Aqueos - Boosting your horse’s immunity in the winter

Aqueos - Boosting your horse’s immunity in the winter

During these challenging Covid times, many of us want to feel like we are doing whatever we can to boost our own immunity – but have you thought about what you could be doing to boost your horse or pony’s immunity this winter? Little changes may help to avoid unwanted periods of illness; read on to find out more about how you could support your horse or pony’s immune system this winter.

Feeding changes

As the nights draw in, your horse or pony’s regime may well change – will you start bringing them into their stable overnight? Will there be a change of grazing? Will you introduce any additional roughage or feed to their diet, as the amount of grazing available reduces?

Although often unavoidable, changes in routine and feeding are not only a potential risk factor for colic, but may also have an impact on your horse or pony’s immune system. This is because sudden changes in feed or roughage can alter the microbiome of the horse’s gut. The microbiome plays an important role in the immune function of the digestive tract, and therefore any change in the microorganism population in the gut may, in turn, reduce the digestive tract’s resistance to infection.

Changes in your horse or pony’s feeding regime should be kept to a minimum wherever possible; however, if unavoidable, changes should always be made gradually – ideally over a period of one to two weeks. Feeding a prebiotic, probiotic, or postbiotic to counteract any unavoidable feeding changes may help to support the gut’s microbiome and allow it to recover more quickly to feeding changes, and therefore maintain optimum gut immunity.

Older horses

For several reasons, older horses’ immune systems may not be as robust as they were earlier in their lives. Their dentition (or lack thereof) may make it more difficult to chew food properly, meaning the length of fibre reaching the hindgut is increased, making it harder for the horse to digest. This can result in changes to the microbiome in a horse’s gut and may therefore compromise fibre digestion and the fermentation process that occurs in the hindgut, subsequently reducing the production of energy by these hindgut microorganisms. Ensure that your horse or pony’s dental care is up to date ahead of the winter months to reduce the impact of any age-related dental problems.

If you have any concerns that your horse or pony may be showing signs of Cushing’s disease (pars pituitary intermedia dysfunction), then the autumn is a good time of year to ask your veterinary surgeon to test for this condition. If your horse or pony is diagnosed with Cushing’s, treating and controlling the condition with medication can limit its impact on their immune system. Cushing’s disease impairs neutrophil function (a type of white blood cell) and therefore horses and ponies with untreated or poorly controlled Cushing’s disease are at an increased risk of opportunistic bacterial infections.


You may want to check that your horse or pony’s vaccinations are up to date – do not be tempted to let these lapse as your horse or pony gets older, it is still important to keep them protected. This is an easy way of ensuring that your horse should recover more quickly if he is unlucky enough to contract a disease that can be vaccinated against. This is because his or her immune system has been primed by the vaccination and so can produce antibodies against the infection more quickly.

All horses should be vaccinated against tetanus as a minimum, as unfortunately if contracted, treatment options for tetanus are limited and the outcome is often fatal. It is also strongly recommended to vaccinate horses and ponies against equine influenza, especially those that are mixing with other equines, such as those who go out to competitions regularly, or those on large livery yards with lots of horses coming and going.

Depending on your circumstances, you may also wish to consider whether to vaccinate against additional illnesses such as equine herpes virus and strangles. This may be influenced by whether your horses and ponies leave your yard or field, and how likely they are to come into contact with other equines when they do. 


You should make sure that your horse is following an appropriate worming programme and their worming is up to date, as if your horse has to fight off an infection alongside a high worm burden, this could potentially have a negative impact on their immune system and result in a slower recovery.

The excessive use of wormers is not recommended due to potential problems with resistance developing; however, the strategic use of wormers alongside faecal worm egg counts and potentially saliva/blood tests for, e.g., tapeworm, should be performed as recommended by your veterinary surgeon or suitably qualified person (SQP). Of particular importance at this time of year is to make sure that your horse has been dosed for encysted redworm ahead of winter, and that they have either received a negative tapeworm test or a tapeworm dose within the last six months.

Herbal supplements

A good-quality diet is always important to ensure optimal immune function; however, some herbal supplements may also help to improve immunity. Many of these herbs support immunity through their antioxidant effects. Antioxidants reduce oxidative damage to cells that are responsible for the body’s immune response, and therefore may limit the impact of infections, whether these are bacterial, viral, fungal, or parasitic. Watch out for the following ingredients if you are looking for a herbal supplement to support your horse or pony’s immune system this winter.

ginseng – may stimulate lymphocytes (a type of white blood cell) to produce antibodies and destroy cells that have become abnormal following an infection (NB this should not be fed to horses or ponies receiving non-steroidal anti-inflammatory drugs such as ‘bute’ (phenylbutazone) due to their potential interaction with ginseng)

ginger – supports normal immune cell functioning (NB ginger should not be fed to horses or ponies suspected or confirmed to have equine gastric ulcer syndrome as it can irritate the digestive tract)

garlic – when fed in appropriate quantities garlic can have anti-bacterial, anti-viral, anti-fungal, and anti-parasitic benefits that therefore support the immune system (NB can cause anaemia if fed in excess)

flaxseed – another useful antioxidant, however, this should not be fed to horses undergoing treatment for gastric ulcers as the stomach may not be able to inactivate the potentially toxic cyanide enzymes that can be present in flaxseeds

echinacea – an immune stimulant that is most beneficial when fed in the early stages of an infection; it can improve the cell signalling required for a co-ordinated immune response, and improve both lymphocyte and neutrophil function (another type of white blood cell)

evening primrose – a source of potent antioxidants and supports immune system function

rose hip – may increase the levels of vitamin C in the bloodstream (vitamin C is a known antioxidant)

cranberry – has useful antioxidant properties as it is rich in vitamin C

yucca – may help to increase antibody numbers, has anti-bacterial/anti-fungal properties, and also has antioxidant properties

other useful antioxidants include aloe vera, lavender, and milk thistle (NB aloe vera should not be fed during pregnancy as it may increase the risk of abortion)

Managing stress

Avoiding unnecessary stress for our equine friends is also important in ensuring that their immune system is not compromised. This may be as simple as keeping them in a structured routine that suits your individual horse or pony, and keeping companions together, but could also include ensuring that any potential medical or orthopaedic issues are investigated and treated as appropriate.

Take home message

Ultimately you may not be able to completely avoid your horse picking up a bacterial, viral, fungal, or parasitic infection this winter. But being prepared through preventative healthcare measures such as vaccinations, dental care, appropriate deworming, and avoiding stress may help to limit the impact of any such infections, and help to get your horse or pony back to full health as quickly as possible.

Although the evidence behind the use of herbal remedies or supplements to improve immunity is anecdotal, in most cases it is unlikely to do any harm (see above for any contraindications), so you may be keen to do what you can to support your horse or pony’s immune system alongside their usual diet. 

Article written by Dr. Jessica Putnam BVMedSci(Hons) BVM BVS(Hons) MRCVS