Antibiotics are used in production animals to treat disease, as a preventive of future infection and for performance enhancement (to increase yield or speed growth).
Despite huge successes, antibiotic use in food production animals is increasingly problematic. Drug residues can enter the human food chain, mainly affecting production of processed foods e.g. yoghurt, and occasionally results in allergic responses in consumers. However, these issues can be managed by strict adherence to drug withholding periods.
More important now is the growing consumer concern about antibiotic use and the resulting political pressure to restrict the use of antibiotics in food animals.
Internationally, use of antibiotics in food production animals is gradually becoming prohibited. It’s likely to become more restricted in New Zealand, eventually, as well.
Some advocates even call for antibiotics to be banned because of fears their use leads to faster emergence of bacteria carrying genes for antibiotic resistance. As a result, a number of antibiotics, such as chloramphenicol and nitrofurazone, have been reserved for human and companion animals (pets) for some years already.
Regulatory bodies worldwide are now moving to increase this list to include, in particular, the most modern generation of a group of antibiotics known as cephalosporins.
The lack of good scientific evidence that antibiotics have positive ‘growth promotion’ benefits, and the increasing incidence of bacteria with resistance to antibiotics, has already led to ‘growth promoting’ products being banned in many countries.
This process started in Sweden in 1986 and in 2006 the EU placed a total ban on the use of a number of antibiotics for performance enhancement, with no obvious adverse effects on production resulting.
Dairying has always been sparing in such use and in New Zealand their selective application can be easily classified as disease prevention e.g. treatment of weaner calves with a coccidiostat in late spring.
In adult cows the predominant use of antibiotics is the treatment and prevention of mastitis, for which penicillin-type products and cephalosporins are primarily used. It is virtually impossible to argue against treating acute clinical mastitis.
The ‘Five Freedoms of Animal Welfare’ include Freedom from Pain, Injury or Disease – by prevention or rapid diagnosis of disease and suitable treatment. In 1997, the International Dairy Federation adopted a resolution that ‘mastitis therapy is necessary for animal welfare’. New Zealand dairy farmers are pragmatic in their approach to treatment and do not use therapeutic antibiotics unnecessarily.
Considerable evidence exists that many mild cases of mastitis will self-cure and treatments are reserved more for acute cases where there is associated pain and inflammation.
Dry cow treatments
Much more contentious is the use of prophylactic antibiotics. For dairy farming, this includes dry cow treatments (DCT). DCT was partly developed to cure subclinical infections present at the end of lactation. It has never proven worthwhile to try and cure them during lactation. It has consistently been found to be up
to 80 percent effective in achieving cure during the dry period, one of the highest performance rates for any form of antibiotic treatment. However, a blanket treatment approach means that antibiotics are administered to many animals that have no intramammary infection.
The other motive in development of DCT was to prevent up to 80 percent of new infections that may occur in the dry period (half of all new infections of the mammary gland occur in the dry period).
It is not difficult to find cows with clinical mastitis and their treatment can be easily justified. But it is very difficult to predict which 10-20 percent of animals are likely to develop a totally new infection during the dry period, so many animals receive antibiotic treatment simply as insurance. This has been shown to be practical and economically worthwhile. As pressures increase to reduce antibiotic use in animals, DCTs have become a primary target for change, because uninfected animals are treated.
By 2009, the Dutch found that banning of antibiotic growth promoters had not reduced the total tonnage of antibiotics used in food animals. They then mandated for a 50 percent reduction in treatment use of antibiotics in food animals over three years.
On January 6 2012, the US Food & Drug Administration issued an order that prohibits certain uses of cephalosporin drugs in food-producing animals. This ban includes unapproved doses, frequencies and durations, i.e. off-label use.
The order also prohibits using cephalosporin drugs for disease prevention, but whether or not this will include the use of cephalosporin DCT remains uncertain.
Then on January 12 the German authorities published draft legislation to ‘reduce to an absolute minimum’ use of antibiotics in animals heading for slaughter into the food chain. The momentum to change the way that animal farming uses antibiotics is clearly gaining pace and scale.
This is happening in our international marketplaces and for our international competitors. The need for and extent of regulatory change in New Zealand is the responsibility of the New Zealand Food Safety Authority, but they generally follow international trends. It seems inevitable that antibiotic use in food-producing animals will become more restricted here as well.
Dairy farmers will need to review their use of DCT as part of their annual animal health plan prepared with their veterinarian.
Fortunately, New Zealand research studies have allowed us to understand the value, limitations and alternatives to antibiotic DCT.
These learnings, along with significant international work, are being incorporated into the new DairyNZ SmartSAMM mastitis control programme being progressively released.
A review of the evidence on best ways to manage dry cow mastitis prevention will appear in the April 2012 issue of the DairyNZ Technical Series.
The future of mastitis management
- International marketplaces and international competitors are changing how their animal farmers use antibiotics
- Regulatory change in New Zealand is the responsibility of the New Zealand Food Safety Authority, which generally follow international trends
- It seems inevitable antibiotic use in food-producing animals will become more restricted here as well
- Dairy farmers will need to review their use of DCT as part of their annual animal health plan prepared with their veterinarian
- New Zealand research studies and international work is being incorporated into the new DairyNZ SmartSAMM mastitis control programme being progressively released.
Find out more about it at dairynz.co.nz/smartsamm
This article was originally published in Inside Dairy March 2012