The Latest on the Omegas (Fats)
- Aug 1, 2006
The question: If omega-3 fatty acids benefit human health, can they provide similar benefits for horses? Although there have been only a handful of omega-3 studies for the horse, here's what we do know, and what researchers are hoping to find out.
(Editor's Note: If you are like many of us and don't know your omega-3s from your omega-6s, get up to speed with our Quick Facts sidebar on page 54 before reading on.)
Fat and Food Sources
When it comes to adding energy to the equine diet, a fat is a fat is a fat, but not when it comes to conveying omega-3 and omega-6 properties.
Explains Joe D. Pagan, PhD, president of Kentucky Equine Research near Versailles, Ky., "Some oils are high in omega-6, but lower in omega-3--corn oil, sunflower oil, and safflower oil--while others such as soybean and canola oils are moderately high in omega-6. The oils that contain more omega-3 than omega-6 are flaxseed and linseed oil, but the highest ratio of omega-3 to -6 is found in fish oil."
Ratios vary significantly as well between fresh pasture, hay, and grain. A two-year study conducted by Lori K. Warren, PhD, assistant professor of equine nutrition, University of Florida, found that bahiagrass (a warm-season grass common to Florida and the southeast) contained more omega-3 than omega-6 (40-55% of the fat in fresh pasture and 18-35% of the fat in hay is made up of omega-3).
"Compare this to cereal grains, where 50% of the fat is omega-6 and very little is omega-3," she notes. "Although forages only contain about 2-3% crude fat, a horse consuming a high-forage diet will actually be consuming a significant amount of omega-3 fatty acids."
Because of promising results in other species concerning inflammation and immune function, researchers are looking for similar effects of omega-3 fatty acids in the equine. So far, results are mixed.
Researchers at Kansas State University (KSU) examined the effects of docosahexaenoic acid (DHA) supplementation in reducing airway inflammation and exercise-induced pulmonary hemorrhage (EIPH).
"EIPH is a major health concern and a cause of poor performance in the equine athlete," reports Howard H. Erickson, DVM, PhD, professor of physiology at KSU. "Preliminary results indicate that DHA alone does not reduce pulmonary inflammation or the amount of EIPH."
The group is doing a follow-up study on DHA/ eicosapentaenoic acid (EPA) combination supplementation and its effects in reducing pulmonary inflammation, EIPH, and joint inflammation.
States co-investigator J. Ernest Minton, PhD, "We think the scientific basis to hypothesize that omega-3 fatty acids can control inflammatory processes in the horse are sound. However, the levels of daily intake of omega-3 fatty acids and whether the ratio of omega-3 to omega-6 is an important consideration to affect various inflammatory conditions in the horse remain to be defined."
Doug Herthel, DVM, owner of Alamo Pintado Equine Medical Center in Los Olivos, Calif., and founder of Platinum Performance supplements for humans and animals, says preliminary results from his studies showed that horses fed an omega-3 formula and hay had "significantly lower levels of inflammatory markers" than horses consuming a hay and mixed grain diet.
At Texas A&M, notes Pagan, horses supplemented with soy oil versus corn oil experienced a reduced inflammatory response to a bout of exercise.
Red Blood Cells
Scientists from Southern Illinois University Carbondale confirmed that increased levels of omega-3 fatty acids lead to increased levels in blood plasma and red blood cells.
"We found that the specific omega-3 fatty acids that are the most beneficial to health did get into the red blood cells, and their concentrations were roughly equivalent to the amount the horses were eating—the more they ate, the higher the concentration," writes investigator Sheryl S. King, PhD, professor of animal food science and nutrition, in the Southern Illinois University Carbondale News. "It did take a very long time for the concentration to increase. We didn't actually see it (in blood) until after we had stopped feeding the product, but it stayed around much longer there (59 days after stopping supplementation) than it did in the plasma."
Preliminary results from Herthel's recent studies on his Platinum Performance Equine showed supplementation increased omega-3 content by 78% and decreased omega-6 by 40% in red blood cells after six weeks of supplementation.
