CHOKE - Hoofbeats

Biting off more than you can chew

CHOKE Having fed the horses you are enjoying a few moments in the stable just listening to the sounds of contentment as they eat, and breathing in the wonderful aroma of horses.

The peace is interrupted by coughing.

With your ‘something’s not right’ antenna suddenly alert, you check to find one horse struggling to breathe and swallow, its neck stretched out while food and liquid are emerging from the nostrils.

You have never seen it before but you recognise Choke, so what can you do for your horse?

Dr Jennifer Stewart BVSc BSc PhD Equine veterinarian, CEO Jenquine and consultant nutritionist.

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hoke is a serious, painful crisis for horses that can last several hours or even days - but is not usually a life-threatening one if it is treated and resolved early. It is quite a common veterinary emergency with potentially serious consequences including pneumonia, scarring and rupture of the oesophagus and occurs when food or a foreign object blocks the horse’s oesophagus. The blockage may be partial or complete, and choke can occur as a single episode or it can be a chronic, recurring intermittent problem.

Unlike ‘choke’ in humans - which is an obstruction of the windpipe choke in horses is an obstruction of the oesophagus – the tube that carries food from the mouth down to the stomach. It involves food or other material becoming stuck anywhere between the back of the throat and the entrance to the stomach in the abdominal cavity (Figure 1).

Choke is a relatively common condition that occurs when food or a foreign body blocks the horse’s oesophagus (gullet), which is the tube that takes food from the back of the mouth (pharynx) to the stomach.

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WHY CHOKE Choke can happen when horses eat hay or straw, hard treats, carrots, high fibre ‘treats’ or non-food objects such as wood, bits of rope and even riding crops! It’s clear that large, odd-shaped and bulky things won’t make it down a horse’s oesophagus - but why do horses choke on feed?

Generally, chokes occur when horses eat too quickly without chewing properly. The feed doesn’t get softened with saliva and forms a dry mass that becomes stuck in the oesophagus. It’s more common in horses that are meal-fed, in greedy or hungry horses/ponies that gorge their food, and in those with dental problems.

Slow-feeders - that encourage horses to eat slower - are available for both hard feeds and hay feeds.

Some horses are predisposed to choke – especially older horses that have reduced saliva production. These horses also have a high incidence of dental abnormalities and often don’t chew so well. Miniature horses and foals can easily choke due to their small oesophagus.

Mild choke can be confused with a respiratory tract infection and with colic. Importantly, an episode of choke can resemble Hendra virus infection – which often presents as respiratory distress, increased respiratory rate and nasal discharge. Hendra virus exists in all areas of Australia where flying-foxes occur. It is classified as a biosafety Level 4 agent (defined as posing a high risk of life-threatening disease in people), and the use of safe work practices and personal protective equipment is essential to manage the risk of human exposure. Asking a vet to attend an emergency is so much easier if the horse has been vaccinated for Hendra virus – and laboratory studies have shown the vaccine is effective against the new strain of Hendra virus.

HOW DO YOU KNOW IF IT IS CHOKE? Choke often occurs soon after horses have been fed and the symptoms arise pretty quickly. Because horses can’t vomit or regurgitate food, one of the key features of choke is the appearance of food/fluid at the nostrils. This can be quite a large volume and may be a frothy white colour or stained green from grass and usually contains food.

Horses affected may stretch their neck and the neck muscles can have cramps and tremors; open their mouth wide; cough, snort, splutter, struggle to breathe and swallow properly; flap their lips, shake their head, gag and look alarmed with confusion in their eyes. Some horses might sweat and show signs of distress and discomfort, they may suddenly pull back from the feed bin, brace their neck - lie down and roll. While some may stop eating, others might continue to eat and drink and this worsens their plight.

IF THE COUGH IS LOST If the attack of choke is not cleared by the initial bout of coughing and heaving, the horse will move into a quieter phase of choke in which the reflex stimulation to cough is lost.

These horses or ponies can become bloated, depressed and stand with food debris and saliva coming out of their nostrils each time they swallow. Usually it comes from both nostrils, and

HENDRA AWARENESS: It’s also important to recognise that other conditions can resemble a choke episode and one of them is Hendra Virus infection.

Figure 1

Horses have a very long oesophagus, making them susceptible to lumps of food or foreign material sticking at some point on the way to the stomach. The most common sites of simple obstruction are: 1 the entrance to the oesophagus at the 1. back of the throat 2 2. the point where the oesophagus enters the chest 3.

3 the length of the oesophagus that travels through the chest 4 the point where the oesophagus enters the stomach 4.

