Optical Somatic Cell Counting and Total Protein Analysis in a Dairy Herd Improvement Program ¹

Area of Science:

• Dairy Science
• Animal Science
• Food Science

Background:

• Accurate somatic cell counts (SCC) are vital for dairy herd management and milk quality assessment.
• Traditional milk sample preparation can be time-consuming and prone to errors.
• Understanding factors affecting SCC stability during storage and transport is essential.

Purpose of the Study:

• To simplify milk sample preparation for somatic cell counting.
• To evaluate the impact of preservatives and storage conditions on SCC.
• To explore correlations between SCC, milk protein fractions, and fat content.

Main Methods:

• Utilized a diluter for automated sample preparation (fixation, mixing, dilution).
• Assessed the effect of potassium dichromate preservative tablets on SCC.
• Investigated SCC changes under different storage temperatures and durations (20-23°C and 4-7°C).
• Conducted a large-scale survey of dairy herd improvement samples.
• Performed multiple correlation analyses with casein, noncasein protein, total protein, fat, and milk weight.

Main Results:

• Simplified sample preparation using a diluter proved effective.
• Potassium dichromate preservatives slightly increased mean SCC by 7,000 cells/ml.
• Somatic cell counts decreased significantly in samples stored beyond 2 days at room temperature or 4 days under refrigeration.
• A survey of over 52,000 samples showed 75% had SCC below 400,000 cells/ml.
• Strong correlations were found between total protein, SCC, and milk protein fractions.

Conclusions:

• A simplified, automated sample preparation method improves somatic cell counting efficiency.
• Proper sample handling, including timely testing and appropriate storage, is critical for accurate SCC.
• Testing for total protein and somatic cells can effectively estimate casein and noncasein protein levels.
• These findings are particularly valuable for optimizing cheese manufacturing processes.