New Zealand Journal of Agricultural Research abstracts

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Short communication

Escherichia coli shedding by dairy cows

Andrea Donnison

Colleen Ross

Climate, Land and Environment Section
AgResearch, Ruakura Campus
Private Bag 3213
Hamilton 3240, New Zealand
andrea.donnison@agresearch.co.nz
colleen.ross@agresearch.co.nz

Dave Clark

DairyNZ Ltd
Private Bag 3221
Hamilton 3240, New Zealand
dave.clark@dairynz.co.nz

Abstract Eight non-lactating Friesian cows participated in two metabolic balance trials in which they were fed pasture-silage over 8 days and 6 days respectively. All daily faeces from each cow were collected and analysed for Escherichia coli.On two occasions E. coli was also measured in freshly voided faeces from 21 Friesian cows that grazed fresh pasture. The amount of faeces shed by the silage-fed cows was relatively constant (average 25.8 kg cow^–1 day^–1 (wet weight); SD 4.86 kg) but E. coli concentrations were very variable and no E. coli were recovered from 14% of daily samples. Variation for a single cow was within 2 log₁₀ but between cows it was up to 4 log₁₀. The overall average concentration was 1.1 × 10³E. coli g^–1. The overall average shedding rate (wet weight) was 2.6 × 10⁷ E. coli cow^–1 day^–1 and for individual cows it ranged from 5.0 × 10⁵ to 3.9 × 10⁹E. coli cow^–1 day^–1. E. coli concentrationswere also variable (by up to 3 log₁₀) for the pasture-fedcows, and their overall average was 2.9 × 10⁴E. coli g^–1 (no sample had <10 E. coli g^–1). These findings demonstrate that E. coli shedding by dairy cows is very variable and may be influenced by factors such as diet.

Keywords dairy cows; Escherichia coli;faecal bacteria; shedding rates

A0®; Online publication date 11 August 2008; Received 7 September 2007; accepted 21 May 2008

New Zealand Journal of Agricultural Research, 2008, Vol. 51: 273–278
0028–8233/08/5103–0273 © The Royal Society of New Zealand 2008

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