Continued

1

2

3 4

Figure 1: Courtesy of DR. Sameeh M. Abutarbush

https://www.msdvetmanual.com/digestive-system/disorders of the esophagus

Oesophogus to stomach

Nasal Cavity

Epiglottis

Mouth

A horse that has Choke will stretch its neck down to try and clear the obstruction.

When there is a blockage, food debris and saliva comes out of the nostrils each time the horse swallows.

Trachea to lungs

NORMAL RESPIRATION

As the horse inhales during normal respiration, the air travels down the trachea, which divides into the tubes known as the right and left bronchi, then into the smaller airways called bronchioles in the lungs.

The oesophagus is the passageway from the mouth to the stomach. It contains rings of muscles that relax and contract to move the food down towards the stomach.

The epiglottis - a flap of tissue that sits over the top of the trachea - blocks food and drink from going down into the trachea to the lungs when the horse swallows. Occasionally while choked, the horse may breathe in fluid and/or food material into the trachea and lungs causing infection that may be fatal.

Oesophogus to stomach

Nasal Cavity

Epiglottis

Mouth

Choke continued... initially can be mostly feed and water, but often will turn from a clear to cloudy discharge. If the condition goes untreated, the horse may become dehydrated and severely depressed.

Depending on where the obstruction is, you may or may not be able to see a lump from the outside of the neck. There may be a ‘rattling’ sound as the horse tries to breathe around the saliva that is pouring out of its nose – this increases the risk of aspiration pneumonia, which is caused by feed material flooding down the windpipe (trachea) and into the lungs. Foreign material in the lungs can cause the horse to develop a secondary bacterial infection and pneumonia. If the oesophagus ruptures, death may follow due to shock and infection. Fortunately, this is not common, but to minimise these risks, veterinary attention should be sought early to resolve the choke as quickly as possible.

WHAT CAUSES CHOKE? A number of factors can lead to a choke episode, including not chewing feed completely - due to dental problems, such as missing or painful teeth, sharp points; eating too quickly and swallowing before adequate chewing; inadequate saliva production; partial obstruction of the oesophagus due to a tumour, scarring from old injuries or if there is a loose spot (balloon-like structure), known as a diverticulum, in which material can gather and set up a blockage.

Friesian horses are over-represented in this group due to a congenital or hereditary predilection to ‘megaesophagus’ – an enlargement of the oesophagus.

Choke can also occur due to a neuromuscular disease – the normal oesophagus has co-ordinated waves of contractions that move food down to the stomach. Certain neuromuscular diseases interrupt this.

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Trachea to lungs

SWALLOWING

Some horses pick up rocks, sticks, or other objects in the pasture, whether intending to eat them or just play with them, and these objects may become lodged in the oesophagus.

EATING TOO FAST Most horses get choke from just eating their meal too fast. Others, because they have been given food of a size that can lead to a blockage. This includes treats such as apple, carrot, corn-cobs or beet pulp.

If hay is changed, the new type may be more fibrous and the horse doesn’t chew it as well as it could. Because poor dental health makes horses prone to choke it’s really important that equine veterinary dental exams are performed regularly, especially in our older horses. Young horses can have issues as well, including caps or ‘baby teeth’ that don’t shed properly.

Younger horses may also be more inclined to pick up and chew foreign objects that can damage their teeth.

INADEQUATE WATER Another cause is inadequate water intake, which can occur if horses are fed too soon after strenuous exercise, fasted for any reason, suffer dehydration or if they have a general anaesthetic.

Horses that have been sedated for any reason should not be allowed to eat until they have recovered. Foals that chew bedding, shavings or dry, coarse hay or straw can also develop choke, and a detailed veterinary oral examination should be done to exclude other causes, such as a cleft palate or dental diseases.

WHAT TO DO

Fortunately, most episodes of choke clear on their own. However, they are one of the most common equine emergencies with potentially serious consequences, so your vet should be called without delay if the choke lasts longer than 30 minutes.

While waiting for the vet, encourage your horse to stand quietly with its head down, prevent eating by hand-walking or muzzling. It’s a potentially dangerous myth that you can resolve choke by pushing a garden hose in your horse’s mouth — this increases the risk of serious complications, especially aspiration pneumonia. Try to keep your horse and yourself calm - if your horse is alone, having a friend brought near may help it settle.

TREATING CHOKE The aim of treatment is to clear the obstruction. Your vet will insert a stomach tube to confirm that something is obstructing the passage into the stomach, at what level the blockage has occurred, how solid it feels and if it can be gently encouraged to pass on into the stomach.

