|Nisbet, David - Dave|
Submitted to: Agriculture, Food and Analytical Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2011
Publication Date: 10/10/2011
Publication URL: http://handle.nal.usda.gov/10113/57359
Citation: Farrow, R.L., Edrington, T.S., Carter, B.H., Friend, T.H., Callaway, T.R., Anderson, R.C., Nisbet, D.J. 2011. Influence of winter and summer hutch coverings on fecal shedding of pathogenic bacteria in dairy calves. Agriculture, Food and Analytical Bacteriology. 1:98-104. Interpretive Summary: Dairy cattle may contain the bacteria E. coli and Salmonella that can make people sick. Dairy calves are typically housed in hutches until after weaning, which provide shelter from inclement weather. Temperature extremes, hot and cold, are still stressful to the calves, even with the hutches. Stress in dairy cattle may increase fecal shedding of bacteria. We examined the effect of modifications to the hutches to reduce the effects of extreme hot and cold temperatures on fecal shedding of E. coli O157:H7 and Salmonella. Results of these experiments showed that the changes made to the hutches resulted in slight differences in fecal prevalence of the above pathogens and may be related to the amount of time the calf spends inside the hutch.
Technical Abstract: The effects of hutch coverings utilized during the summer and winter months to moderate extreme temperatures were examined on fecal shedding of E. coli O157:H7 and Salmonella in newborn dairy calves. Two studies were designed where individual calf hutches were modified with a hutch blanket (treatment) or no hutch blanket (control) in the winter study, and a ventilated hutch design was added as a third treatment in the summer study. A third study examined the effects of shade using screens in three treatment groups: control (no shade [n = 14]), partial shade (n = 4), and full shade (n = 6). Fecal samples were collected on multiple occasions throughout the duration of each study via rectal palpation or from freshly voided fecal pats. Samples were shipped overnight to our laboratory for quantitative and qualitative culture of E. coli O157:H7 and Salmonella and qualitatively for Enterococcus. Isolates (E. coli O157:H7, Salmonella, and Enterococcus) were evaluated for antimicrobial susceptibility. During the summer experiment, prevalence of E. coli O157:H7 and Salmonella was low; however, Salmonella was increased (P < 0.05) in the ventilated hutch compared to the control treatment. Five different Salmonella serogroups were identified, and susceptibility screening determined that all isolates were susceptible to the panel of antimicrobials. There was a tendency (P = 0.06) for a higher percentage of E. coli O157:H7 positive samples in the hutch blanket treatment compared to control and ventilated treatments. In the winter study, quantifiable results for both E. coli O157:H7 and Salmonella were largely negative; however, a numerically higher percentage (26.7% vs. 5.6%) of enriched E. coli O157:H7 samples on d 56 were from the hutch blanket treatment. Antimicrobial susceptibility was conducted on the E. coli O157:H7 isolates, and all were resistant to sulfisoxazole, and two were additionally resistant to streptomycin. Salmonella-positive samples were numerically higher following enrichment; however, no significant treatment differences were observed. Due to the limited number of Salmonella-positive samples, isolates were not examined for antimicrobial susceptibility. Most Enterococcus isolates collected during the winter study were susceptible to all antibiotics, with the exception of quinupristin/dalfopristin, to which all but three were resistant. However, some Enterococcus isolates displayed multiple-drug resistance with no difference being observed by treatment group. In the third (shade cloth) study, fecal samples were collected on three occasions, and all fecal samples were E. coli O157:H7 negative. Salmonella was cultured from all treatment groups; however, no significant differences were observed between treatments. Two isolates from each Salmonella-positive sample were serogrouped, and several isolates yielded different serogroups within the same sample. Although these results would indicate that hutch coverings may contribute to increased pathogen loads in newborn calves, it is possible that a more comfortable hutch environment corresponds with an increased amount of time spent in the hutch, and consequently, an increase in the amount of feces within the hutch. Antimicrobial susceptibility testing did not identify any pathogens with resistance to antimicrobials used in human medicine.