New Zealand Sheep Husbandry - Using Refugia to control worms

By Dr Clive Dalton

Refugia – what’s it all about?
The word ‘refugia’ seemed to appear out of the blue about 5-6 years ago, and was used by veterinarians and parasitologists when talking to farmers about worms (internal parasites) in sheep and in cattle.

Finding out about the bad news

• In a survey of sheep and beef farms by Meat & Wool around 2006, it was discovered that worms had become resistant to a range of anthelmintic drenches, and that some urgent action was needed to stop the rot!
• A massive bureaucratic panic resulted with one of the main results being the formation of a programme called ‘Wormwise’ to advise farmers what to do to control worms, and especially how to stop drench resistance increasing.
• Wormwise is still in existence, but with much less panic now as despite dire predictions that no new drenches were in the pipeline, at least two are now on the market which are promoted as solving the resistance problem.

We should have known!

• Drench resistance in worms should not have come as a surprise, as a few lone voices about 30 years ago warned this could happen if we became totally reliant on the new drugs (at that time) to kill worms.
• The worms would outsmart the humans through the simple process of ‘the survival of the fittest’, so that those that became resistant to these chemicals would survive and multiply.
• But then of course – nobody wanted to think too far ahead and about the downside of using chemicals to kill worms, as everybody involved was making money from their widespread use – the big international pharmaceutical companies who made them, the vets and distributors who sold them, and the farmers who used them.
• It was easy (too easy) to believe that predicted problems were only conjecture. It only took 30 -40 years to prove it was fact!

Refugia arose from the insect world

• It was when parasitologists started to describe how worms started to develop resistance that the word refugia appeared, as similar concerns were expressed about insects about 40 years ago when chemicals like DDT were used extensively to kill them. It was a particular concern with mosquitoes in Africa.
• It was predicted and proven true that a population of insects resistant to chemicals could keep on increasing, and one way to stop this was to have a ‘refuge’ where ‘susceptible’ insects could survive (by not spraying) to mate with the resistant ones and thus slow the rate of total resistance in the population.
• Exactly the same situation was described by parasitologists as a possible way to slow up the rate of drench resistance happening in worms in sheep and cattle.

Refugia was a concept
Refugia was and still is a concept – and is by no means a proven solution. It was the only good news that parasitologists could come up with at the time, and it sounded reassuring – to some.

How is refugia supposed to delay drench resistance in worms?

• In the worm life cycle, male and female worms mate in the gut and produce eggs, which go out in the faeces on to the pasture where they live as larvae, then crawl up the grass again and be eaten by the host for the cycle to continue.
• Anthelmintic drenches kill all the worms (some kill the eggs too) that are susceptible to the particular chemical, so they can’t mate and lay eggs.
• So when resistant males mate with resistant female worms, their offspring are not killed and they produce resistant offspring.
• To slow up all worms becoming resistant, we need drench resistant worms to mate with susceptible worms, so a proportion (unknown) of their offspring will be killed by drenching.
• So the more susceptible worms that are in a ‘refugia population’ on the farm, the slower will be the rate of descent toward total drench resistance.

How to keep a refugia population of worms?

• This done by not drenching all the animals in the mob – which used to be best practice before drench resistance was identified.
• Best practice now is to leave ‘a proportion’ of the mob undrenched.
• The size of this proportion is not easy to define – figures like 5, 10, or 15% are suggested, or you should not drench the biggest animals in the mob that are thriving.
• These will be the refuge for worms susceptible to drench chemicals – so will hopefully delay the time when all worms are resistant to chemicals.

Will refugia work?

• Some sheep trials have been done in sheep and showed that drench resistance was slowed up.
• But other sheep work in Australia showed that refugia will only delay the evolution of drench resistance where a large proportion of the worm population escapes exposure to drench chemicals.
• The key thing is that the idea of having a population of worms in a flock susceptible to drench chemicals is a concept which seems to be common sense too.
• It’s simply to avoid as much ‘chemotherapy’ to kill worms as much as possible to delay the day when all worms are genetically resistant.

What’s good for refugia?

