The goal of this study was to evaluate somatic cell count (SCC) in bulk tank milk samples in the milk delivered to the industry by dairy farmers; also, to allot of the bulk tank milk samples in somatic cell score (SCS) class. Bulk tank milk samples are routinely analyzed at the central laboratory of the Programa de Análise de Rebanhos Leiteiros do Paraná (PARLPR) of the Holstein Association, state of Paraná, Brazil. The present study was on a data set of the PARLPR containing 257,540 bulk tank milk samples from 32,590 herds delivering milk to 18 dairy industries in the states of Santa Catarina, Paraná and São Paulo, analyzed between January 1999 and November 2001. General Linear Models procedures were used to study the effects of micro region, year and month of the test, herd and age of the sample on SCC in bulk tank milk samples. Mean and standard deviation for SCC samples in bulk tank milk samples were 486,812 and 401,547 cells/mL, respectively. All factors had a highly significant effect on the SCC. Micro regions were highly variable on the SCC, from 602,000 to 242,000 cells/mL. The highest means were observed in 2001 (483,000 cells/mL). Highest SCC means were observed in January (497,000 cells/mL) and lowest in September (442,000 cells/mL). The effect of age of the sample showed reduction in SCC levels until day four; after day seven samples were highly variable. Sixty-four percent of all samples showed a SCS of five or more.
bulk tank milk; milk quality; SCC; somatic cell score
