De-worming the sensitive horse

De-worming the sensitive horse

Most horses find the taste of anti-endoparasitic pastes or de-wormers - which are often administered by oral syringe - pretty disgusting and will do everything possible to avoid it. They find it aversive. Evasive tactics your horse may employ include raising their heads out of your reach, attempts to move away or even bolt. Some, when restrained, may even try to bite or kick you when they find there is no escape. De-worming can not only be very tricky, but dangerous too!

Even when you do manage to squirt that paste into the back of the mouth, many horses will attempt to spit it out again. In the past, I have tried to follow this up quickly by offering them some really tasty food or treats to encourage them to swallow. However, like many owners I come across, the taste may be so aversive that they are suspicious or not interested in food or their sense of taste may even become temporarily tainted. Some pastes try to compensate for this by adding a flavour, such as apple. Whereas I have had some horses find this not quite so aversive, there are plenty out there who still do.

Even if we do manage to restrain the horse with headcollars, ropes and chains and additional helpers and manage to keep their heads up afterwards long enough for them to swallow, this just makes the event even more aversive to the horse. The more aversive something is, the more likely the horse is to remember that event and all the environmental clues or cues that predict it meaning that, next time, you may have even more of a fight on your hands.

The question is, do you escalate the pressure, number of people required to hold the horse down, the ropes and chains? If you do, then your horse may eventually give in. If he does, he is certain to associate you with this significantly aversive event and you may find his behaviour towards you deteriorates in other scenarios too. If your horse doesn’t give in, his behaviour may well get worse – even dangerous.

Even so, de-worming our horses is such an important part of equine management. A large endoparasite or worm burden can cause loss of condition, anaemia, diarrhoea, colic and even death. Although it is recommended that we do not overdo de-worming of our horses, with many now undertaking faecal worm counts as part of endoparasite control, most horses will inevitably need to be treated for worm infestations at some point. So not treating your horse is not an option for most.

So what do you do about it?

The best case scenario is that your horse would have been counter-conditioned to being de-wormed using an oral paste from a very young age. Counter-conditioning is where something aversive is paired with something which is very pleasing and rewarding – or an appetitive. The appetitive must be more rewarding to the horse than the aversive is noxious. This means, in simple terms, that you need to start with very small amounts of the aversive and a lot more of the appetitive.
However, not many horses have been started up to a de-worming programme in this way and so most of us are already faced with a horse that has learned the syringe full of the treatment is very unpleasant indeed.

This means that we need also to desensitise the horse to all the environmental cues that predict the unpleasant thing is about to happen as well as then counter-conditioning them to the unpleasant taste of the treatment itself. This needs to be done slowly over a period of time and without overdoing each session. For some horses, it may also be the sensation of having something squirted into their mouth that requires additional counter-conditioning.

The horse pictured above has had some previous clicker training – where a unique sound such as a click or a whistle is paired with a reward such as a horse treat or piece of apple. The unique sound or click predicts that a reward is coming and, once appropriately paired with the reward, the click itself becomes a ‘yes’ or bridging signal telling the horse that the behaviour performed at that exact moment when the click was heard is what earned him the reward. Getting this connection solid before you try to begin changing or teaching a behaviour is so important, as is making sure you only mark and reward calm behaviour. Otherwise, you can get an over-excited or ‘muggy’ horse. It is advisable to get an expert to start you off on the right track with this.

This particular horse did have an aversion to the worming treatment although his owner had done some ‘desensitisation’ work with him previously to get him to associate an empty syringe with good things. This has been followed by a small amount of water being squirted gently into his mouth, then marking and rewarding when he swallowed. However, the pictures below were taken after three short sessions of around 2-3 minutes each on the same day with the real thing.

You can see that in the main picture, I am presenting the syringe of de-worming treatment with the cap off, so he can really smell the paste. He is not too sure to start with. However, each time he takes a step or moves his head closer to the syringe, I mark that improvement in behaviour with a verbal tongue ‘click’ followed by a reward. I am asking him to ‘target’ the syringe to the corner of his mouth. By marking each incremental step towards this goal behaviour and rewarding each ‘click’, I soon get him voluntarily putting the syringe in his own mouth. When he does this, and remember, he can taste the medicine but I have not injected it into his mouth yet, he gets a jackpot reward and we finish the session.

After a few more sessions like this – to get the behaviour solid – we will be able to inject the paste and he will then get an even better jackpot. If we have done it without raising his anxiety levels, he will then choose to take the paste next time, because in accepting something that is a little unpleasant, this actually gets him something that is far more pleasant and rewarding in the end.

I should point out that this horse is in his own paddock that he has pleasant associations with and is without a headcollar and free to move off any time he wants to and so has complete choice as to whether he stays for the treatment or not. This is an important part of the process and helps to keep anxiety levels low. I also do not move the syringe towards him, but present it so that he can move himself towards it. He practically de-worms himself!

© Nicola Chamberlain. April 2014