The researcher presented her study at Teagasc’s Milk Quality Conference in Tipperary today.
The objective of the study was to determine the on-farm management factors that are associated with the Bacillus cereus count in raw bulk tank milk.
Courtesy of her presentation, O’Connell outlined the research approach. “Bulk tank milk quality was monitored for B. cereus on 63 dairy farms between July and August 2012. Bulk tank milk samples corresponding with processor milk collection dates were taken over a two-week period prior to the farm visit and tested for B. cereus.
“The four most recent samples taken prior to the on-farm visit were averaged and log transformed to give the outcome variable; mean log10 B. cereus cfu/ml.”
On-farm data collection included recording observations and providing a questionnaire on basic hygiene, management factors and cow hygiene scoring, she added.
In terms of results, the study found that the geometric mean B. cereus count for all farms was 40 cfu/ml. The start temperature of the cleaning solution wash, dry wiping teats prior to unit application, the feeding of silage and re-using the cleaning solution more than once were all unconditionally associated (P<0.10) with the B. cereus count in bulk tank milk but did not enter the final multivariable model.
O’Connell explained: “B. cereus count was four times greater (201 cfu/ml) when cows had been housed compared to when they were on pasture (50 cfu/ml). The allocation of fresh grass every 12 h (62 cfu/ml) resulted in a decrease in B. cereus count (166 cfu/ml every 24 h or greater).”
The research also found the testing of water for bacteriology was associated with an increase in B. cereus count.
In concluding, O’Connell noted the study highlights that specific management factors associated with the B. cereus count in bulk tank milk.