Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 27, 1998
Publication Date: N/A
Interpretive Summary: Current thought suggests that a certain type of bacteria known as coliforms can be found in high levels in cattle feces. Coliform bacteria are currently used as an indicator for fecal contamination in licensed slaughter plants. Because cows around calving time experience more disese due to coliform bacteria, this research investigated whether fecal coliform shedding in cows around calving time increases. All cows experienced low to even undetectable fecal coliform shedding levels 4 weeks prior to calving. However, within 12 days of calving, fecal coliform levels increased dramatically per gram of feces. We conclude that coliforms, particularly a strain called Escherichia coli, are not always detectable, but can be shed at high levels in the feces of adult cows. From a food safety standpoint, the reliability of using E. coli detection as a monitor for fecal contamination of carcasses may be questionable.
Technical Abstract: Objective: To investigate whether fecal coliform shedding in dairy cows increases during the periparturient period, and to assess any correlation between feed intake changes and fluctuations in numbers of fecal coliforms. Animals: 12 healthy, Holstein cows. Procedure: Two separate studies were conducted. Fecal samples were obtained on a regular basis from approximately 2 months prepartum through the postpartum period. Samples were cultured for total fecal coliforms, and Escherichia coli O157:H7. Additionally, in study 2, daily feed intake was monitored. Results: During the first 2 weeks of sampling, 11 of 12 cows demonstrated low fecal coliform bacteria shedding levels with minimal fluctuations (+/- 2 log10/gm feces). Coliforms were completely undetectable in 4-8% of the samples taken from 7 of 12 cows. All cows experienced a dramatic increase of 104-107 cfu/gm of feces near parturition. Fecal coliform shedding peaked within 7 days of parturition in 9 of 12 cows, and within 12 days in 3 cows. No association with changes in feed intake was observed. No isolates of E. coli O157:H7 were found on selective media. Conclusions: Periparturient cows experience specific periods of increased fecal coliform shedding concurrent with known periods of immunosuppression which may contribute to the high incidence of coliform mastitis. Other than the increases in fecal coliforms seen near parturition, adult cows do not shed high levels of coliforms in their feces nor are coliforms always detectable by conventional culture methods.