The use of on-farm culture systems for making treatment decisions Kimberley MacDonald, BSc, DVM CBMRN - Maritime Quality Milk Atlantic Veterinary College UPEI Colloque santé des troupeaux laitiers November 25 th 2009
Outline Introduction The mastitis picture in Canada Methods Brief description of the trial Preliminary results Accuracy Clinical and bacteriological cure rates Economic analysis Petrifilm storage conditions Conclusions
Purpose Mastitis #1 reason for antibiotics Pathogens causing mastitis Coliform bacteria: high self cure rate Elimination of bacteria: at time of diagnosis Gram positive infections: up to 60% of cases Susceptibility to antibiotics On Farm Culture Rapid results (22-24 hours) Convenient and easy to use
Purpose Use of a mastitis culture system Informed decisions Target gram positive cases Reduce antibiotic use Reduce milk discard Lessen residue concerns **Not compromise the health/mastitis risk**
On-Farm Culture Project Clinical trial Cases randomly assigned to: 1) Culture group Treatment according to results in 24 hours 2) Treatment group Immediate treatment ***Treatment: Cefalak: 2 tubes 12 hours apart***
Key Information Collected Dates Onset of mastitis Date milk returned to normal (clinical cure) Date milk returned to tank (economic impact) Bacteriology On farm results (accuracy) Lab results (bacteriologic cure) Production (DHI) Records (economic impact)
On-Farm Culture Project Enrollment of cows 719 eligible records received from 48 farms Clinical mastitis cases Temperature <39.5 C Mild (milk abnormal, quarter normal) Moderate (milk abnormal, quarter abnormal) ***Not for sick cows (off feed, temp. > 39.5 C)***
Preliminary Results From the culture project raw data 36% cases did not receive antibiotics Distribution of pathogens (standard bacteriology) 55% of cases are gram positive 24% of cases are no growths 11% of cases are coliforms 9% contaminated 1% yeast/fungi/mold
Accuracy On-Farm Compared farmers results to lab results 66% Sensitive (66% of Gram positive cases detected) 66% Negative Predictive value (66% of cases that were diagnosed as Coliforms or non-significant growths actually were) Culture system has 93.8% Se and 89.7% NPV capabilities with better training
Accuracy Why lower accuracy on farm than in lab? Environment: Requires designated lab area of barn or house Dry and clean Avoid contamination Technique Avoid contamination from hands, milk sample etc Interpretation Better training on identifying colony growth
Clinical and Bacteriological Cures Interested in Differences in Cure rates Between Culture and Control group cases Clinical Cure (yes/no) Milk returned to normal appearance Using protocol provided Bacteriological cure Causative organism (on initial milk sample) Not cultured on either follow up milk sample
Clinical and Bacteriological Cure Failure to achieve clinical cure Require additional antibiotics to cure Became sick Failure of milk to return to normal Culled or dried off due to mastitis Failure to achieve bacteriological cure If organism cultured on either follow up sample Follow up done at 14-21 and 28-35 days following onset of clinical case
Cure rates (%) - Preliminary Results Culture Group Treatment Control Group Clinical Cure 85.2 88.5 Bacteriologic Cure 80.9 83.7 * No statistically significant difference between groups
Days to Clinical Cure What is the risk of selectively treated cows? In the culture group Compared to Control group cases The number of days to achieve clinical cure
Days out of tank Marketable milk Differences between culture and control group cases Average days out of the tank
Economics Partial Budget Analysis Costs Discarded milk Treatments Culture system Milk production loss 0.5 kg/milk/day for each linear score of 5+ (SCC of 200k)
Storage Trial Petrifilms stable at room temperature* 1 year + Must avoid humid/hot conditions Packaging change Proved experimentally Recommendations for storage and use: Office or house Avoid parlor and milk house
Further Analysis In depth look at the data Further statistical analysis on: Clinical and bacteriological cure rates Economic evaluation Additional work Antimicrobial resistance testing See if resistance more likely in: Control Group cases Certain organisms
Where we are today MQM Mastitis treatment decision system Now available for purchase Step by step instructions (en français aussi!) Complete culture system Vials to submit to the lab for bacteria id Contact: Art Gennis Maritime Quality Milk 902-566-6489
Funding and Support This research was financed by the Natural Science and Engineering Research Council, Alberta Milk, Dairy Farmers of New Brunswick, Nova Scotia, Ontario and Prince Edward Island, Novalait Inc., Dairy Farmers of Canada, Canadian Dairy Network, Agriculture and Agri-Food Canada, Public Health Agency of Canada, Technology PEI Inc., Université de Montréal and University of Prince Edward Island, through the Canadian Bovine Mastitis Research Network. Also funded by Prince Edward Island Department of Innovation and Advanced Learning
Acknowledgements Dairy Farmers Technical support team (CBMRN, MQM, AVC) Wyeth Animal Health 3M Microbiology Collaborators: Greg Keefe, Ian Dohoo, Jean-Philippe Roy, Ken Leslie, Anne Muckle, Doris Poole