This study evaluated the variation of quality of bulk tank milk using 2,970 samples, collected from October 2005 to September 2006. Milk composition analyses, somatic cell count (SCC), and total bacterial count were performed. Climate conditions were evaluated by temperature and relative air humidity collected at meteorological stations throughout São Paulo state. Autumn season was related to the highest values for protein and fat, 3.65 and 3.21%, respectively. For somatic cell count, it was observed an increase in the count in the summer and for bacterial count in the spring. The influence of season on milk price was observed for dairy producers in a program, with maximum bonus of 7.9% in the autumn. One of the most important parameters related to penalty for lower quality of milk was SCC, since it can affect the quality of some dairies by the alteration of casein/whey protein proportion. Therefore, the effects of SCC and season should be considered into the process of formulation of tables for milk payment program.
dairy industry; climatic effects; milk price
