When I am asked which is preferable: linseed oil or flaxseed oil, my response is, “Neither,” (or perhaps I should say "both") - linseed and flaxseed are one and the same!
Reprinted with permission of Jessica Jahiel, PhD, HORSE-SENSE Newsletter
One warning, though: The linseed oil (AKA flaxseed oil, AKA flax oil) you feed to your horse should be FOOD GRADE OIL - that is, cold-pressed or extracted in some other manner that does NOT involve the use of a solvent. Solvent-processed linseed/flaxseed/flax oil should NOT be fed to horses. Solvent-processed linseed oil is a very useful product if you happen to be a painter, someone who restores paintings, or a furniture maker or refinisher. Don't use anything called "boiled" linseed oil - it sounds natural and nice, but in this context, the word "boiled" has nothing to do with the sort of boiling one might do in the kitchen. "Boiled linseed oil" means "Linseed oil with solvents added." Once again, this is not something that should be fed to your horse.
Some readers ask whether linseed MEAL might be preferable to linseed oil. The answer: Probably not.
Long ago, when linseed oil meal (ground linseed) was a popular element in the diets of many horses, the seeds were ground and the resulting meal was fed directly to the horses; this left most of the oil IN the meal. For this very reason, rancidity was always a concern, and people found various ways of dealing with it. Some (sensibly) decided to grind small quantities of meal each day (using, say, a coffee grinder) and then feed it immediately so that rancidity wouldn't be an issue. Other people simply discontinued the practice of feeding linseed meal.
Nowadays there are different processing methods in use, and the results are both good and bad.
Modern-day linseed meal is much less likely to go rancid - but that's because it contains much less oil! The modern methods of processing remove most of the oil from the meal, leaving a residue that's much lower in oil and thus much lower in the Omega-3 fatty acids that were the main reason you wanted to feed linseed oil in the first place! So if you can find pure, cold-pressed linseed/flaxseed/flax oil, that's probably your very best bet.
Do keep the rancidity issue in mind, though, and avoid buying large containers of oil unless you have a great many horses to feed. If you have only one or two horses and you feed the typical recommended amount (that is, 3 or 4 tablespoons per day) a large container of oil may well go rancid before you use it up. In any case, keep the oil in a cool, dark place.
Since 1995, Jessica Jahiel, award-winning author, clinician, and lecturer, has been answering questions from subscribers through her HORSE-SENSE Newsletter, a free Q&A newsletter dealing with all aspects of horses, their management, riding, and training. www.horse-sense.org