January 26, 2009

Drench resistant worms in sheep – other options

Sheep, farming, husbandry, disease, animal health, worms, internal parasites, options to avoid drench, organics, homeopathy, minerals, evaluating products, future developments

By Dr Clive Dalton

When none of these products work any more
- what options do you have?

When drenches fail - what happens

When the day arrives when you find out that the current range of anthelmintics will no longer work on the farm, you will have to sit down and ask where you go from here. The chances are that the consultants and vets you have been using will be as worried as you are.

At present there are the following options:

1. Use 'survival of the fittest'
  • This is survival with a vengeance when you lock the drench gun away. What will happen is unpredictable, as it depends on how big a worm and drench resistance problem you have.
  • Expect poor stock health and performance for some years, but this again will be hard to predict.
  • The biggest worry is how lower fertility and poor growth of young stock will affect the number and quality of flock replacements. You may be forced to buy some in of unknown drench resistance status.
  • Your bank manager may not like this idea, as they hate surprises and unpredictable events.
  • A few farmers have done this because they ran out of drenching options. They say it was very hard in the first couple of years, stopping drenching, ruthlessly culling all daggy sheep and having to breed their own rams. But then things came right fairly quickly after that and they’ve never looked back.

2. Go organic sheep farming

  • Initially this always sounds a great idea when you hear about the premiums for organic meat. But before getting carried away – ask organic sheep farmers about internal parasites and how they manage them as they are a major problem.
  • If officially registered as ‘organic’, (which requires an annual fee) farmers can use their own preparations usually based on cider vinegar, seaweed and the plant wormwood.
  • Organic sheep farmers are allowed to use homeopathy.
  • Plants containing condensed tannins such as plantains are claimed to bring about some control as are the leaves from poplars and willows. Drenching with cold tea has also been used – again for its tannins.
  • When in the opinion of a veterinarian the health and welfare of animals are at risk, then conventional remedies can be used, and indeed they must be used under current law to prevent pain or suffering. All animals treated then lose their organic status and can only regain it after a specified period in quarantine on the farm.

3. Use homeopathy

  • Traditional scientists are highly sceptical and openly critical of homeopathy, because they say it lacks scientific evidence showing statistically significant benefits.
  • Homeopaths say there has been documented research done – but the disagreements between the two sides go on and it looks like a very long war.
  • While this is going on, an increasing number of veterinarians now offer both conventional and homeopathic remedies because they believe many current methods of preventing animal sickness (not improving health as homeopaths point out) with chemicals including anthelmintics are not sustainable.
  • Homeopathy is based on the ancient principle of ‘using like to treat like’ and hence improve the general wellbeing and immune system of the animal so it can control its own health.
  • Homeopathic products need not be registered as ‘animal remedies’ under the Agricultural Compounds and Veterinary Medicines (ACVM) Act 1997 as long as the provider does not ‘make a claim’ as to what the product will specifically cure or prevent.
  • Makers can describe products as ‘promoting general health’ but that’s about all. Users of products can make claims about benefits – but not the manufacturer.
  • There are severe penalties for anyone selling an ‘unlicensed animal remedy’ and a major reason for this is the threat it could be to food safety and our overseas markets.
  • Farmers can either accept what they read and hear about homeopathic products, or do some simple comparisons on their own farm to see if there are benefits.

4. Use mineral & trace element products
  • There is plenty of old peer-reviewed research to show that minerals (especially copper, selenium and zinc) help growth and the development of a young animal’s immune system.
  • Hence there are a number of products on the market, given orally as a drench, or fed as a meal or lick to exploit this.
  • They are sold to promote ‘the general health of sheep‘ and that’s about all the manufacturer can say about them, as they are not registered as ‘animal remedies’ under the NZ Agricultural Compounds & Veterinary Medicines (ACVM) Act 1997.
  • If a product is not registered (showing an ACVM number on the pack), then the manufacture breaks the law if they “make a claim” that the product will do something or the other like kill worms.
  • The makers can only make general statements saying their product assists overall health and boosts natural immunity, but that’s all. It’s similar situation with homeopathic products. The user can make claims as to benefits on their farm, but the manufacturer cannot do this.
  • The products contain minerals and trace elements- and there‘s plenty to choose from. Some include vitamins making the brew even more complex, and farmers assume that if it has all those goodies in it – it’s got to be good. If it smells good (e.g. Cider vinegar) this seems to be attractive.
  • Some farmers add their own extra brews, and there is no law against this if it’s used on their own livestock. It’s not a wise practice and could cause animal health problems and human food safety issues.
  • The big justifiable complaint of farmers is that manufacturers of these products are loath to hand out literature with details of trial results, and they won’t tell you what’s in their brews.
  • There are two reasons for this. First, the makers could not afford to get their products tested by an official research organisation, and secondly, if they said what was it their product, somebody would copy it as they cannot afford the high cost of patents, which are easy to get around in any case.
  • When questioning the use of these products (which is always a good idea), remember that farmers will try new things but if they don’t work they don’t re-order, and may not even pay the bill. So for an honest assessment, check with people who have used anything new for some time (at least 12-18 months) and paid their bills.
  • Key Point: If products truly help to enhance immunity, then that’s all good news. If they allow you to reduce or cut out anthelmintics – then that’s an added bonus, which also helps immunity. So then it will be much easier to identify highly immune sheep to improve the accuracy of selection.

