Using tannins from local trees

Scientists in Nottingham University have successfully used tannins, both in feed and as a drench, in both temperate and tropical sheep to reduce worm numbers.

This sort of information is vitally important to poor farmers keeping goats and sheep in mixed flocks. It means that they can firstly find a very cheap environmentally sound replacement for expensive synthetic drugs. This immediately avoids drug resistance now common in developing countries.

It also means that in mixed flocks of sheep and goats the total worm parasite problem is likely to be focused on the sheep as goats appear to be able to tolerate the problem because they, if allowed to browse, will have already selected tree species that contain tannins. The farmer by treating the sheep with tannins will make great strides towards reducing the total impact of intestinal worms in the flock. By just having to treat the sheep the cost of preventing parasitic worms will be reduced. This will encourage even the poorer farmers to attempt treatment and reap the benefits.

Using naturally occurring constituents in forages is a potentially cheap and environmentally safe alternative to synthetic chemicals. Tannins, which are naturally occurring secondary metabolites in plants, can reduce worms.

Research at Nottingham University has shown that putting the condensed tannin from quebracho (a product used in the leather industry) into sheeps' diets reduces worm egg output and worm numbers in sheep infected with Trichostrongylus colubriformis worms. The scientists then tried wattle tannin on sheep and succeeded in reducing egg counts by a massive 75% and worm numbers by 87% for Haemonchus worms and 28% for Oesophagostomum worms.

They also found that in Tanzania drenching does not work on goats. This is likely to be due to the different parasite burdens in sheep and goats. The differences between goats and sheep may be because the goats are already adapted to tannins as they traditionally browse forage high in tannins and their guts consequently contain protozoa that are already tolerant to tannins. These protozoa are able to neutralize the tannin effects so they have less effect on the intestinal nematodes. Sheep, being predominantly grazers, normally have a diet that includes a much lower level of tannins.

In Tanzania the scientists used a commercial tannin produced locally from the bark of a tropical tree called Acacia mearnsii. Sheep got a daily dose of drench for just 3 days relevant to their body size.

Further work is underway to see if sheep fed on the dried leaves of the tannin rich Acacia tree (A. polyacantha) will have the same effect.

This information is of immense value to farmers as the tannin power is cheap and readily available as it is already produced for the tanning industry.

The benefits from treating sheep and goats against parasitic worms so that they can maximize the nutrients contained in their feeds or grazing are enormous. Less worms means more milk which gives better young stock. More meat comes from better grown animals and more manure is produced. Animals that are not carrying heavy worm burdens are fitter and more able to combat other disease. They reproduce more often and are easier to manage. All of these plus points could positively influence the livelihoods of poor rural families, especially the children and women who look after smallstock. Rural families would have better nutrition, more produce to sell or to trade and thus a potentially improved livelihoods.

There are potential costs in using tannin extracts to combat worms but at present these are considered to be minimal. The actual cost of products to treat stock is low and the effort in using them on a routine regular basis is small.

There may be potential long-term toxic effects to sheep if given too much tannin drench over a long time. The scientists still have work investigating to see if feeding tannin rich leaves is a better approach. They also need to find the best treatment for goats which currently do not respond well to drenching.

Vets and farmers are very keen to find cheaper alternative methods to control worms to help poor rural families keeping small ruminants. As well as the nutritional manipulation outlined above there is potential for selective breeding to produce sheep and goats that are more resistant to worms. There are also opportunities for the management of grazing in a way that reduces the exposure of livestock to worms on infected pastures. However, this is particularly difficult where pasture is communally used.

The impact of this type of information is potentially enormous. Not only is the product readily available and cheap - it is also simple to use. The approach is thus likely to be self-sustaining once kick started. The incomes and livelihoods of poor families who look after the sheep and goats are likely to substantially change for the better. The approach also has application throughout similar areas in Africa where the leather industry commonly uses tannin products.

This information is part of a series on small stock that cover disease-nutrition interactions.