Linseed, is it safe?
Some say linseeds are poisonous and should never be fed in any form and others say the opposite
Linseed - Linum usitatissimum |
The current wisdom depends on who you ask! Dr Deb Bennett (biomechanics expert but not in nutrition) advocates flax or linseed is a poison and should never be fed yet Dr Eleanor Kellon VMD and Dr Susan Evans Garlinghouse VMD, another equine nutritionist both advocate it's fine in reasonable amounts. Dr Lydia Gray VMD states clearly on her 'Askthevetpage blog' that feeding flax/linseed is safe. Dr Gray says feeding linseed is harmless because "a recent study confirmed that stomach acid inactivates the enzymes that interact with the cyanogenic glycosides to form cyanide so that is why toxicity is not observed" and advises feeding the ground up seeds soon after grinding. However I haven't been able to locate the study that substantiates this statement.
Linseed or flax (Linum usitatissimum) is the only oil seed that contains the ratio of omega-3 fatty acids (anti inflammatory) to omega-6 fatty acids (pro inflammatory) in roughly the same ratio as grass, about 4:1. Linseed oil contains roughly 58% omega-3 and 14% omega-6 fatty acids. Both omega-3 and 6 fatty acids are essential in the diet, they have to come from food sources whereas the others can be manufactured by the horse. Rice bran, sunflower seeds and any other oils are high in the pro inflammatory omega-6. Sunflower seeds contain zero omega-3 fatty acids. For a comparison check out the levels here in the 'Which oils are you using now? table' but note, Mitavite left out linseed. [Note: Performer 3 Oil is fish oil, is fish oil appropriate for horses? It's a personal choice but Performer 3 Oil is too high in omega-6 compared to omega-3 in my opinion. See below for a discussion comparing fish oil vs linseed]
The Slow Discovery of the Importance of 3 Essential Fatty Acids in Human Health and The Benefits of Flaxseed explains in more detail about the benefits of omega-3 fatty acids. The study The effects of dietary N-3 and antioxidant supplementation on erythrocyte membrane fatty acid composition and fluidity in exercising horses documented the reduction in red blood cell deformity due to exercise with omega-3 fatty acid supplementation.
Fat or oil in hays is roughly 50% of the level in fresh grass but the loss is almost entirely omega-3 as the fatty acids are heat sensitive. The curing process to turn grass into hay destroys the omega-3s. Linseed is mainly recommended as a fatty acid supplementation for horses on predominantly hay diets as they miss out on the omega-3s.
Why is linseed a concern?
The seeds contain little, to no, preformed hydrogen cyanide but hydrogen cyanide, also known as prussic acid is produced when enzymes come into contact with cyanogenic glycosidesthat are normally kept separated in the cell vesicles. This occurs with grinding or contact with water.
Strains of linseed used for human consumption typically have low levels of cyanogenic glycosides. Also, hydrogen cyanide is a gas and will vaporise off the meal as it is released from hydrocyanic acid. Heat treatment of the meal to lower the moisture content will also greatly decrease it. Freshly milled linseed meal may be as high as 500 ppm according to some EU sources, but this will drop even during the oil extraction process.
To put the risk in perspective, cattle and pigs have been fed diets containing as much as 15% linseed by weight with no toxicity. In 'Plants causing sudden death', it was reported that ruminants like cattle "are more susceptible to cyanide poisoning than other animals" and that "Humans, pigs, dogs, and horses that have a highly acidic stomach (pH 2 - 4) tend to have a reduced rate of glycoside hydrolysis and cyanide production in their digestive systems and therefore rarely suffer from cyanide poisoning of plant origin". Dr Kellon VMD said she has never ever seen a report of cyanide poisoning from linseed in a horse. The Canadian sweet itch study used human grade stabilised linseed, about 450 grams/450 kg bodyweight per day and reported no issues. This page has tips for Queensland Itch.
It has to be a personal decision by the horse owner about what they feel comfortable feeding. If not comfortable with grinding the seeds then simply use linseed oil as the cyanogenic glycosides and enzymes are not in the oil component of the seed, the oil is definitely safe. Look for cold pressed or animal grade linseeds. Cold pressed/animal grade means the oil has been squeezed out of the seeds without heating the seeds as the heat destroys the fatty acids. The oil to avoid is furniture grade linseed oil as it contains solvents to expediate the drying time when used on furniture, tool handles. A good reference to read about furniture grade linseed is at The Natural Handyman website. If you buy linseed oil from a hardware, assume it's for furniture, not horses.
Unprocessed oils frequently have opaque, thick yellow material in the bottom. This is lignans and other material from the linseed, rich in plant antioxidants and vitamin E. If the oil is not refrigerated there will be a rapid loss of omega-3s although there may be some protection from the natural antioxidants.
