed crucial for the animal's immune response to mastitis-causing pathogens. The study examined various factors influencing SCC and leukocyte components in cow milk, including lactation stage, parity, and milk electrical conductivity, using data from 179 dairy cows across 6 farms throughout the entire lactation. Statistical analyses, including mixed models and logistic regression, were employed to investigate the relationships between these variables and identify risk factors for high SCC levels. Results showed that factors such as parity and lactation stage were significantly associated with somatic cell composition. In particular, the highest milk NEU values (>60% of the total leucocytic fraction) and lowest MAC values (<20%) were found at the beginning and end of lactation, which are the critical periods for udder health. High milk electrical conductivity, low milk production, parity number, and poor hygiene scores were identified as contributing to increased SCC. Additionally, elevated percentages of NEU and LYM in milk were associated with increased risk of high SCC values, indicating potential udder health issues.
