The somatic cell count is one of the hygienic parameters of milk. According to current regulations it should not exceed the level of 400,000 per 1 ml of bulk tank milk. A higher level of this parameter puts in question the health status of the herd, especially as regards the so-called subclinical mastitis of the udder. According to Polskie Normy (PN, Polish Standards), the somatic cell count in milk should be established by the fluoro-opto-electronic method. The methodology of this procedure allows for preserving milk samples and examining them within 36 h after collecting. The research objective was to determine the effect of the preservative on the somatic cell count during milk storage. The research material consisted of raw milk from a farm with 8 Holstein-Friesian milk cows, aged 2–8 years. The sample was 2 l of milk obtained during milking 4 cows (0.5 l from each) in their 1^st or 2^nd lactations. The sample was divided into two equal parts, one of which was preserved with Bronopol (2-bromo-2nitropropan-1,3 diol; Milk-stoper) at the optimal dose of 0.002g/100ml (according to PN). The other half was used as a control. Throughout that period samples were stored at the temperature of 0-4°C. In total 50 milk samples were examined. The somatic cell count was determined by the fluoro-opto-electronic method with Fossomatic 5000, Foss Electric, in accordance with Polish standards PN-EN ISO 13366-3:2002 i PN-EN ISO 13366-2:2007. The somatic cell count in the milk ranged from 398,000 and 432,000/ml (the control and preserved samples 2 h after milking) to 395,000 and 434,000/ml (the control and preserved samples 36 h after milking). The analysis of the results suggests that the control and preserved samples differ in terms of the somatic cell count.

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