Anaemia and lethargy… feed related problems or not?

Has your horse got more whoa than go and are you concerned that there is something wrong? Or has your horse been diagnosed with anaemia? Are you considering trying to help the problem with feed or supplements? Read on to learn more about energy, how feed affects energy levels, and how to deal with anaemia. 

What is energy?

We tend to talk about two very different types of energy for horses – dietary (feed) energy and temperament or behavioural energy (how forward going or not your horse is). Dietary energy is measured in calories (called megajoules or MJ in horse feed, and calories or kcal in people) and is not the same as energy expressed in behaviour i.e. a fizzy or exuberant or slow and dull horse. Dietary energy is extracted from nutrients including carbohydrates, fats and oils and to a lesser extent protein, and is either used immediately or stored for later use.

Increasing dietary energy will cause weight gain, and reducing it will cause weight loss. Dietary energy fed in excess is stored as fat, for use in the future when there is a dietary energy deficiency. The fat is then broken down and used as and when required when dietary energy is insufficient for the horse’s activity level. In some horses specific sources of energy might cause more behavioural energy or exuberance. Some horses do react to certain sources of energy with extra exuberance, and the feeds that have been associated with this effect are starchy cereal grains including oats, barley and maize.

Conversely, too little dietary energy in a healthy horse with a healthy bodyweight does not cause lethargy; instead it causes weight loss. A horse who is lethargic due to a lack of dietary energy would also be very thin because the energy deficiency would have been going on for some time before it affected the horse’s behaviour.

Lack of behavioural energy

If a lack of behavioural energy comes on suddenly, or your horse is much more lethargic than normal, consult your vet. First, you need to rule out health problems. If your vet finds that your horse is anaemic, read on to the next section for more information. The most common cause of a lack of energy and forwardness is due to it being part of the horse’s innate temperament i.e. he is a ‘short’ horse. The most important factor to help such horses is to maintain a healthy bodyweight and avoid excess body fat gain. Excess weight can cause a lack of energy.

The most effective ways to give a horse more energy in his behaviour is 1. to get him fitter via a conditioning exercise programme and 2. to become a more effective handler and rider. Unfortunately there are no legal feeds or extra nutrients that can guarantee a more energetic horse. As mentioned above, some horses do react to certain sources of dietary energy with extra exuberance. Unfortunately adding extra cereals to the diet of a horse that is prone to weight gain is usually not to be recommended, because these types of horses generally use the extra feed energy to lay down fat, rather than express more exuberant behaviour. You could try adding oats or a racing coarse mix to try and liven up your horse, but you must monitor his weight carefully and if you see no behaviour effect, you should stop feeding them. In addition, research has shown that starchy feeds may cause a horse to be more reactive and less attentive rather than simply more forward going.

Effective training also helps impulsion and a horse’s willingness to go forwards. Developing your horsemanship will help you to become more capable as a horse rider and trainer, and your horse will become more responsive.


A lack of energy may be associated with anaemia. Anaemia is not a disease but a symptom of a problem. Having anaemia means your horse has a low level of haemoglobin in his blood, which is the pigment that carries oxygen to his tissues. This can be caused either by a low red blood cell count, a low level of haemoglobin in the red blood cells, or a combination of both. It is important to try and understand why this problem is present, rather than simply trying to treat it. Anaemia can be caused by a loss of blood, which may be acute or chronic. Chronic cases can be due to a high worm or lice burden, causing small but ongoing blood loss. Anaemia can also be caused by poisoning and chronic inflammation or infection. Encourage your vet to diagnose the underlying problem.

Anaemia should not be treated just with iron supplements. Anaemia in horses, unlike in people, is rarely caused by iron deficiency because most horse feeds, particularly forages, are rich in iron. Also iron is efficiently recycled within the body, rather than being lost when old blood cells are destroyed and new ones created, as happens continuously. Instead of giving an iron supplement to an anaemic horse, after the problem has been diagnosed and treated by the vet, the diet should be carefully balanced to ensure adequate intake of all essential nutrients. The most useful supplements are multi-vitamin and mineral mixtures containing useful levels of iron, copper and zinc. Note that some ‘blood boosting’ supplements are not broad spectrum, therefore are not suitable. Iron cannot be incorporated into haemoglobin without copper. Dietary iron alone will not increase red blood cells or increase the concentration of haemoglobin. Excessive intake of iron by horses is toxic, causes liver damage and may cause gastrointestinal disturbances and other mineral deficiencies.

Many myths surround energy levels of horses and how to treat both lethargy and anaemia. Ensuring your horse is healthy, receives a well balanced diet, and is not overweight, then both conditioning him physically with a fitness programme and working on your abilities as a horseman or woman are the best ways of increasing energy levels. If in doubt about his health, always consult your vet, and if anaemia is diagnosed, encourage your vet to investigate the cause of the anaemia, which will allow more effective treatment.