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The search for antibiotic growth promoters casts a wide net with various additives exhibiting a number of nutritional traits. © Photographer: Andrija Kasom | Agency: Dreamstime.com
on January 3, 2008

Search for replacement additives casts a wide net

Nutritionists and pig scientists in Europe have identified no single replacement for antibiotic growth promoters.

By general consensus among nutritionists and pig scientists in Europe, there is no one single ‘magic bullet' replacement for antibiotic growth promoter (AGP) use. Either the individual items tried have not given the degree of response needed or they have failed to deliver consistent effects, at least as much for protecting the health of the animal as for boosting growth performance.

Response is varied

Researchers questioned by Feed International have typically put organic acids and betaine highest on their list in terms of reliability while usually expressing caution over the particular probiotics they had tried. Herbal extracts and essential oils were often called too varied as groups to generalize on their effects.

These research scientists were especially united in their view that we should expect to see European Union action imminently against zinc oxide and copper sulfate inclusions in pig feeds on the grounds of environmental pollution by the metals excreted in manure.

So far, zinc oxide has been a particularly effective weapon in controlling diarrhea in weaned pigs a notable health problem when antibiotic growth promoters were removed. According to the scientists, extra thought will have to be given to the influences of feed structure and protein levels as well as to possible health-protecting ingredients when zinc oxide disappears from the permitted list.

Summary of additives

The remarks about zinc oxide are worth bearing in mind when considering an analysis of alternatives to antibiotic feed additives for pigs that was prepared in the UK by Dr Pinder Gill of the Meat and Livestock Commission with assistance from the MLC's Derek Armstrong and the University of Aberdeen's Dr Vernon Fowler, on behalf of the British Society of Animal Science or BSAS. A chart from that analysis is reproduced here with Dr Gill's permission. At his request, the original is also amended by now including liquid feeding of young pigs.

Dr Gill says a review of the scientific literature suggests that, in general, alternative additives provide little consistent growth benefit. Among the more promising are organic acids, fermentable substrates and enzymes, but no single substance currently could replace the function of feed antibiotics. Since the growth benefit found from feeding antibiotics is achieved through many different effects on the gut, the strategy for replacing them will depend on a combination of nutritional, housing and husbandry factors.

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