Importance of on-farm management practices on lactate-fermenting Clostridium spp. spore contamination of Manchega ewe milk: Determination of risk factors and characterization of Clostridium population

This work studies the on-farm management practices that increase the risk of developing high lactate-fermenting Clostridium spp. spore counts in ewe milk. Moreover the ecology of the Clostridium population was studied in relation to those management practices. A total of 136 bulk tank milk samples belonging to 23 Manchega ewe flocks were analysed for lactate-fermenting Clostridium spores by the most probable number technique. Information about the housing conditions, the feeding characteristics and the milking parlour hygiene were also collected from the 23 flocks. A logistic regression analysis indicated the farm-made total mixed ration, the wet brewers' grains used for feeding, and the presence of dust in the milking parlour as the on-farm management risk factors that lead to an increase of Clostridium spp. spore counts. A total of 114 Clostridium isolates from milk samples were typed using randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). The 35 different genotypes obtained were subsequently identified by restriction analysis of 16S-rRNA gene (16S-ARDRA), so three populations were observed: 93.86%, 3.51% and 2.63% corresponding to Clostridium sporogenes, Clostridium beijerinkii and Clostridium tyrobutyricum respectively. The risk factors of high Clostridium spp. spore counts also increased Clostridium population diversity and favoured the presence of C. beijerinkii and C. tyrobutyricum. Moreover, genotypes of these species were the most gas-productive ones. The results confirmed that these risk factors should be taken into account in developing strategies in the control of Clostridium spp. spores contamination in ewe milk.