Can Food Make My Horse Behave Badly?

Excess energy can cause problems

Owners' observations follow references at the end of this article.
Is it possible that your horse doesn’t need a calming supplement or remedial training, but a diet change? Yes, it is! Spring grass and high sugar / high carb feed can cause excitability and unwanted behavior in otherwise well-behaved horses. When the culprit is spring grass, a grazing muzzle might curtail intake enough to restore your horse’s normal good behavior. If the issue isn’t seasonal, a change in feed is worth a try. A horse who needs the calories may behave better when getting those calories from fat instead of carbs or sugar. This is well documented. There is evidence that gluten sensitivity can be responsible for chronic inflammatory small bowel disease. This disorder (particularly observed in dressage and sport horses) is associated with intermittent colic, weight loss, poor performance and anemia. Other potential culprits are less well known, but their impact is reported by some observant owners. These are the legumes soy, clover, and alfalfa or lucerne. One crucial factor seems to be that legumes are high in phytoestrogens, plant based compounds that have effects similar to the hormone estrogen. Soy is especially high in phytoestrogens. This is significant because soy is a staple in horse feeds, as an economical source of protein. Soy and alfalfa are also common ingredients in supplements. Studies of other species (none seem to exist for horses) indicate that phytoestrogens have a positive effect on some individuals, but negative effects on others. Negative behavioral effects reported include aggression and reduction in friendly behaviors toward others. Many horses appear to do well on feeds containing soy, but some owners report significant behavioral impact, especially being spooky and excitable. Since phytoestrogens can influence hormones, is it possible they are at the root of some "marish" behavior? (Related article: Marish Behavior: What Causes It?)

Sometimes the culprit is your horse's feed

When someone says, “There is no evidence that soy impacts a horse’s behavior,” that means they are not aware of any scientific research. I’m not holding my breath waiting for that research. Someone has to pay for it, yet if the outfit paying for a study has a vested interest in the outcome, the results cannot be considered unbiased. That is Research Methods 101. Feed companies, the logical source of funding, have no incentive to demonstrate that soy could be a problem. Alfalfa has also been shown to make some horses “supercharged”. Although it has the benefits of being high in protein, low on the glycemic index, and low in NSC (Non-structural Carbohydrates), it also has the potential to create health problems, especially if it’s a large portion of a horse’s diet. Clover might not provoke behavior issues, but it poses a laminitis risk for insulin resistant horses, in addition to other possible health issues. Another consideration with soy is that soybeans are routinely sprayed with glyphosate (Roundup), especially those that are genetically modified and therefor tolerant to glyphosate. Other feeds, including alfalfa, are often sprayed with glyphosate, though perhaps not as heavily as soybeans. Glyphosate has been shown to have negative impacts on the health of other species, and there is growing suspicion that some horses exhibit a sensitivity to it. Suspected symptoms include ulcers, digestive issues, inflammation, and itchiness. A horse who is physically uncomfortable is not likely to be on his best behavior. The tricky point about feed and behavior is that not all horses react to different feeds in the same way. So if your horse’s behavior is questionable, read your feed tag. If it includes soy and/or alfalfa, swap to something that doesn’t. Watch your horse and see what happens. If you see an improvement in behavior, problem solved! For more information on healthy horse keeping, see these articles Healthy Horse Keeping or Chapter 20 of What Horses Really Want: Unlocking the Secrets to Trust, Cooperation, and Reliability. References and owner observations follow next photo

Sometimes a change in feed means a change in behavior

References:
Effects of Feeding on Behavior of Horses May 25, 2012 By Dr. Joe Pagan https://ker.com/equinews/effects-feeding-behavior-horses/

The pros and cons of phytoestrogens By Heather B. Patisaul and Wendy Jefferson https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074428/

Increased aggressive behavior and decreased affiliative behavior in adult male monkeys after long-term consumption of diets rich in soy protein and isoflavones by Neal G Simon et al. https://www.sciencedirect.com/science/article/abs/pii/S0018506X04000169

Soy Safety: Depends on the Source, Nutritionists Say By Lisa Kemp | Oct 27, 2008 https://thehorse.com/123469/soy-safety-depends-on-the-source-nutritionists-say/

