Flaxseed (also known as linseed) is a valued feed ingredient amongst horse people. How it should be used has long been the subject of considerable debate. Its safety for horses has always been under question and methods of preparation are many and varied. This FeedXL newsletter looks at what flaxseed can add to your horse's diet, if it is safe to feed and how it can be prepared for feeding.

What does flax add to a diet?
Flaxseed's best known attribute is its high Omega 3 essential fatty acid content.Flaxseeds are over 40% oil and more than 50% of this oil is the omega 3 fatty acid α‐linolenic acid. A horse's natural grazing diet is high in omega 3 fatty acids. However aswe add grains like corn and barley to a horses diet their diet can become skewed towardshaving high levels of omega 6 fatty acids. Flaxseed provides a 'natural' way to keep thelevels of omega 3 in a horse's diet balanced without using expensive omega 3 fatty acidsupplements. Adding 100 grams of flaxseed to your horse's diet will add over 20 ml ofomega 3 fatty acids.

While omega 3 fatty acids are generally the primary reason flaxseeds are fed to a horse,flaxseeds are a decent source of protein with around 24% protein and 0.9% lysine and alsocontain around 25% fibre.

When can flaxseed be used?
Flaxseed is useful for horses on a high grain (and therefore high omega 6 fatty acid) dietor when they are eating hay that has been in storage for some time or grazing low qualitypasture. Flaxseed may also be used when horses have a dry coat and skin, if they haveproblems with inflammation including arthritis and sweet itch/Queensland itch or when highomega 6 oils like corn oil or sunflower oil are being fed as an energy source in the diet.Flaxseed itself can be used as a source of energy in the diet and because of its high fatattribute is often found in supplements intended to promote weight gain in horses.

How should flaxseed be prepared for feeding?
Because flaxseed is such a small seed it is best to grind flaxseeds immediately prior tofeeding to break the seed coat, otherwise the seeds will pass undigested all the waythrough the gastrointestinal tract. It is important to grind the seeds fresh just prior tofeeding as the oils in flaxseed are prone to rancidity and will go off very quickly ifground and left exposed to air. A small coffee grinder is commonly used for the purpose ofgrinding fresh flax straight into a horses feed (very gourmet!).

It is possible to purchase pre‐ground and stabilised flaxseeds if grinding your own is notan option.

Does Flaxseed have to be boiled before feeding?
Tradition says that flaxseed must be boiled before feeding it to a horse because of therisk of Prussic Acid (or hydrogen cyanide) poisoning. Anyone who has boiled flaxseed knowshow messy it gets and for most the effort and mess are too much to continue persisting.Well good news ... flaxseed it seems can be fed safely without being boiled.

Flaxseed contains compounds called cyanogenic glycosides. When the flaxseeds are chewed upby a horse these cyanogenic glycosides come into contact with an enzyme (β‐glycosidase)which converts it to hydrogen cyanide, which can then lead to cyanide poisoning. HOWEVER,the β‐glycosidase enzyme is destroyed by the acidic environment of the horse's gastricstomach, meaning the cyanide is never produced in quantities large enough to cause anyproblems. This means you can feed flaxseed without cooking it first.

A study published in theCanadian Journal of Veterinary Research in 2002 looking at the ability of flaxseed toreduce the inflammation associated with culicoides hypersensitivity (sweet itch orQueensland itch) reported that they fed 1 lb of flaxseed per 1000 lb of bodyweight tohorses (or 0.5 kg per 500 kg bodyweight) over a period of 42 days with no negative side‐effects being observed. With this dose rate being much higher than the normal 1 to 2 cupsfed per day it can be concluded that flaxseed is safe to feed to horses without cooking itfirst.

What about soaking it?
It is possible that soaking flaxseed may actually make it dangerous as soaking the seedswould, to some extent, allow the β‐glycosidase enzyme to come into contact with thecyanogenic glycosides and allow for the production of hydrogen cyanide. So it isrecommended you do not soak flaxseed before feeding.

Can flaxseed meal be fed?
Flaxseed meal is the high protein (32%) meal left over after the flaxseed oil has beenextracted from the seed. Flaxseed meal can be fed to horses, however because the meal hashad most of the oil extracted its primary use in a horse's diet is as a proteinsupplement. The risk of cyanide poisoining from flaxseed meal is a little unclear. Becausethe seed is crushed during the oil extraction process it is possible for the β‐glycosidase enzyme to come into contact with the cyanogenic glycosides, so it is likelyhydrogen cyanide will be present. If you wish to feed flaxseed meal, look for mealproduced using heat extraction technology as opposed to meal made from seeds that werecold pressed. There are however far better sources of quality protein available includinglupins, full fat soybean, soybean meal and canola meal, without the possible riskassociated with flaxseed meal.

Other possible side effects
Flaxseed contains phytoestrogens. Phytoestrogens are naturally occurring plant compoundsthat are structurally similar to estrogen. Studies in rats (Collins et al 2003) have foundthat feeding high levels of flaxseed to rats increased the number of female rats withirregular estrous cycles, suggesting flax could have a negative impact on the fertility ofbreeding animals. If you are breeding your mares and having any type of fertility problemsit would be wise to avoid flaxseed in their diets.

Summary
Flaxseed is a useful feed ingredient for horses. It can be used to increase a horse'somega 3 essential fatty acid intake where dietary omega 3 levels are low or when higherintakes of omega 3 for a particular horse seem beneficial. Despite popular opinion thatflaxseed must be cooked prior to feeding to avoid hydrogen cyanide poisoning, studies haveshown that up to 1 lb/1000 lb bodyweight (or 0.5 kg/500 kg BW) can be safely fed withoutcooking. Flaxseed should not be soaked prior to feeding and they should be avoided in thediets of breeding mares with a history of reproduction problems. FeedXL can be used toincorporate flaxseed into your horses diet so that it balances well with other feedingredients being fed.

Dr. Nerida Richards (PhD) is Australia's foremost expert in Horse Nutrition. This articleis courtesy of FeedXL DIY Diet Plannerfor Horses. If you would like be among the first to receive FeedXL newslettersthen please consider subscribing to FeedXL.

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