Tips & Hints

Blood Testing

Having your horses blood-tested once a year for their selenium level is highly recommended. Too much or not enough selenium can lead to health issues - in some cases serious, when levels are very low or very high. Very low levels - less than 1000 can result in poor muscle development, poor coat and hooves, ill thrift and general ill health. Ideal levels for selenium are at the top end of normal - 2800-3200. 

Electrolyte levels - Calcium, Magnesium, Potassium, Sodium and chloride are all electrolytes. These dissolved ions are essential to many biological functions, and abnormally high or low levels can have a significant impact on health. Electrolyte levels in the blood can change quickly, due to dehydration, loss through diarrhea or via urine, from lush grass or high protein feeds. 

Elevated potassium can be caused by horses consuming lush grass that is high potassium. The resulting condition, termed "Hyperkalemia" is very common in New Zealand horses grazing pasture. Salt is very often not fed adequately. Horses do not feel thirsty when salt intake is inadequate and the excess potassium is not excreted via the kidneys as it should be as the horse fails to drink. 

Symptoms of hyperkalemia can range from mild spooking, shying, tight and tense muscles, hallucinating, aggressive crazy behavior, sweating easily, thick-windedness to life-threatening colic or a staggering type condition know as Grass Tetany that is seen in cattle. 

If your horse has these symptoms, removing him from pasture immediately and calling the vet is essential. Horses sometimes require saline drenching or IV saline due to severe dehydration. 

Feeding adequate sodium and magnesium and avoiding grazing horses on short very lush pasture is absolutely essential to ensure this potentially life-threatening condition is avoided. Salt (sodium chloride) should be fed at 10g per 100kg MINIMUM. 

Ensure good quality hay is always available.  

 Magnesium levels are not well represented on a blood test due to the homeostasis mechanism. This mechanism ensures blood magnesium levels are kept up even though levels throughout the rest of the body such as the nervous system may be very depleted. Magnesium should be fed daily at good maintenance levels to ensure excellent health and behaviour. 

Avoid adding potassium

Check all feed labels. If you are struggling with a horse that has any of the symptoms listed above, do not feed anything containing potassium including store-bought electrolyte mixes, lucerne chaff or so called fibre products containing alfalfa or high protein feeds.

Adding potassium from a supplement should only be done after blood tests confirm levels are low. Adding potassium when levels are already in excessive, as  already discussed,  can be very counter-productive. Cells become flooded and muscles cannot function properly. Mental confusion can also occur. Horses appear "away with the fairies" 

Some cheaper/inferior mineral supplements contain potassium or those formulated for other countries where pasture is not fed. Your horse will be getting more potassium than it needs from pasture/feed even when it is in hard work. 

Avoid feeding

Do not feed kelp or garlic. Kelp contains potassium and high levels of iodine which horses don’t require. Garlic is poisonous for horses.

Avoid products containing rye/clover, even if labelled endophyte free, and rye/clover pasture and hay. They are high in sugar and are not easily digested by horses. Rye and clover can also cause photo-sensitivity which can lead to various skin disorders like mud fever and problems like head-flicking.

A bit about protein

Horses with difficult behaviors or any of the symptoms listed above can be greatly improved by reducing protein in the diet if this is being fed in excess of  the horse's needs. This excess protein converts into urea in the bloodstream which is toxic to the animal. This toxicity can result in aggressive behaviour towards people and other horses.

 Restings horses get enough protein from hay and often more than they need from grass. Feeding a good quality chelated mineral supplement enables your horse to utilize protein in his diet much more effectively and so is cost effective and healthy solution for your horse. 

High protein feeds such as: soya bean meal, rice bran and whey protein concentrates may be best to be avoided if your horse has any of the listed symptoms. 

Adding calories in the form of oil which is fat rather than protein is a very good option. Oil is calorie dense which means small amounts can be fed reducing overall feed bulk. 

Oil is great

Oil is a fat, not a protein. Oils are calorie dense and when introduced into the diet gradually, are digested well by horses. More calories can be added without overfeeding on grains (carbohydrates) which tends to overload the horse's hindgut. 

Cold pressed flax seed contains the highest percentage of anti-inflammatory omega 3 of any plant oil and horses love the taste too!

Duwell Flaxseed oil is rich in Omega 3 due to our cold-storage policy. Omega 3 is lost after only 3 weeks when left out of the fridge. 

Avoid feeding oils high in omega 6 such soy and canola as these are inflammatory.  


Good quality hay is the greatest investment you can make for the health of your horse but often is in "the too hard basket".  

Horses evolved to eat diets high in fibre and low in calories consumed over most of the day. It is very unhealthy for horses go for more than a few hours with nothing to eat. Unfortunately this happens often and is one of the main reasons stomach ulcers are so prevalent now. 

It is also the most inexpensive fibre you can feed your horse. So often customers ring with concerns about adding enough chaff to their horses feed but they have forgotten about hay. Spend less on chaff and more on hay is what I recommend. 

Mixed pasture hay can be sourced in most areas by contacting local contractors or farmers.

Horses in light work, correctly supplemented with vital minerals, can happily live on hay and in fact do better than those on so called ‘good grass’. Here on the DUWELL farm we have had dozens of horses on hay diets for years at a time and have seen over and over the tremendous health and behavioral benefits this brings. 

This boy has been off grass for 4 months. He is a big boned WBx around 16.3hh

15.3hh Morgan x. He lived on a hay diet for 2 years and you can see he is in exceptional health! 

Hoof quality improves on a mainly hay diet as biotin is a bi-product of feeding hay. No hoof supplements needed! Poor hooves are a direct result of poor mineral and fibre provision in the horse's diet. 

Feeding hay is a good way to improve behaviour. Gut function can be compromised from lack of fibre and too many calories can be consumed. Hay contains fewer calories than green grass and is more balanced in its mineral content unlike short green grass.

The best way to avoid stomach ulcers, boredom or hunger related behaviour is to supply adlib hay. Approx 5-6 slices for a 500kg horse per day should be allowed for a horse off pasture.

Avoid hay containing rye or clover. Stalkier hay is often more ‘horse friendly’ than fine good looking hay.

Keep feed available

Ensure your horse always has something to nibble on. Stomach ulcers can begin within 4 hours if a horse has nothing to eat.


Do not starve a fat horse to get it to lose weight. This can cause liver damage. Ensure adlib hay is available and soak if necessary to lower calorie intake.