Contamination of cow's raw milk by psychrotrophic and mesophilic microflora in relation to selected factors

The objective of the paper was to analyse the influence of dairy cow management technology, milking method, predipping and summer grazing on the contamination of cow's raw milk by mesophilic (TBC), psychrotrophic (PBC), lipolytic (PLiBC) and proteolytic (PPrBC) bacteria. The values of TBC, PBC, PLiBC and PPrBC in bulk milk samples were determined by the culture method according to IDF standards. Investigations were carried out in nine stables of seven dairy farms from January 2005 to June 2006. Summer grazing has the most marked influence on the values of studied parameters. Farms with summer grazing had a lower microbial contamination of milk compared to farms without grazing and the difference was statistically highly significant in all studied parameters (P < 0.001). A positive effect of predipping on a reduction in the values of milk microbial contamination was proved while the difference between farms with predipping and those without it was on a significance level P < 0.05 to 0.001 except PUBC. A comparison of the influence of dairy cow management technology indicated the lowest values of all microbiological indicators in loose cubicle littered housing, higher values were determined in stanchion littered housing and the highest in loose slatted-floor housing. A statistical difference between the technologies was proved mainly in TBC (P < 0.001). Farms with milking in milking parlours had a lower microbial contamination of milk compared to farms that used the in-stall milking pipeline system but the difference was statistically significant only in TBC (P < 0.05).