• Drench on the basis of a Faecal Egg Count (FEC) and veterinary advice, and not by the calendar.
• Reduce the number of drenches given.
• Extend the intervals between drenches.
• Leave a proportion (5-15%) of the top animals undrenched.
• Concentrate on drenching the poorer-performing animals in the mob.
• Don’t drench mature animals, as their immune system should protect them from worms.

What’s bad for refugia?

• Drenching thinking that this will kill the worm larvae on the pasture. This is a myth.
• Using only one class of stock on an area – you need to mix the species grazing to act as vacuum cleaners for the worms that affect other classes of stock.
• Note sheep and goats share the same species of worms.
• Drenching young animals and then putting them on to clean pasture. This will definitely allow the drench resistant larvae to multiply and when they get back inside the host, to meet other drench resistant worms to keep on multiplying and increasing drench resistance in the flock or herd.

How can you find out if there are drench resistant worms on your farm?

1. Realise that there are many different species of worms, and nto all of them may be resistant to the drenches being used at any one time.
2. Also remember that over 90% of them are in the form of larvae on the paddock and not inside the animal.
3. The test for drench reistance is called a 'Faecal Egg Count Reduction Test' or FECRT/
4. You have to identify a sample of individual animals, then do a FEC to find out their worm burden before drenching them with the particular drench family to be tested.
5. The you do an FEC again, and if the product under test was fully effective, then it should have killed at least 95% of the worms.
6. See your veterinarian for full details of the protocol needed and the costs.

The new drenches

• The two new families of drench chemicals which have appeared on the market work in a different way, and it is stressed that they will kill any worms that have developed resistance to the previous chemicals.
• But parasitologists are warning that care needs to be taken with their use, otherwise we will go down the same track and produce the same resistance problems that has happened before.

New Zealand Sheep - Facial Eczema damaged liver

By Dr Clive Dalton

The fungus Pithoymyces chartarum is found in pastures mainly in the Northern parts of New Zealand, and in autumn after a summer dry period when a lot of dead litter has accumulated in the pasture base, rain and dew can provide ideal conditions for the fungus to produce spores in large numbers. But the spores can also be found in large numbers on new short fresh autumn grass.

The fungal spores, especially the freshly-grown ones produce a toxin called sporidesmin, which causes thickening of the bile duct and may even cause its complete blockage.

Sheep gall bladder punctured to show bile and healthy
bile duct entering the liver tissue

A damaged liver cannot get rid of waste products, and a breakdown product of chlorophyll accumulates in the tissues causing jaundice and sensitivity to sunlight.

Sunlight very quickly causes swelling and severe inflammation on exposed white skin parts of the body.

There can be some repair of the liver, but it depends very much on the level of damage. In a recovered liver you will see knew small lobes that have grown.

Sheep's liver cut through centre

The liver pictured above is from a 6-year-old ¾ Romney ewe with ¼ Finn. She spent 5 years of her life on a farm that is very prone to FE, so there’s little doubt that she will have experienced a toxin challenge and liver damage during those years. She has reared twins most years in her life and it’s amazing that she was able to do this.

In the picture at the knife point is a little motley yellowish tissue on the surface of the liver which shows toxin damage. A real badly damaged liver is like a lump of wood.

But note especially the nice new healthy liver lobe on the right of the picture, and the 3 new small ones at the top right, and how healthy the internal tissue is.

For the last two seasons, this old ewe has been treated regularly with a zinc-based nutritional supplement which has protected her from further liver damage by toxins, and helped to stimulate new healthy liver growth.

Internal signs of a dysfunctional liver
Often at post mortem of a ewe dying close to lambing, you'll find two dead almost mummified lambs insider her but great masses of fat in the body cavity which the liver has not been able to process to nurture the lambs.

Sheep husbandry - Castrating lambs with rubber rings

By Dr Clive Dalton

Castrating lambs with rubber rings
Using rubber rings is the best way to castrate lambs in both large and small flocks. It is bloodless and research has shown that the intense pain only lasts a short time. Lambs should be castrated using rings before they are 6 weeks old - the younger the better.

The main concern is to make sure the ring is placed in the correct position, so the ram will become a proper wether.

If the testicles are missed, then the lamb will be a 'cryptorchid' where one or both testicles can be felt under the skin along the belly, or squeezed back up into the body cavity. These sheep are usually infertile, but there is always the risk of an odd animal being an effective ram.

