23 Dec 2013

MPI investigates dairy antibiotic use

5:16 pm on 23 December 2013

The Ministry for Primary Industries will be investigating the increased use of an antibiotic used to treat mastitis in the dairy industry to see whether a trend is emerging.

A ministry survey found that while antibiotic sales in agriculture decreased by 19% between 2009 and 2011, there was a significant increase in the use of injectable tylosin in dairy cattle to treat mastitis.

The ministry says it's important the increased use is investigated to limit the potential risk of antibiotic resistance emerging.

The ministry monitors antibiotic use, looking in particular for signs of antibiotic resistance in food-producing and companion animals.

The Veterinary Association's president, Steve Merchant says getting to the bottom of changes in antibiotic use is important to ensure they're being used appropriately.

Mr Merchant says for instance the increased use of injectable tylosin, for treating mastitis in dairy cows, may be related to the expansion of the dairy industry and increase in dairy cow numbers.

Mastitis is inflammation of the udder caused by infection.

Antibiotics are used for mastitis prevention as well as treatment.

Dairy New Zealand's chief scientist Eric Hillerton says the emphasis in the industry here is preventing the disease through good herd management, an approach that's appears to be working, compared with results in other countries.

He thinks the evidence surrounding mastitis treatment and antibiotic resistance is debatable.

He says it's a hugely contentious area both in society and in human and veterinary medicine and the evidence is quite vague.

Dr Hillerton says the National Mastitis Council based in the United States has a report saying there is no evidence that use of antibiotics to treat mastitis has in any way changed antibiotic resistance in these bacteria.