Somatic Cell Level in Dairy Cows’ Milk During Extended Lactation / Poziom Komórek Somatycznych W Mleku Krów W Laktacji Przedłużonej

Milk analysis was performed in Black-and-White cows with a different percentage of Holstein- Friesian (HF) genes, which calved in 1995-2008 and were included in the milk recording programme. The aim of the present study was to determine the somatic cell level in milk obtained during the extended lactation phase (from day 306 to the end of lactation) compared to the standard lactation. The average somatic cell count in the milk of cows in extended lactation was 409,000 in the standard lactation of 305 days, 542,000 in the extended lactation phase and 427,000 per mL in full lactation of 381 days. Somatic cell count in the milk produced during the extended lactation phase (from day 306 to the end of lactation) was significantly higher compared with the milk harvested during the 305-day lactation. The lowest average somatic cell score (SCS) per mL raw milk in the extension phase was determined in the milk of primiparous cows (3.83). The factors which significantly affected the somatic cell count in the milk of cows extending their standard lactation included parity (lactation) and average daily milk yields from day 306 until the end of lactation. The correlation coefficients calculated for the somatic cell score (SCS) in standard lactation and in extended lactation phase, within selected factors, indicate that there was a positive correlation for both the lactation groups (standard lactation and extension period) as well as lactation (parity) (rp = 0.23 and rp = 0.33; P<0.01). It was also demonstrated that somatic cell count was on the decrease with increasing daily milk performance during extended lactation (rp = -0.23; P<0.01).