14 May 1999

BE PREPARED FOR END OF NORMAL AGP USES

What can be done to

counteract concerns – and

bans – on antibiotic growth

promoter use? Specialist pig

vet Richard Potter of the

Oxon-based Larkmead Vet

Group gives his views

ANTIBACTERIAL growth promoters (AGPs) have been used for many years to improve livestock feed conversion efficiency and growth rates, and have proven to be an effective and relatively inexpensive way of achieving this objective.

Until recently AGPs have been perceived as safe, but recent concerns over antibiotic resistance in bacteria have led to a change in political opinion. Politicians have embraced the precautionary principle, whereby any perceived threat, even though it may be unsubstantiated by fact, leads to the imposition of a ban just to be on the safe side. This is worrying, as science seems to be ignored if it does not give cast-iron guarantees.

As a result, the number of AGPs available for use in pig production will reduce dramatically. This started with the loss of avoparcin last year, through to the ban of a further four AGPs – tylosin, zinc bacitracin, virginiamycin and spiramycin – this summer.

This is based on concerns about possible transfer of resistant bacteria from livestock exposed to these molecules into the human population. Olaquindox will also be banned later this year. As a result only three AGPs will be available for the pig industry in Europe; avilamycin, salinomycin and flavomycin.

Further changes may be driven by the fact that Sweden banned AGPs some years ago, and that the Danish pig industry imposed a tax on feeds containing AGPs for pigs over 30kg last year. The Danes have undertaken to remove all AGPs in the near future.

Whatever their reasons, they have grasped the fact that by not using these products they have effectively differentiated their product within the market place.

With so many changes in such a short time, many producers have questioned their own use of AGPs, in order that, if there were to be a complete ban, they would be forearmed.

While this may well be sensible, it is important to remember that the Swedish experience of a total ban was an upsurge in enteric problems in growing pigs, and for a period after the ban there was an increase in the overall use of antibiotics.

The situation in Sweden has improved since then, but it highlights the need to approach AGP removal in a structured way in order to avoid a deterioration in performance as a result of disease.

Vets can advise on the options available and ways of minimising risks, while assessing the various issues on each individual farm.

The mode of action of AGPs is varied and complex, and their removal may have an impact on the gut flora of the pig.

The strategy for a particular farm needs to be approached by asking the following questions:-

1. What benefit am I gaining by using AGPs?

Improvements in feed conversion ratio and growth rate claimed for AGPs, although important, are relatively small, and therefore difficult to assess on a farm without carefully controlled and randomised studies.

Other variables

A single trial comparing groups of pigs with or without added AGPs would probably be meaningless and potentially misleading, as there are many other variables that will also affect what is being measured. Your vet will understand the complexities of this and be able to assist in gaining a true assessment of what is currently being achieved.

2. How are AGPs improving performance of pigs in my herd?

Every herd is different and the benefits gained will vary because of this fact. The example of tylosin controlling Ileitis is a case in point. There is now a serological test available to screen herds for the presence of the organism causing this disease, in order to assess and control the risks if tylosin is to be removed.

Olaquindox is recognised as having an effect on controlling post weaning scour and vet investigation of the organisms that cause this problem will allow alternatives to be identified and prescribed.

3. What other options are open to me?

There has been considerable interest in alternatives to AGPs, although there is much still to be learned and a considerable need for scientific trial data. The following points outline the various alternatives that could be considered:-

The interaction between different AGPs in feed is unclear in many cases, and although there is some evidence of an additive effect where AGPs are used in conjunction with prescribed medication, in many cases there is likely to be little change if the AGP is removed from the combination. Many creep rations are medicated to control post weaning disease such as scour, or Glassers Disease, making the additional benefit of AGPs in these rations questionable.

Hygiene affects the enteric health of the pig, and more regular washing and disinfection of accommodation will reduce risk of gut disease.

Batch management assists in improving hygiene, as well as reducing opportunities for disease transmission from older to younger pigs. Improving pig flow is possible on many farms to move closer to a batch management system.

Feed acidification seems to help to promote a healthy gut flora and a number of organic acid preparations for in-feed inclusion are available.

These products offer considerable opportunities to reduce incidence of low-grade scour. Wet feed incorporating acid products such as whey achieve this already, as do fermented liquid feeds for piglets, promoting lactic fermentation to achieve a low pH.

Nutritional adjustments to the ration to reduce non-digestible components leading to an abnormal gut flora should be considered. This includes the use of enzymes to assist in cereal digestion.

There are a number of probiotic products already licensed.

Additives

Unlicensed herbal additives are also available, but feed compounders are unlikely to handle these products unless the manufacturers can supply supporting data. The use of unlicensed additives would also raise issues regarding the various quality assurance schemes.

There are a number of routes that can be followed, and many producers have already reduced their reliance on growth promoters by using these other options. While there are licensed products available these could continue to be used, but it would seem sensible to assess the various issues involved on units using AGPs in order to be prepared if further bans are applied. &#42