|CARTER, BOONE - New Mexico State University|
|FARROW, RUSSELL - Texas A&M University|
|ISLAS, ALFONSO - New Mexico State University|
|HAGEVOORT, ROBERT - New Mexico State University|
|FRIEND, TED - Texas A&M University|
Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2010
Publication Date: 3/1/2011
Citation: Edrington, T.S., Carter, B.H., Farrow, R.L., Islas, A., Hagevoort, R.G., Friend, T.H., Callaway, T.R., Anderson, R.C., Nisbet, D.J. 2011. Influence of weaning on fecal shedding of pathogenic bacteria in dairy calves. Foodborne Pathogens and Disease. 8:395-401.
Interpretive Summary: Dairy cattle may contain the bacteria E. coli and Salmonella that can make people sick. Stress in dairy cattle may increase fecal shedding of bacteria. Weaning dairy calves from milk to solid feed may be stressful to the calf or alter the intestinal environment in a way that would favor certain bacteria. We examined the effect of weaning on fecal shedding of E. coli O157:H7 and Salmonella by sampling calves before and after weaning. Results of these experiments showed that weaning did not increase the prevalence of either of these pathogenic bacteria, nor did it affect the ability of antibiotics to kill these bacteria.
Technical Abstract: The objectives of the current research were to determine the effect of weaning on fecal shedding of Salmonella and E. coli O157:H7 in dairy calves and to examine cultured isolates (to include Enterococcus) for antimicrobial susceptibility. This research was conducted on one large commercial dairy (> 3000 head) in Southwestern United States. Two collections were made during the winter (January 2009) and summer (July 2009) seasons. For the winter collection, two groups of calves were sampled (group 1: n = 18 pens, 69 head, approx. 12 weeks of age; group 2: n = 19 pens, 75 head, approx. 10 weeks of age). Fecal samples were collected from all calves via rectal palpation two days pre- and again two days post-weaning. For the summer collection, one group of calves housed in 40 pens were utilized and 79 and 76 calves sampled 7 days pre- and 5 days post-weaning, respectively. Fecal samples were collected into sterile palpation sleeves, placed on ice, and shipped to our laboratory for bacterial culture of E. coli O157:H7, Salmonella, and Enterococcus. Antimicrobial susceptibility was determined on select isolates. No differences (P > 0.10) in prevalence of Salmonella or E. coli O157:H7 were observed due to weaning in the winter collection. In the summer collection, more (P < 0.01) fecal samples were Salmonella-positive pre-weaning (15.2%) as compared to post-weaning (2.6%). No differences were observed for antimicrobial susceptibility in isolates collected pre- as compared to post-weaning in either winter or summer collections. Results of the current research indicate that the weaning of dairy calves does not significantly influence pathogenic bacteria or modify antimicrobial susceptibility profiles of these bacteria.