SOMATIC-CELLS IN THE MILK OF COWS WITH 100-DAY LACTATION

Variations of somatic cell counts in milk were investigated in a set of 142 cows with the first lactation, kept under the same conditions of housing and fooding, and not selected for milk performance; the cows were crossbreds of the Bohemian Pled breed with the Ayrshire and Holstein-Friesian cattle. The cell counts were determined in 10-day intervals of the 100-day part of lactation after calving, using the Fossmatic apparatus and prescribed methods. The results show (Tab. I, Fig. 1) that the somatic cell counts in the cow's milk are highest within 20 days after calving (544,000 per ml, and/or 533,000 per ml). A marked decrease beginning at this period was observed which relatively stabilized from the 31st day till the end of the period of investigation, that means the period of 100-day lactation, reaching the counts of 150,000 to 237,000 somatic cells per ml milk. Great variability of somatic call counts was found in the test set. The coefficient of variation showing the variability of the investigated values did not suggest any qualifiable trends. The value of the coefficient of variation fluctuated irreguarly from 117.9 to 324.9 %. In comparison with the data given by Schultz (1977), the inversion of the somatic cell counts to the lactation curve was demonstrated only with respect to the curve peak, that means to the ascendant stage of lactation. This can be seen in Fig. 2 showing the lactation curve peak for the period of days 47 to 55 after calving, and in Fig. 1 showing the relative stabilization of the decrease in somatic cell counts per 1 ml milk. The test set of cows demonstrated that the cows in the first lactation were able to produce milk with the somatic cell counts lower than 500,000 per ml from the 21st day after calving, and with the somatic cell counts lower than 300,000 per ml from the 31st day of lactation. This period is also convenient to investigate this milk quality parameter for the purposes of breeding work.