Cow-calf producers are being careful with antimicrobials — and that’s a good news story the industry needs to share with consumers, says one of the researchers of a groundbreaking study of cattle production on the Prairies.
The cattle health network, which has been tracking production practices of more than 100 cow-calf producers since 2012, found only 20 per cent of them use antimicrobials of high importance in human medicine in a given year.
“That doesn’t mean that they used them a lot,” said Cheryl Waldner, co-investigator in the study and professor in large-animal sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.
“They could have used them only once. Most of the producers are not using Category 1 drugs ever in cows or pre-weaned calves.
“We have to be very careful and cautious and look for opportunities to minimize use, but this tells us that we are certainly doing that. It is a good news story. We are being prudent with our use in cow-calf herds.”
The study has found that antimicrobials were generally used to treat lameness in cattle, reproductive infections, eye infections, and respiratory diseases. Injectable oxytetracycline, penicillin, and flor-fenicol are the most commonly used antimicrobials in cows, while tetracycline and sulfa drugs are commonly used to treat calves.
“Most of the drugs used by cow-calf producers are Category 3 drugs, so they are pretty far down the list in terms of importance to human health,” said Waldner.
It’s also rare for producers to add antimicrobials to feed. Fewer than 15 per cent of the producers surveyed said they had added antimicrobials to feed, and producers who did said they used them for very short periods of time.
About half of the producers surveyed said that they think about antimicrobial resistance when choosing a product to treat their cattle.
The last time a study on antimicrobial use and resistance was conducted was back in 2002, when Waldner and other researchers collected data from 200 herds.
As part of the cattle health network study, local veterinarians collected fecal samples from 20 randomly selected cattle in about 100 herds in the fall of 2014. These samples were pooled, and E. coli and campylobacter were grown from the samples.
Resistance was pretty low. Only about 10 per cent of herds had one resistant organism.
“It’s not the majority of herds — it’s the minority of herds where we are seeing resistance,” said Waldner.
However, about 2.5 per cent of isolates were resistant to three or more antimicrobials.
“It’s not very common, but there is some evidence of multiple resistant organisms out there,” she said. “It’s a reminder to be cautious and that we need to continue to pay attention to this issue.”
The most common resistance is to tetracycline, which is expected since it’s the most commonly used antimicrobial.
Herds with the most antimicrobial resistance had higher calf mortality in the spring, and would have had a higher use of antimicrobials as a result.
“Herds that had more problems with the spring calf crop were the ones more likely to have higher levels of resistance,” said Waldner.