Cryptorchids grow faster than wethers due to the testosterone produced by the testicles.

Objective
The procedure must be done so that the scrotum, along with both testicles, is captured when the ring is released. The ring must be above scrotum and testicles, and below the rudimentary teats.

Method

1. Get an assistant to catch the lamb and sit it on its rear end on a board or rail at standing height.



2. Grab the end of the scrotum and pull it through the open ring.



3. With the ring fully open and resting on the lamb's body, use your fingers and thumb to locate the testicles and press down to squeeze them through the ring. Hold them there and release the ring.


4. Before flicking the pliers off the ring, make sure there are two testicles now in the scrotum.


5. Double check - testicles in - teats out!

Sheep husbandry - docking lambs' tails

By Dr Clive Dalton


Docking lambs' tails
Removing lambs' tails has been a standard part of sheep husbandry from early times, mainly to prevent the formation of soiled wool or 'dags' sticking to the wool of sheep eating lush pasture. Removing soiled wool or dagging has always been one of the least popular jobs on a sheep farm.

Hill and mountain sheep in Britain for example, and sheep in dry desert areas do not need docking, as their normal diet is made up of dry herbage which does not produce soft faeces which then stick to the wool around the britch.

The other important reason for not docking hill and mountain sheep breeds in cold climates is that the tail protects the udder and rear end and is a said to be a source of fat which the sheep can use in times of poor nutrition.

It is done for these reasons:

• First to prevent blowflies laying their eggs among the dung and the maggots hatching out and eating into the sheep's flesh. In the worst cases flyblown sheep can die very quickly.
• Lambs sucking daggy ewes get dung on their heads and this makes them prone to blowfly attack.
  
• To prevent the soiled wool from contaminating the clean wool of the sheep with green dung stain which then costs money to scour out.
• The NZ Shearer's Union requires all sheep put up for shearing to have been dagged. This is to prevent shearers picking up bacterial diseases such as campylobacter and salmonella from the dung.
• For cosmetic reasons - there's nothing worse than looking at a flock of sheep with rear ends caked with dags.

Consumer concerns
An ever increasing number of people these days think food comes from supermarkets. They have no reason to believe anything else, as they are totally ignorant of what goes on in the production end of the agricultural or horticulture industry.

But they are concerned about animal welfare issues, which they learn about via television - usually when there is a crisis which has good media attraction. The docking of lambs' tails is one of those issues, highlighted by an inquiry I had from a researcher at a major UK supermarket chain, about the tails of New Zealand lambs being too short and causing concern.

NZ Code of Welfare:

Fortunately in New Zealand we’re well covered in the new Animal Welfare (Painful Husbandry Procedures) Code of Welfare 2005 as part of the Animal Welfare Act 1999. Here’s some key points from it.

Minimum Standard No. 4 – Tail docking of sheep

(a) Tail docking of sheep must only be undertaken where there is significant risk of faecal and urine contamination, and/or flystrike, that leads to poor hygiene, health and welfare and/or failing to do so adds a significant cost to the system.

(b) While complying with Minimum Standard 2(a), tail docking without pain relief must be performed when sheep are as young as possible, and not greater than six months of age.

(c). When tail docking a sheep over the age of six months, pain relief must be used.

Minimum Standard 2a says that:

‘Painful procedures must not be performed on newborn animals less than 12 hours old where handling, pain and post-operative complications are likely to compromise survival through impairing maternal bonding and/or colostrum intake.’

Minimum Standards will stand up in a court of law but the Codes also have ‘Recommended Best Practice’ which do not have the legal power of a Minimum Standard. But they are meant to be followed as part of ‘Best Practice’.

Recommended Minimum Standard

For tail docking of lambs, the Recommended Minimum Standard says that ‘when sheep are tail docked, their tails (excluding any wool) should be left long enough to cover the vulva in females and at a similar length in males.’

Why Kiwis dock too short?

If you have ever been in a docking gang on a big farm, you know why. When lambs are coming at you at great speed, you have to hit the right spot on the tail with the hot cauterising iron or the ring pliers without delay. You are not allowed much time to decide which is the correct spot. The greater concern is that you may leave the tail too long, (which will upset shearers later on), rather than dock the lamb too short.

