Feeding Flaxseed

for the β glycosidase enzyme to come into contact with the cyanogenic glycosides so it is likely hydrogen cyanide will be present. If you wish to feed flaxseed meal look for meal produced using heat extraction technology as opposed to meal made from seeds that were cold pressed. There are however far better sources of quality protein available including lupins full fat soybean soybean meal and canola meal without the possible risk associated with flaxseed meal.
Other possible side effects
Flaxseed contains phytoestrogens. Phytoestrogens are naturally occurring plant compounds that are structurally similar to estrogen. Studies in rats Collins et al 2003 have found that feeding high levels of flaxseed to rats increased the number of female rats with irregular estrous cycles suggesting flax could have a negative impact on the fertility of breeding animals. If you are breeding your mares and having any type of fertility problems it 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 horses omega 3 essential fatty acid intake where dietary omega 3 levels are low or when higher intakes of omega 3 for a particular horse seem beneficial. Despite popular opinion that flaxseed must be cooked prior to feeding to avoid hydrogen cyanide poisoning studies have shown that up to 1 lb1000 lb bodyweight or 0 5 kg500 kg BW can be safely fed without cooking. Flaxseed should not be soaked prior to feeding and they should be avoided in the diets of breeding mares with a history of reproduction problems.