"The ability to change the membranes (which control transport of materials from one side of the cell to the other) is useful in decreasing inflammation in general," he notes.
Studies at Texas A&M, the University of Arizona, and Colorado State University (CSU) examined effects of DHA on sperm output and semen quality.
"Each study showed the same trend, although each study showed a slightly different effect," notes CSU researcher Ed Squires, PhD, honorary Dipl. ACT. "Our study showed an increase in the total number of motile sperm using Magnitude, a pelleted, top-dressed product manufactured by United Bionutrition and distributed by Bioniche Animal Health. We evaluated fresh, cooled, and frozen semen, as did the other studies; we saw a major effect on fresh semen and 24-hour cooled semen. For horses that have semen that might not cool very well, there's no question that they're feeding it helps during the cooling process.
"One study even showed an increase in the percentage of morphologically normal sperm and an increase in the concentration of the semen. Omega-3 fatty acids have the potential to affect not only sperm quality, but sperm quantity," he adds.
Mares and Foals
Can the fatty acid composition of a broodmare's diet affect the fatty acid composition of her milk and the fatty acids passed along to the foal? If so, can increased levels of omega-3 convey extra immunity to the foal? The answers, respectively, are yes and maybe.
In separate trials at the University of Florida, Warren found that:
- From foaling through 16 weeks post-foaling, mares fed a control diet (no fat supplementation), corn oil supplements (rich in omega-6), or a 50/50 mix of corn and linseed oil (rich in omega-3) passed along fatty acid levels in their milk and plasma reflective of omega-3 and -6 levels they consumed.
- Beginning one month prior to foaling and continuing 12 weeks post-foaling, mares receiving no additional omega-3, those supplemented with milled flax (rich in the omega-3 fatty acid alpha-linolenic acid), or mares receiving fish oil (rich in the omega-3 fatty acids EPA and DHA) saw similar results as above. Mares and foals fed fish oil produced an earlier inflammatory response than the other two groups, suggesting that omega-3 could confer an early advantage in responding to infection, although omega-3 supplements had no effect on the antibody content of mare colostrum, milk, and foal serum.
- A study similar to the above (fish oil vs. milled flax vs no supplementation) in yearlings found no differences in immune function or inflammation among the groups, except for an earlier inflammatory response in yearlings that had been fed fish oil. However, because all of the yearlings were on fresh pasture, total amounts of omega-3 might not have been very different. "That suggests we can't ignore what forage provides," Warren notes.
Researchers at Kansas State conducted similar studies, likewise finding that omega-3 supplementation of broodmares change the levels of fatty acids in milk and in utero.
Studies on immunity levels in foals from omega-3-supplemented broodmares showed higher immunity levels in the milk, but no increase in blood samples from the foals, says KSU researcher Joann Kouba, PhD, horse teaching and research specialist. There were no foal height or weight differences in foals from supplemented or control mares.
"The jury is still out, because a follow-up study did not find significant differences in milk IgG levels," Kouba says.
On the Horizon
Kouba is now focusing on reproductive function, particularly estrous cycle characteristics, between mares eating omega-3 supplements versus those fed a normal horse diet that's richer in omega-6.
"It's an interesting area because of the connection between omega-3 and prostaglandin levels," she says. "There may or may not be a connection in terms of reproductive function." Results are expected to be made public soon.
Also nearing completion is an investigation by Warren concerning antioxidant effects of omega-3: Does adding more omega-3 fat to the horse's diet increase the production of free radicals, thereby increasing their need for antioxidants like vitamin E? Or do omega-3 fatty acids actually have antioxidant properties of their own?
Despite the hype and tantalizing promises of varied products, there are still many facts yet to be gathered concerning the role of omega-3 fatty acids in the equine diet. Stay tuned for further developments!
QUICK FACTS: ESSENTIAL FATTY ACIDS
Essential fatty acids (EFA) are polyunsaturated fats needed for various metabolic processes. The body does not produce EFA, they are provided through the diet.
