Pasteurized milk fed to calves should contain fewer pathogens than unpasteurized milk, but poor hygiene practices at many levels can lead to pathogen-loaded milk for young calves.
When investigating potential pasteurized milk contamination and pathogen loads, dairy calf expert Sheila McGuirk, DVM, PhD, University of Wisconsin, typically starts at that end of the pasteurization process. “I want to know what is the level of bacterial contamination that is coming to the calf,” she says. “If it’s clean in the bucket, then the testing is finished. If the milk is contaminated there, I’ll back track and check standard plate counts as the milk leaves the pasteurizer.”
If that is high, McGuirk checks pre-pasteurization counts. “The frequency of monitoring depends on the number of calves or the threshold of concern,” she says. “Monthly testing is a good start. We found one that had a thermophilic Strep. growing in the pasteurizer. Relative to the calf health, maybe it wasn’t such a concern, but health had slipped during the time, and we got back into the function of the pasteurizer and found where it was coming in.”
Dairy veterinary consultant Scott Smith, DVM, The Dairy Authority, LLC, Greeley, Colo., recommends his dairy clients do bacteria counts on their pasteurized milk at least twice a month. “Then from time to time, we’ll come in at the nipple end and take a culture to see what the calf is being presented with,” he explains.
“That is way more critical in a lot of cases than how pathogen load looks at the tank level,” Smith adds. “Post pasteurized bacteria counts can look great at the tank level, but if they’re doing a poor job of hygiene with their bottle management or bucket management, by the time the calf sees the milk, counts can be higher than pre-pasteurized levels.”
This information is from a Bovine Veterinarian dairy diagnostics roundtable sponsored by Intervet/Schering-Plough Animal Health.