Some horses need to be sedated or anaesthetised to reduce their pain and anxiety and to encourage relaxation of the muscles, which may be clamped tightly around the blockage. Small amounts of water and/or lubricant is then flushed, pumped and siphoned repeatedly via the stomach tube to slowly remove the accumulated feed material. This may take some time and can be extremely messy, especially if the horse is coughing and shaking its head around. In some chokes, carbonated drinks (such as cola) are added to the flush to help disintegrate and dissolve the accumulated mass. Some horses however, do require surgery.

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Continued

February/March 2022 - Page 19

Choke continued...

WHAT ARE THE COMPLICATIONS? The longer the choke is present, the more risk there is of damage to the oesophagus muscle and ulceration to the lining. This can lead to scarring and narrowing of the oesophagus and in severe cases the oesophagus may rupture. Other risks of choke include aspiration pneumonia. Horses can only inhale air through their nostrils (i.e. they can’t breathe through their mouth) and they are good at protecting their airway. However in choke, secretions and food can go down the windpipe (trachea) into the lungs and cause a nasty pneumonia that can be very difficult to treat. Signs of aspiration pneumonia begin to be apparent from around 24-48 hours after the choke episode.

Repeat chokers are also often endoscoped and might need to remain on ‘soupy’ mashes indefinitely. Many pelleted feeds are based on grain or grain by-products and don’t contain the proper mineral balance to be used as the major source of nutrition for the horse, so only use protein-based pellets that also provide correct levels of vitamins and minerals.

Following resolution of the obstruction it is important to monitor the horse’s temperature two to three times a day for at least five days because a fever might be one of the first signs of pneumonia.

Other signs include coughing, dullness, loss of appetite, impending laminitis, nasal discharge and increased respiratory rate or effort. If the choke lasted more than four hours or the horse has repeat episodes, they may need a 24 hour vet check, xrays, ultrasound or endoscopy.

All content provided in this article is for general use and information only and does not constitute advice or a veterinary opinion. It is not intended as specific medical advice or opinion and should not be relied on in place of consultation with your equine veterinarian.

Dr Jennifer Stewart CEO BVSc BSc PhD Dip BEP Equine Veterinarian and Consultant Nutritionist.

FOLLOW-UP CARE Once the choke is cleared the horse should be fed ‘sloppy’ feeds or grass for several days to allow any local swelling to subside. Dry feeds and hays should be avoided, instead, provide a soaked mash of pelleted feed for at least 7–14 days. Horses with mucosal ulceration should be fed this diet for 60 days, after which your vet may recommend endoscopy to check healing.

Dr Jennifer Stewart www.jenquine.com Equine Veterinarians Australia www.ava.com.au

Dr Jen Stewart is currently the only practicing equine veterinarian and clinical nutritionist in Australia with more than 40 years experience. Jen has been developing premium formulas for studs, trainers and feed companies - such as Mitavite - in Australia and around the world. Consulting to leading international studs and trainers in various countries while working on research projects and being involved in nutritional management of a variety of equine clinical conditions, including colic, tying-up, laminitis, performance problems, developmental orthopaedic diseases and post-surgery.

Jen’s vision is to provide world best-practice in equine veterinary nutrition and to BRING SCIENCE TO YOUR FEED BIN.

Reducing the risk of choke ●●

Soak dry foodstuffs

●● Cut hard treats to the size of your thumb and carrots lengthwise – the oesophagus can only dilate to about 5cm and anything larger is likely to get stuck ●● Always have clean water available ●● Some horses choke on a particular feed and access to this feed should be prevented ●● Ponies especially will eat too fast if they are food-obsessed and very excited about mealtime, if they have to compete for food, are threatened by another horse at feeding time or hungry because their feeding schedule has been disrupted. Placing smooth large rocks in the feedbin to encourage slower eating, providing smaller meals more often, providing a larger feedbin to spread the feed out and prevent the pony from taking large mouthfuls, a ‘slow-feeder’, feeding fearful horses alone, having a regular feeding routine and constant access to pasture or hay, can all help reduce the risk of choke ●● Regular dental health checks, dampening feed, soaking hay cubes or beet pulp, providing adequate daily salt and free water access all help saliva production. If a horse is dehydrated - as can occur with hot weather, low salt intake, poor quality water, heavy exercise, transport, lactation or restricted access to water - offer small amounts of very moist feed over multiple feedings until hydration levels return to normal.

There are many causes of dysphagia (difficulty swallowing) and excess salivation. Your vet will be able to rule these out and advise on management changes that can reduce the risk of future episodes. Prompt veterinary attention also reduces the risk of complications and in situations where you may not know how long an episode has been going on, your vet can help determine if immediate treatment is needed.