"Alpha-linolenic and linoleic acid are both EFAs," explains Lori K. Warren, PhD, assistant professor of equine nutrition at the University of Florida. "Alpha-linolenic acid is the parent fatty acid in the omega-3 family, whereas linoleic acid is the parent in the omega-6 family. Other ‘child' omega-3 and omega-6 fatty acids can be derived from the parents, including EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) from alpha-linolenic acid, and arachidonic acid from linoleic acid. It is these fatty acids that have the greatest biological activity in the body."
"Omega-3 fatty acids are found in highest concentration in marine (fish) oils and in linseed/flax," says Ray Geor, BVSc, MVSc, PhD, Dipl. ACVIM, professor and Paul Mellon Distinguished Chair at Middleburg Agricultural Research and Extension Center, Virginia Polytechnic and State University.
Other sources contain omega-3 in varying amounts, reports Mary Beth Gordon, PhD, regional veterinary nutritionist at Land O'Lakes, Purina Mills LLC. Those include canola oil, soybean oil, walnut oil, walnuts, mustard oil, tofu, and fish (herring, salmon, oysters, trout, tuna, crab, etc.). "Omega-6 is found in varying amounts in borage oil, corn oil, cottonseed oil, grapeseed oil, peanut oil, primrose oil, safflower oil, sesame oil, soybean oil, sunflower oil, pine nuts, and brazil nuts," says Gordon.
Although hay and pasture forages are low in total fat content, most of the fat is made up of omega-3 fatty acids. In contrast, cereal grains such as oats and corn offer primarily omega-6 fatty acids.
Effects of Ratios
"There has been considerable work in other animal species and in humans to show that omega-3 supplementation affects the ratio of omega-3:omega-6 in blood and in tissues, with alterations in the fatty acid composition of plasma (cell) membranes," says Geor. "This effect is most evident when fish oil is fed. This change in composition alters the responses of cells under stress conditions such as an inflammatory insult, with the result being a moderated inflammatory response when compared to non-supplemented animals."
What this Means
"Actions produced by omega-3 fatty acids in lab animals, humans, and other species demonstrate a decreased inflammatory response and are said to improve osteoarthritis and bone formation, reduce allergic hyperactivity, and reduce exercise-induced bronchial constriction," states Joe Pagan, PhD, president of Kentucky Equine Research. "The actions produced from the omega-6 are just the opposite; they increase the inflammatory response, increase allergic hyperactivity, and increase exercise-induced bronchial constriction."
These ideas have been pursued in horse studies. "There is evidence that supplementation with linseed or fish oils alters fatty acid profiles and the responses of inflammatory cells when they are evaluated ‘in the test tube,' with moderation in production of inflammatory substances by these cells," Geor says.
What You Should Know
"Don't be afraid of omega-6 fatty acids because they are essential, necessary nutrients," states Warren. "Some inflammation, which is supported by omega-6, is needed to fight infection and heal tissues. It's when the body goes overboard that we are concerned. "We don't know enough about omega-6 in horses to condemn it. In fact, many of the scary references to omega-6 come from the human perspective."
The average human diet consists of about 30% fat, contrasting with the average horse diet (even fat-added diet) of about 5% fat.
"Horses just don't consume the same kind of diet as humans, so the impact of omega-6 might not be as great in horses, especially when we're talking about negative impact. That being said, we are trying to find out if we need to modify some of the fats we are adding to the horse's diet to make sure we're not causing problems--unknowingly causing inflammation," says Warren.
"Evidence is lacking that supplementation is effective in the prevention or control of disease conditions in horses or in the management of athletic or old horses," Geor notes. "People need to be realistic with expectations. There also is little information concerning the ‘dose' of omega-3 needed for any potential benefit."
Adds Gordon, "Although some horses may benefit from fatty acid supplementation, there is not sufficient evidence at this time to support the statement that every horse needs it. If a horse is receiving access to quality forage and balanced concentrated feedstuffs, then he may not need additional fatty acids." --Marcia King
About the Author
Marcia King is an award-winning freelance writer based in Ohio who specializes in equine, canine, and feline veterinary topics. She's schooled in hunt seat, dressage, and Western pleasure.
POLL: Rehabbing the Injured Horse