Boiling linseeds will destroy the omega fatty acids, if the purpose was to supplement omega-3s then boiling makes it pointless. In the UK and US, horse owners can buy ground stabilised linseed or flax, unfortunately we don't have that choice here in Australia. It is more expensive so many skip it and buy the seeds like many of us do in Australia and grind them. Horsetech and other companies use a process that preserves the omega fatty acids but possibly inactivates the enzymes (they won't say how the process works).
Feeding whole linseed is considered not as good. If you take some whole linseed and put it in a little vinegar, or even milk and just let it sit you will see a gel starts to form within an hour or so. The same thing likely happens inside the horse even if the seeds are not broken by chewing. Is this as effective as grinding the seeds, we don't know for sure.
Do you need to supplement linseed?
If your horses are predominantly on pasture then no, your horses are likely to be getting plentiful anti inflammatory omega-3 fatty acids from grass. If your horses have hay as the main forage then the answer is yes as curing hay destroys the omega-3s.
Fish oil vs Linseeds
There are 3 major types of the anti inflammatory omega-3 fatty acids; alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). These are essential fatty acids, they have to come from the diet for people so human studies looks at the three and how they work in our bodies. There are lots of benefits. Once eaten the body converts ALA to EPA and DHA, the two types of omega-3 fatty acids more readily used by us. Fish get their ALA from plant material and convert it to EPA and DHA.
Plant material is a rich source of ALA but does not contain preformed EPA or DHA. Since a horse's natural diet is plant material and not fish I find it puzzling that companies are pushing fish oil which is highly unpalatable for horses unless heavily processed. This article from KER is a great example of how companies push fish oil as a feed additive for horses. Very persuasively written.
The article above says that that the ability of horses to efficiently convert ALA to EPA and DHA is not known, and thus requires more research. That also means there is no proof or reason at this point to to believe horses don't easily convert ALA.
Whether ALA can convert efficiently into EPA or DHA or not is of lesser importance to me if a herbivore like the horse didn't evolve on a diet that included EPA or DHA so I'm lost as to why fish oil is considered beneficial for horses. Fish oil is well established as beneficial for people which makes a lot of sense since we are omnivores. The idea ratio of omega-3 to omega-6 fatty acids is higher in omega-6 in animals like us that are higher up in the food chain.
References
J Alonzy Linseed oil - it's use and limitations
The Natural Handyman
http://www.naturalhandyman.com/iip/infpai/inflin.html
Dr Eleanor Kellon VMD
http://drkellon.com/
An interview for Long Riders Gear: http://campaign.constantcontact.com/render?v=001rxOp_4aBK0qzXsz61XS_KzdRr9InbNPPR4hrWf9YhAOJYAnuwtKEZIt_yIQ-7-6vPnM8Ql-XXg3Ma3n34mhoBlgoEticT_0OSK-k5tmI5d2aynA1pYwl_cB5a73C3aLtm1emI1abXOsJwtpFbgbsPpRvikSxhg380GI2H76lnbbeNmC64WiIAw%3D%3D
Dr Lydia Gray VMD
http://askthevet.smartpak.com/equine/misc-topics/is-flax-seed-safe-to-use-in-horses/
R.T Holman (1998) The slow discovery of the importance of 3 essential fatty acids in human health
The Journal of Nutrition
http://jn.nutrition.org/cgi/content/full/128/2/427S
A.P Knight and R.G Walter (2002) Plants causing sudden death
http://www.ivis.org/special_books/Knight/chap1/chapter_frm.asp?LA=1
K Portier, B De Moffarts, N Fellman, N Kirschvink, C Motta, C Letellier, A Ruelland, E Van Erckt, P Lekeux and J Coudert
The effects of dietary N-3 and antioxidant supplementation on erythrocyte membrane fatty acid composition and fluidity in exercising horses
http://bictel.ulg.ac.be/ETD-db/collection/available/ULgetd-07232007-164244/unrestricted/EVJ.pdf
E. Magee The benefits of flaxseed
http://www.webmd.com/diet/features/benefits-of-flaxseed
DHA/EPA Omega-3 Institute Metabolism of Omega-6 and Omega-3 Fatty Acids and the Omega-6:Omega-3 Ratio
http://dhaomega3.org/index.
Kentucky Equine Research Inc Omega-3 fatty acids: Consider the source
http://www.thehorse.com/ViewArticle.aspx?ID=15382
Mitavite - Which oils are you using now?
http://www.mitavite.com.au/
T.D Maddock, V.L Anderson, G.P Lardy Using flax in livestock diets
http://www.ameriflax.com/as1283.pdf
W O'Neill, S McKee, and A. F Clarke (2002) Flaxseed (Linum usitatissimum) supplementation associated with reduced skin test lesional area in horses with Culicoides hypersensitivity
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC227015/
Contact details:
Carol Layton B.Sc, M.Ed
Balanced Equine Nutrition
Phone: 02 4953 2580
Email:
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