Effect of some environmental factors on the number of somatic cells in the milk of Black and white cows | Влияние на някои средови фактори върху броя на соматичните клетки в млякото при крави от Черношарената порода

The aim of this study was to establish the influence of some environmental factors - farm, season of calving, month of controlling, consecutive lactation and lactation period on the somatic cells count in the milk of black and white cows. The study was conducted in three cattle farms with different technologies for rearing of dairy cows - C, M and T. The study included only lactating cows during the study. Data on milk yield, milk composition and somatic cells are taken from official herds control. Data are for lactations occurred in the period from 31.08.2012 to 01.01.2011. A total of 193 lactations from I-st to VII-th, and for assessing the impact of various factors do 1,891 controls. The study included only lactations with a length of not less than 240 days, and the data for the longer were taken by to 305th day. The number of somatic cells was lowest for the cows rearing in free stalls, Farm T - 270,44 x103/ml. In cows on both tied farms somatic cells count is significantly higher, respectively Farm T - 787,69 x103/ml and farm M 622.01 x103/ml. Season of calving has a statistically significant effect on somatic cells count as the highest number is reported for cows calved in the summer - 521.99 x103/ml, followed by those calved in the winter - 413.29 x103/ml. The cows calving in autumn have the lowest number of somatic cells - 330.84 x103/ml. Calendar month does not have a statistically significant impact on the somatic cells number in milk, but was reported the highest number in August - 610.9 x103/ml and slightly lower over 400x103/ml, but relatively high during the winter months. Somatic cells count is influenced by another reliable lactation. The lowest number was observed for the cows on the first lactation – 251.54 x103/ml, and the highest for the cows on IV-th and more lactations – 633.22 x103/ml. The period of lactation there was no statistically significant effect on the somatic cells count, but a trend to increase the number after the second month of lactation was observed.