Consumers's concerns must be recognised

But from now on ‘getting it right’ has become an important priority from what folk are thinking and clearly dictating as they push their trolleys around the supermarkets of the world.

It’s no good us thinking shoppers don’t know anything about sheep farming. They don’t. But this is no reason to ignore the messages about buying lamb they are sending via the supermarket checkout.

Stud breeders

These in my view are the worst offenders at docking too short, as it seems that a very short dock, or none at all does a better job of showing off a ram’s meaty rear end.

Damage caused by short docking

Short docking damages the tissues around the anus and can affect the sheep’s ability to defaecate properly hence causing more dags. A lambs tail needs to be long enough to wag!

Lamb tail docks
In your photos you can clearly see the caudal folds with ligaments that run alongside the anus and under the rectum, so when the tail is lifted the rectum is lifted and poo (even runny poo) is directed away from the body. Short tails can't do that and the poo slitters down the back end.

What is the correct length?

Tail ring in correct position on female lamb's tail.
The dock should be long enough to cover the vulva.

Tail ring in correct position on male lamb's tail.
It dock should be a similar length as in the female.

Sheep Husbandry - blade shearing method

By Dr Clive Dalton
(Photos by Des Williams)

Shearing a sheep using hand shears.
A blade shearing method.

There are may methods used around the world to shear a sheep using hand shears or blades.

The method shown below is used in the north of England and in Scotland. In parts of Wales the sheep have three legs tied together, and are shorn on a long stool with the shearer sitting on one end.

In New Zealand Merino sheep in the high country are still blade shorn when shorn in winter or pre-lambing to leave more wool on them to protect them from cold weather. To achieve the same result with a shearing machine, combs (called 'snow combs) are used with deeper teeth.

Step 1
Sit the sheep on its rear end in a comfortable position . Keep your toes well in below the sheep with its body leaning against your legs. The sheep will initially slump into a concave position.



Step 2
Take hold of the sheep's ear in your left hand (right handed shearer) and start shearing down the side of it's face, around the back of the head past the mid line, and shear the wool down towards the brisket to open the fleece out.

Step 3
Start shearing down along the back of the neck and keep coming around to the front leg. Notice in the picture how the sheep is now pushed out away from the shearer with the knees.


Step 4
Lift up the front leg and shear along it. Then holding the front leg, continue shearing down the side.


Step 5.
Continue shearing starting near the backbone and then come right around to include the belly.
Go as far across the belly as you can. In males watch out for the sheep's prepuce, and in rams their penis which may protrude with the pressure on the belly.



Step 6
In females, take care not to cut the udder or teats. In young females (hoggets) put your fingers over the small teats to protect them when shearing near them towards the bottom of the belly.




Step 7
Now the job gets easier as you can lay the sheep down. This is especially useful with very large sheep such as rams.

Note that the sheep is kept down, and is lying very comfortably, by kneeling on the neck wool, which is unshorn on the other side of the sheep.

Then you can concentrate on shearing along the length of the sheep, making sure you first shear well over the shoulders, and then along the back.

Note my left hand being used to steady the sheep if she starts to kick. Press down and she'll soon lie quietly.


Step 8
Now change from kneeling on the neck wool to putting your knee right across the sheep's neck. The sheep now cannot move, and allows you to easily reach the rear end of the sheep.


Step 9
In this position, resting on your right knee and with your left foot in the sheep's crutch, it's easy to shear around the tail and the crutch.


Step 10
Now you need to shear as far over the tail as you can reach, as this is where the sheep is going to sit when you sit her up to do the last side. First loosen the wool so it's standing upright and easy to cut. If the sheep is lying on that bit of wool, it's hard to shear with the blades.

To raise the sheep up, pull it over by some skin around its tail dock. This is much easier with UK hill sheep which have long tails - and which have to be shorn by going down one side and up the other.



Step 11
You now want to get the sheep from lying on its side to sitting on its read end again - like when you started. There's a tricky move (shown in the picture) by grabbing a front leg to pull it up from where you ended - but just get it back up as easy as you can.


