Blanket Feeding of Antimicrobials
28 May 2010
Blanket feeding of antimicrobials in milk to calves could be putting their lifetime health at risk says Dai Grove-White, of the University of Liverpool Vet School.
Antimicrobials, better known to some as antibiotics, have been a vital weapon in dairy farmers’ armory. They either kill or prevent multiplication of sensitive bacteria.
Introducing antimicrobials to milk, chiefly chlortetracycline, to pre-weaned calves was a popular strategy in the 1970s. It was believed to be helpful in controlling disease in early life. Nowadays feeding milk to calves which contains antimicrobials is of particular concern since the concentrations fed and the duration of feeding are known as being potent inducers of multiple drug resistant bacteria. For example, Salmonella spp and E. coli resistant bacteria have been reported on many occasions.
Bacterial resistance develops simply because bacteria are incredibly rapidly dividing with a generation time measured in minutes. This means that evolution and selection of strains resistant to an antibiotic can, and does, develop rapidly. Antibiotic resistance is now a major human as well as animal health concern; for example MRSA occurs in humans due to the bacterium developing resistance to almost all antibiotics such that it is almost completely untreatable. In addition, Campylobacter spp, a major cause of diarrhoea in humans acquired chiefly from poultry meat is increasingly becoming resistant to the fluoroquinolone group of antibiotics due to their widespread use in poultry production.
To compound the problem, drug resistance can be transferred between different bacterial species and this often occurs en masse with transfer of resistance genes to a wide range of bacteria. Whilst every dose of antimicrobial has the potential to select for resistance, of particular concern is long term administration of low levels of antimicrobial, or so called sub-therapeutic doses, which have been shown on countless occasions to be potent drivers for the development of resistant strains.
Notwithstanding, antimicrobials continue to remain exceptionally valuable drugs and to preserve their efficacy they should be used correctly which generally means ensuring an adequate dose targeted against the germ in question. Current best practice is to identify and test the pathogen in the laboratory to determine which antimicrobial to use against it.
To feed antimicrobials routinely to calves is at best a ‘sticking plaster’ on a problem, and the practice should be discouraged by all who are involved in animal health. However the issue of antimicrobial resistance is posing a new threat to calf health since the increased adoption of group calf feeding systems has encouraged introducing chlortetracycline in milk.
The right to prescribe and use antimicrobials in animals is vital for modern agriculture. However, we only have that right on condition that we use them responsibly; feeding antimicrobials routinely is not responsible and there are plenty of bodies outside agriculture who would like to restrict their usage. Irresponsible use plays into their hands.
The answer is NOT to feed antimicrobials – they may provide temporary relief but are contributing to the danger of antimicrobial resistance and furthermore not actually solving the underlying health problems.
Calf health, a preventative approach
Farmers can take a preventative approach to calf health by introducing the following seven point plan, according to Volac’s calf technical specialist Maggie Gould. “Adopting these measures will greatly reduce the need to introduce blanket in-feed or in-milk medication to groups of calves,” she says. “By adopting this responsible policy in calf management, the risk of developing drug resistant bacterial strains is reduced and the potential to improve long term performance will be maximised.”
Ensure an early and adequate intake of good quality colostrum; a minimum three litres in the first six hours of life. Remember a calf requires approximately 20 minutes of continuous suckling to consume those three litres.
Practice group rearing with an all-in, all-out policy. Clean and disinfect between batches.
Avoid mixing established groups and keeping animals of widely different ages in the same airspace.
- Keep calf pens clean, dry and well bedded with good quality, barn stored straw.
Ensure adequate ventilation, with no draughts. Air outlets (0.04m2 per calf) should be 1.5 – 2.5m above the inlet (0.045m2 per calf) to allow good air movement to target more than 6 air changes per hour. Use a smoke bomb to check if unsure.
Provide high quality nutrition; i.e. sufficient milk replacer, concentrates and ad-lib clean, fresh water.
Employ appropriate vaccination and health management strategies as advised by your vet.
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