Legume could combat worm problem

Routine use of vet products to counter gastro-intestinal parasites in sheep has traditionally been the option of choice for many producers. But factors including the emergence of new helminth parasites resistant to pharmaceutical wormers are putting pressure on farmers to find alternative approaches.

Fortunately, research by the Institute of Biological, Environmental and Rural Sciences at Aberystwyth University could provide a viable new option. A study by Christina Marley has discovered tannins contained in the legume birdsfoot trefoil (Lotus corniculatus) are extremely effective in reducing parasitic infection.

The tannins work in a number of ways, including a direct reduction of parasites in the animal, a positive impact on parasite larvae in pasture and an indirect boost to the sheep’s immune system.

Tannins in the legume bird’s foot trefoil could help control intestinal parasites in growing lambs.
“The tannins protect protein as it passes through the ruminant, so increasing the amount of protein available to the animal Ð effectively improving its nutritional status,” says Dr Marley. A healthier lamb has better immune protection against parasites Ð and having more available protein will also boost growth rates.

Experimental field trials compared parasite levels in lambs grazing bird’s foot trefoil with those grazing grass and clover swards over a five-week period. The results were impressive, with those grazing bird’s foot trefoil having significantly lower faecal egg counts after just seven days and up until slaughter.

Further trials examined the development and survival of parasite larvae on bird’s foot trefoil and ryegrass. These showed a 31% reduction of Cooperia curticei larvae and at least 58% fewer Teladorsagia circumcincta larvae on trefoil compared to the ryegrass.

However, while the results were conclusive and exciting, the reality of growing birdsfoot trefoil in UK systems was, until recently, prohibitive. However, IBERS has also conducted a number of plant breeding trials in a bid to produce a viable UK variety.

Bird’s foot trefoil has considerable potential as a forage legume, but it is not agronomically well suited to many environments in the UK, according to IBER’s Michael Abberton and Athole Marshall. They are seeking to improve varietal persistence and competitiveness in swards, while retaining optimum tannin levels.

Options include using rhizomes to boost persistence, or developing white clover varieties with profuse flowers, where clover tannins are located. The first of these hybrid clover varieties is now going through National List testing.

Meanwhile senior research scientist Mick Fothergill has been putting some of the new trefoil varieties to the test, focusing particularly on upland areas.

“Bird’s foot trefoil is a desirable species for inclusion in upland swards as it has lower nutritional requirements than traditional pasture forage legumes, and because of its higher tannin content and anthelmintic properties,” he says.

“Previous experiments at upland sites have demonstrated good establishment, but difficulty in maintaining the legume within swards, particularly when grown in combination with white clover.”

However, a recent trial at Bronydd Mawr Upland Research Station using newer UK varieties on less fertile soil yielded some promising results. Sown with meadow fescue at a seed rate of 5kg/ha and 15kg/ha, respectively, the trefoil performed best with a white clover companion, at a low seed rate of 1.5kg/ha.

“We were certainly surprised by the finding, as our previous results led us to expect clover would suppress the lotus,” says Mr Fothergill.

“However, in 2006 the presence of white clover elevated the production of lotus and broad-leaved species, while suppressing the grass component. By 2007 the presence of white clover elevated the contribution of all elements of yield and thus had a highly significant, positive effect on the production of the system.”

During the second year of the experiment the trefoil and clover produced up to 10t DM/ha of high quality herbage from an upland system that had received no fertiliser applications for more than 25 years.

“I revisited the plots this year and could clearly see the Lotus was still dominating the sward and providing a major contribution to the herbage Ð some five years after sowing,” says Mr Fothergill.

“Clearly, given the right conditions Lotus can provide quality herbage in low fertility conditions. We are in the process of producing populations that should provide the basis for new, adapted Lotus varieties.”