Step 12
Here you can see I am back on one knee with the sheep held by the nose and its head resting on my other knee. Then start shearing from the brisket up to the nose to start the last side.



Step 13
Continue to open up the neck and down to other front leg.


Step 14
You can keep on shearing while kneeling, but it's much easier to lay the sheep down and hold it there with your knee over its neck. You can then shear from the rear end (which you shore when you did the first side), right up to the neck.




Step 15
Preparing the fleece. Lay the wool out for 'skirting' which is where you remove the belly wool and all the stained and coloured pieces around the edge, short bits of wool and any wool with raddle or plant contamination. The aim is to keep the main 'body wool' with similar length staples in one lot to be marketed.





Step 16
Rolling up the fleece. There's no need to do this in New Zealand but it's used in UK, and is a handy trick to carry a single fleece. Lay the fleece out and fold in both sides. In UK the hill breeds are wrapped with the skin side in, and lowland breeds are folded with the skin side out.

Once the sides are folded in - start rolling the fleece from the tail end. If confused over which end is which after the wool is off - look for the neck wood which is usually shorter and finer.


Step 17
When you get near the neck, start pulling some wool and twisting it into a band.


Step 18
You end up with the fleece wrapped up for easy carrying without it falling apart. In New Zealand, fleeces are put loose into the fadge.

'Wormwise' - Time to move on

By Dr Clive Dalton

Launch
'Wormwise' was formed to come up with a 'National Strategy' to combat the rising resistance of internal parasites in sheep and cattle to the chemicals used in drenches to kill them. It's launch in 2006 was sponsored by Meat & Wool NZ, the NZ Veterinary Association, the Ministry of Agriculture and Forestry and Agcarm. It is still in business with the same objectives, but its work and promotion seems to have gone quiet.

Getting the message out


The Wormwise message was spread by farmer meetings, field days and a seasonal newsletter with Number 1 in May 2006, and the last one I have is Number 9 in September 2009. Wormwise also appointed a national manager (a veterinarian) to keep up the momentum and motivate farmers into action. There have now been two of these.

What's gone wrong?
There's now big concern that the 'national worm management strategy' may have run out of gas, while the problem certainly has not gone away. I believe the programme has done well to last this long, and the organisers should not be surprised at its current status if they looked at what happened to the many other national farming campaigns.

Campaign stages
In my MAF days I worked on many campaigns that went for a while then tailed off, no matter how much money or resources were thrown at them. There were always these well-recognised stages, listed in rough order of priority:

• Identify a problem. Report and publicise it as a 'crisis'.
  
• Brief the Minister to get political traction, and make sure he gets political kudos from it.
• Get boffins to push the campaign stressing that ‘this has got to be good for farmers’.
• Use panic to get the attention of farmers via the media who are always hungry for 'news', especially if it's new and generally bad.
  
• Keep the panic going to extract a budget from the bean counters, and keep complaining (through the media) that it’s never enough, and if you don't get more, an even greater disaster will hit the industry.
• Prepare an information ‘package’ and a ‘campaign’. Hire costly PR help, or build your own communications team with a ‘champion’ for the programme.
• Organise 'delivery of the programme' with publications, press releases, newsletters, videos, print and TV adverts, field days and seminars.
• Have media-trained 'experts' in your team available for interview at all times.
• Always have a press package available.
• Nowadays, set up a website - and forget to keep updating it or run out of ideas over what to put on it. Keep repeating the same old message.
  
• Keep informing the knowledgeable, and preaching to the converted.
  

Initial flush of success
Things go well for the first 18–24 months, and then they start to go flat. It’s like a slow puncture, which you try to ignore hoping it will stabilise, and you won’t have to buy a new tube or worse still a tyre.

Failing the basic marketing test
We boffins regularly failed the basic test of marketing - ‘to wear your clients’ boots’ and we forgot that farmers had a million other things to worry about as well as what we were pushing at them.
We remembered the boot's advice at the beginning, but forget to keep running the check as things tailed off to see what was changing. We failed to see things were changing all the time.

Blame the innocent
We also operated the great ‘Yes Minister’ advice from Sir Humphrey, of never taking the blame for failure, and always blame the electorate. In our case it was farmers who didn’t take up our brilliant ideas, didn’t come to field days and didn’t read our literature. They couldn't see what was good for them! It was their entire fault and never ours.

