Do milking practices influence the bacterial diversity of raw milk?

The link between milk production practices and bacterial diversity of 67 raw milks from dairy farms in the Savoie and Haute-Savoie regions of France was studied by Single Strand Conformation Polymorphism (SSCP) analysis. The milking practices and the cleanliness of different parts of the cow housing were evaluated. The SSCP bacterial profiles allow to classify the 67 milks into three groups: group A was characterised by a majority of Gram-positive non-lactic acid bacteria (Corynebacterineae and Micrococcaceae) and a high level of hygiene in milking practices. The SSCP profiles of groups B and C were close but different from those of group A: they were both dominated by lactic acid bacteria and by a less intensive hygiene practices. The group B milks were characterised by the dominance of Gram-negative bacteria and Lactococcus lactis species while those of group C were dominated by Brevibacterium linens and Leuconostoc mesenteroides. The variation of balance between bacterial populations can be associated with differences in hygienic milking production practices.