Note: Thermophilic campylobacters in dairy slurries on Lancashire farms: seasonal effects of storage and land application

Abstract

Slurry storage tanks on Lancashire farms were sampled in May, June, October and November. There was a seasonal pattern in the number of thermophilic campylobacters. The average log10 MPN per gram fresh weight (log10 MPN gfw−1) in stored samples in May and June was 0·78 (S.D. 0·71) compared to 2·07 (S.D. 0·70) in November and December. Campylobacters were readily detected in samples of mature slurry and composted bedding that farmers were about to put to land. The survival of campylobacters in slurry sprayed on land was studied in two seasons. In June, on farm A, stored slurry was mechanically aerated for 48 h and very low numbers of campylobacters (0·9 log10 MPN gfw−1) remained in the slurry before it was sprayed onto land. They became undetectable within 24 h once sprayed on land. In contrast, campylobacters in matured but unaerated slurry that was sprayed onto land on farm B in February were still detectable in samples taken 5 d after application to land, dropping from 2·11 log10 MPN gfw−1–1·37, a decline of only 0·74 log10 MPN gfw−1 in the first 5 d after application.