Looking back now, I’m not proud of the opportunities we botched through running around like headless chooks, and missing the obvious signs of where the wheels were getting loose.

Why Wormwise has done its time and should RIP:
Here's my thoughts:

• Killing the wool levy and the new drenches on the market are not the main reasons.
• The campaign always had too much veterinary input, and not enough farmer psychology.
  
• Farm owners (average age around 60) quickly got weary of being earbashed about the impending disaster, and their failure to act. Humans get sick of this after a while, especially when disaster doesn't arrive.
  
• The main Wormwise message to find out where your sheep were in terms of drench resistance seemed great, but unless farmers had big death rates, it was one of those things that could be left ‘till the first wet day’.
• Most farmers genuinely believed that they didn’t have a drench resistance problem - again as death rates were not high, and worms were not an obvious problem.
  
• When asked about the drenches used, most farmers said that their current drenches ‘seemed to be working OK’.
• Farmers accepted dagging and drenching, and then more dagging and drenching as normal routine. Things had to get very bad to get some veterinary involvement.
  
• Farmers realised that a full Faecal Egg Count Reduction Test (FECRT) took a lot of work, and cost a lot more than expected. Vets didn’t feature this - obviously.
• Many farmers simply didn’t want to know. It was like being told to have a health check. Farmers in the last 10 years have had other things to worry about like finding ways to stay viable and reduce work as staff became harder to find.
• Farmers can be easily convinced that their stock need a drench, and few base this on a FEC. If in doubt they drench, and at least they feel better afterwards and the dogs have enjoyed their run!
  
• Farmers are starting to understand the ‘Refugia’ concept of not drenching big healthy-looking individuals in a mob. They like it as it saves drench!
• The advertising for the new drenches reassured farmers that if they did have major problems with resistance, these products (which were expensive) would save them quickly.
• Repeating a known message soon gets boring as farmers know what it is, so ignore the repeats and switch off.
  

The future for worm resistance
Drenching based on ‘chemotherapy’ was never sustainable in the past, although we thought it was. It cannot be part of a future New Zealand which is clean and green, and a low-chemical animal protein export business. Evolution being what it is, the more drugs we hit parasites with, the more they will use genetics to get around their problem. We must use the same weapons.

Sadly the large international pharmaceutical companies who manufacture anthelmintic drenches don't see it this way in marketing their products. So large animal vets are in a quandary as they depend on drench sales for a large part of their income, while on the other hand trying to carry out the Wormwise principle of reducing the overall rate of anthelmintics.

The drench business is very competitive with few products being sold as 'vet only'. So this results in a massive adverting push in all the media, especially on TV during rugby events. The list of promotional giveaways used to be limited to domestic products and clothing, but now it has moved to electronic equipment.

Reduce chemotherapy


More and more chemotherapy is not the answer - genetics is, but this message has problems as it is mentioned, almost as a last resort in the Wormwise programme. New Zealand trained veterinarians are not strong on genetics, and in any case, using genetics doesn't earn them much money, other than from Faecal Egg Counts which farmers can do themselves now.

Plenty of evidence that genetics is working
We now know that sheep can be bred that can handle worms, to cut the costs of dagging and drenching (in that order). It’s simply a repeat of how sheep breeders fixed Facial Eczema using the survival of the fittest, and with modern technology, progress could be very much quicker.

There are now plenty of breeders who have been working away unrecognised for years, and now have a genetic solution. This is measured in many ways but the simplest one is how few drenches they need to give to their lambs and hoggets. Their mature ewes have never been drenched for years.

Change when profits decline more
Sadly genetics won’t get traction unless sheep profits decline further, and farmers realise how much they are spending on animal health (mainly drench). Also that farm labour dries up as young folk realise there's an easier way to make a living than hauling around today's 80-100kg ewes to take dung off their rear ends.

It's not worth Wormwise getting upset at farmers' complacency over the national strategy. Somebody needs to talk to farmers and get their views about how they want to manage internal parasites, and not fall into the age old trap of boffins preaching that 'this has got to be good for them'.

And it would be a good idea to get more lectures on animal breeding and genetics into vet training.