Evaluating products on your farm
In these days where so much independent research done by old government departments of agriculutre has been killed off, you have to be very careful accepting research results done by commercial companies who also sell the product they are testing! So it’s tempting for farmers to test thing on their own farm.

This is not easy and all that is ever achievable are very basic comparisons, provided you pay attention to some important points:
  • Realise that anyone with a formal scientific training will rarely accept your results. If you find major benefits – somebody will always say that it was a fluke and that you probably even ‘cooked the books’! Ignore them as the objective is to convince yourself.
  • You must have an untreated ‘control’ group that are similar in age, sex, weight and background to the treated group or groups. Indeed the control group is the most important one!
  • Aim for at least 25 animals per group – the more the better as animals disappear on farms!
  • Manage all the groups in a similar way – and run them together if possible.
  • If you need to run a group separately (e.g. to avoid cross contamination), then ensure they have similar grazing and management.
  • Before you start – discard from the total group any animals that look sick or are very large or very small. You need to get your trial sheep from an even line to start with.
  • Then randomise them into their trial groups. Simply draft them off in turn through the race for each treatment group.
  • Look them over after drafting to check there are no ‘odd-ball’ animals in any group. Discard these and replace them with animals picked at random again from the main mob.
  • Make sure all sheep are well identified by groups – a good long-lasting raddle mark may suffice. Individual ID using tags is nice but it may not be necessary.
  • Make sure their ID will last till long after the trial has finished as you’ll be amazed at how interesting these sheep may become later. And in any case you may not see benefits for a long time.
  • Data recorded could be things like live weight and FEC/FCS at the start and end of the comparison. Don’t get bogged down recording too much – only essentials that you need to make a decision. Keep it simple.
  • Record the information in a hard-backed exercise book and not on separate sheets of paper that will get lost. Don’t worry about the book getting covered in sheep muck – it’s a working document!
  • If you don’t get at least a 10% difference between any treated groups and the control – be wary of drawing any conclusions. Assume there are no differences – which is a very important conclusion indeed! This will certainly save you money from buying things that don’t work.
  • Be wary of seeing things through rose-tinted spectacles as the mind can play tricks and confirm what you want to happen. Remember this is what a myth is.
  • If you want to assess visual differences between groups – then get someone from outside who has never seen the sheep before to do the job and don’t tell them which group is which.
  • Remember – the aim is to avoid fooling yourself by spending money on products that don’t work.
Promised future developments
There are certainly plenty of things talked about and being researched, but it depends how long you are prepared to wait. When you hear researchers interviewed and read reports of their predicted delivery times – it seems we only have to wait for 2-5 years and at most a decade.

But because of the stop-start way research is funded these days and the bureaucratic and commercial restrictions on getting results out to farmers at a sensible cost, don’t hold your breath! The average sheep farmer at age 50+ will probably never see most of these.

But with a positive outlook - here’s the current wish list:
  • New drench chemicals.
  • Biological anthelmintics that interfere with normal worm metabolism.
  • A pasture L3 larvae test to locate high contamination areas to avoid when planning grazing.
  • Plants with condensed tannins such as Lotus or plantains.
  • Vaccines to enhance the animal’s own immunity. This is the Holy Grail of parasite control!
  • Fungi that kill worm larvae on pasture or in the soil.
  • Genetic markers (called Marker Assisted Selection of MSA) using DNA profiling to find sheep resistant to worms.
Disclaimer This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.

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