Diet may hold key to less dependence on wormers
Diet may hold key to less dependence on wormers
Increasing protein in ewe
and lambs rations may hold
the key to reducing use of
wormers and risk of resistance.
Emma Penny reports
WITH wormer resistance widespread in the southern hemisphere, and rising concern in the UK, extending the life of available and effective wormers is vital.
So says SAC research scientist Lewis Kahn, who, with colleague Ilias Kyriazakis, is involved in an EU-wide project investigating alternative control strategies.
"Scientists and producers must act now to minimise further development of resistance. We need to reduce our dependence on anthelmintic products to extend their effective life."
Reducing dependence will mean adopting a number of strategies: Better grazing management, selecting animals with better resistance to worms and improved nutrition.
Nutrition is under scrutiny at SACs Bush Estate and the Moredun Research Institute, Edinburgh, explains Dr Kahn.
"We are looking at the relationship between protein supply and resistance to worms in growing lambs and pregnant ewes. It could be that feeding extra protein enhances immunity to worms, reducing requirement for wormer, and consequently risk of resistance developing."
Immunity to worm infection is at its lowest when protein requirements are at their highest, he says. "Growing lambs and ewes in the last stages of pregnancy and early lactation are most at risk."
Growing lambs have a high requirement for metabolisable protein. Rations high in protein are required so that lambs can continue to grow even if they are parasitised, he says. "Once lambs are through that particularly vulnerable stage, and have developed immunity to worms, they can ingest parasites but the body suppresses them, so they have little effect on production."
Work at SAC is comparing high and low protein diets to see whether this affects immunity to worms and growth rate. The trial, which started in June, will run through to early December.
Black scour worm
"We infected lambs with black scour worm – a type of roundworm – at nine weeks old. Lambs are in pens to ensure all environmental factors are the same, but their diet is being adjusted to reflect what would happen at grass."
While all rations are based on a moderate ME level, lambs on the low protein diet receive 9% crude protein on a DM basis, while a 16.5% protein ration is being fed to those on the high protein diet.
During the trial, diets will be switched in an attempt to examine the effects of changing protein supply on immunity to worms.
Dr Kahn is waiting for statistical analysis of the first results, but he already has an idea of the outcome of the first part of the trial.
"So far, it appears that diet has little effect on growth rate in the first five weeks after infection. This was to be expected, as worms have their major effect after this. "But I expect differences to become more apparent as the trial continues – those on the high protein ration should be more resistant to worms, and so should have higher growth rates. But it is too early to draw firm conclusions."
Next spring, the project will also begin to look at the effect of protein supply to pregnant and lactating ewes. These animals suffer a breakdown in immunity to worms at this time, increasing pasture contamination.
"Protein requirements for the ewe in late pregnancy and early lactation are high – by week four of lactation they increase by about 250% compared with usual demands. We hope that by giving more protein to pregnant and lactating ewes, the breakdown in immunity will be avoided, and that this will stop the ewe dirtying pasture, which again increases worm challenge to lambs.
"Giving additional protein to ewes may be a more cost-effective way of reducing pasture worm burdens and requirement for wormer than feeding high protein rations to lambs," he adds. *
Immunity to worm infection is at its lowest when feed protein requirements are at their highest, says SACs Lewis Kahn. Growing lambs are most at risk of infection.
RESEARCH PROGRAMME
• EU project, EC funded.
• Effect of protein on lambs.
• Ewes also in trials.
By week four of lactation a ewes protein requirements increase by about 250% compared with usual demands. Feeding additional protein may be one way of reducing pasture worm burdens.
EU takes environmental approach
Other EU states are also involved in the trial to develop environmentally friendly approaches to worm control in sheep and goats, reducing reliance on anthelmintics.
In France, researchers at INRA, the state funded research and advisory body, are looking at worm control in goats, explains Dr Kahn. "French producers want to maintain the high quality image of goats cheese, while consumers are calling for farmers to use more pasture without an increase in the use of wormers.
"That will lead to greater parasite challenge. Goats dont develop the high levels of immunity seen in sheep, so they are always susceptible to worms. Research is again concentrating on nutrition, particularly the role of sulphur amino acids such as methionine."
Spain and Greece are also involved in the 1m ecu (£670,000) project. Both countries have previously relied on dryland grazing for sheep, but an increase in use of alternative systems based on irrigation and cultivated pasture has led to a rise in worm concerns.
"Both countries are looking at the effect of increasing intensity on production and prevalence of worms."