Changes in the Production and Composition of Cow's Milk in Response to an Increase in Somatic Cells

A study was carried out in five herds from central and southern Chile in order to establish the effect of increasing somatic cell counts on the production and composition of milk. Information coming from a monthly control system for each of the animals belonging to the experimental dairy herds was managed in a computer database designed for said purpose. Starting from the records registered in two years of data collection, the relations existing among the somatic cell count and the production and composition of milk were studied. A general adjustment model was established allowing an adequate explanation of this phenomenon (y = a + bx + cx2 +, where a, b, and c are parameters; y = Total Solids, % (ST); Butterfat, % (MG) and Non Fat Solids, % (SNG); and x = level of mastitis (assessed in ranges 0 to 9)). The main results were the following: a one unit increment in somatic cell count represented a decrease in milk production of 0.760 and 0.790 kg d-1, for range 1 vs. 0.530 and 0.810 (P