New test to detect antibiotic resistance in dairy cows

Cognosco managing director and dairy veterinarian Dr Scott McDougall and Bayer dairy veterinarian Dr Ray Castle. Photo / Supplied.

An initiative that involves the testing of bulk milk supply for antibiotic resistance will allow farmers to more effectively treat mastitis in New Zealand, says Bayer.

Known as Dairy Antibiogram, the test will allow veterinarians to determine if antibiotic resistance to a mastitis treatment is present on a farm. If resistant bacteria are present, then the veterinarian will be able to prescribe a more effective antibiotic.

Bayer dairy veterinarian, Dr Ray Castle said mastitis was a significant problem for dairy farmers and the country's 5 million cows.

"Mastitis infects between 10 and 20 per cent of the national dairy herd at a treatment cost of up to $250 per cow. As a veterinarian you want to make sure you're using the right antibiotics in the most responsible and effective way possible, which this test will allow.

"At the moment, we actually don't know how big a problem antibiotic resistance is in New Zealand. The Dairy Antibiogram test will give us some of that insight," says Dr Castle.

Dr Castle has been working on the testing and reporting methodology since becoming aware of a similar programme being run in the Netherlands in late 2016.

The technology involved had to be specifically adapted for New Zealand by Bayer, working in conjunction with R&D organisation Cognosco, which has been contracted to do the testing.

As part of a consultation with a farmer, a veterinarian can request a sample of milk be sent from the milk producer to the lab. The test is performed and the results sent back to the veterinarian, who can then prescribe an appropriate antibiotic. Turnaround time is approximately three to four weeks.

Cognosco managing director and dairy veterinarian, Dr Scott McDougall, said the Dairy Antibiogram test was an important development for the dairy industry.

"Currently there is no ongoing surveillance program for antibiotic resistance in the dairy industry in New Zealand and relatively few milk samples are submitted for antibiotic resistance testing.

"This means that the majority of the time veterinarians are prescribing without knowing either the pathogen or its sensitivity to antibiotics. There is a risk of ineffective therapies being used.

"Dairy Antibiogram provides us with an easy way of screening for antibiotic sensitivities in dairy herds, which will lead to more prudent use of antibiotics across the dairy industry

"Over time we will develop an understanding of resistance patterns across the country, potentially identifying if there are emerging problems with antibiotic resistance enabling us to then focus our attention on these herds."

Dr Castle says ideally he would like to see all dairy farms in the country have their milk undergo the Dairy Antibiogram test.

"Antibiotics are an important tool in keeping our dairy herds healthy, but we need to ensure they're not overused and that they are actually working."