Abstract :
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.
