Escherichia coli shedding by dairy cows

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 × 10³ E. 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 × 10⁹ E. coli cow^‐1 day^‐1. E. coli concentrations were also variable (by up to 3 log₁₀) for the pasture‐fed cows, and their overall average was 2.9 × 10⁴ E. 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