Handling milking as a risk factor in the occurrence of microorganisms in raw milk

Abstract

Milk is naturally a good provider of a whole range of nutrients, however an inadequate milking may significantly interfere on its nutritional and microbiological quality. The main purpose of this study was to isolate and identify microorganisms from bulk tanks of southern Rio Grande do Sul state, Brazil and establish a correlation between animal management and presence of pathogens in the milk. To this end, raw milk samples were collected from different dairy herds and submitted to microbiological analyses. Mean bacterial counts were Staphylococcus sp. (5,32x106 CFU/mL), S. aureus (1,33x105 CFU/mL) and enterobacteria (1,82x107 CFU/mL). The major pathogens isolated and their respective frequency were Escherichia coli (27.8%), Streptococcus agalactiae (6.2%), S. dysgalactiae (37.2%), S. uberis (16.8%), Candida sp. (15.7%), Aspergillus sp. (5.8%), Trichosporum sp. (3.6%) and Cryptococcus sp. (1.5%). In addition, it was identified an Odds Ratio of 3.2 for S. agalactiae regarding manual milking and 3.1 when a single cloth towel was used for drying the udder. For S. bovis the Odds Ratio was 2.8 in properties milking their animals in stalls wood. Somatic cell count (SCC) was significantly higher (p=0,003) in milk samples manually extracted in comparison with machine milking. Likewise, manual milking resulted in the increase in S. aureus counts (p=0.04). Pre-dipping practice have contributed for a significant reduction (p=0.04) in the Staphylococcus sp. counts. Taken together, our results show that the adoption of poor management practices can negatively interfere in the microbiological quality of milk increasing the risks of occurrence of pathogens and their counts.