Protein Punch: Soybeans in Horse Feeds September 25, 2015 By Kentucky Equine Research Staff https://ker.com/equinews/protein-punch-soybeans-horse-feeds/

GMO and Glyphosates: What You Need to Know for Your Horse’s Health By Joyce Harman, DVM -November 2, 2019 https://www.horseillustrated.com/gmo-and-glyphosates https://harmanyequine.com/gmo-and-glyphosates/

A RASH OF ROUNDUP: GLYPHOSATE SENSITIVITY IN HORSES BY TIGGER MONTAGUE · MARCH 21, 2016 https://blog.biostarus.com/glyphosate-sensitivity-in-horses/

Lucerne Hay in Equine Diets April 15, 2011 By Dr. Peter Huntington https://ker.com/equinews/lucerne-hay-in-equine-diets1/?highlight=clover

Myths and Truths About Alfalfa Posted on March 1, 2021 by Dr. Kellon https://drkhorsesense.wordpress.com/2021/03/01/myths-and-truths-about-alfalfa/

All About Feeding Horses Alfalfa By Heather Smith Thomas | Mar 11, 2019 https://thehorse.com/110110/all-about-alfalfa/

Possibility of Gluten Sensitivity in Horses Examined by Casie Bazay
https://thehorse.com/117346/possibility-of-gluten-sensitivity-in-horses-examined/

Gluten sensitivity in sport horses
https://www.sciencedaily.com/releases/2012/04/120430100649.htm

Following are observations left as comments in response to a facebook post on food and behavior.: You can email or message me if you have any you would like to add.

We find that over the top mareish behaviour (as well as aggression in geldings) can be caused by feed - legumes such as clover, soy meal or lucerne being top of that list. Remove these from feed/forage and it makes a HUGE difference - I hardly know when my mare is in season.

When I moved mare to her current farm she was a nut that spring and I realized it was becuase she really didn't get grass before and was now in a very lush 8 acre pasture. Cut out her grain, and she was herself again. She also only gets low sugar treats if she gets any (other than the occasional Banana)

I had one horse that turned mean on sweet feed. Changed to pelleted feed and he was a sweetie for all 30 yrs of his life.

My horse needs to never eat grass, he's an absolute tit on it. Also alfalfa and carrots send him nuts. He only needs to sniff a bit of sugar and he's mega spooky

It's a really interesting article. I was advised by a feed rep recently on how good soya is for horse. It just didn't sit with me 100%. I did try it, however, as I'm open to all avenues of thought. She's a very laid-back Clydesdale who struggles to keep her weight on. Her behaviour is noticeably far more fizzy on the soy based feed, so I'm currently swapping her gradually back to her original plan.

I once had a tbxarab, we were advised to give him farriers formula to improve his feet. Sent my boy completely loopy, bucking and rearing in the stable due to massively elevated energy levels. Completely abnormal behaviour for him. Stopped the farriers formula and he returned to his normal calm nature. [Note: Farriers’ Formula is soy based.]

Legumes are so complicated. The higher calcium in alfalfa can help balance stomach PH and balance the Ca:P ratio in growing horses. It is often actually lower in potassium than grass hay making it ideal for HYPP horses. Finding the right diet for your horses is important. What may work for me, might not work for you. Every individual horse in every setting is different.

My big guy (17hand warm blood who I adore) is a NUT case on high sugar foods he does great with alfalfa... He is on a special food that is low in sugar and he does great!!!

Yes! My mare is soy intolerant, and is a spooky, excitable mess when she eats it.

My gelding is the sweetest most gentle guy....unless he gets any kind of sweetfeed, then he's a snarling, ears back monster! I no longer feed any horse any kind of sweetfeed as in my case they don't need it and he obviously reacts badly to it!

Several factors come into play regarding legumes - yes phytoestrogens is part of it but they also contain photodynamic particles which are the main causer of 'sunburn' and also 'mud fever'. Add to that the fact that they are nitrate accumulators and also very high in potassium and you have a perfect storm - especially if fed alongside any green vegetative grass. Nitrates are a huge problem for horses which is only becoming worse. Unlike ruminants which have a rumen inwhich to process nitrates, horses do not and they can not tolerate a diet high in nitrates. We advise avoiding these plants in the horses diet altogether if you can. This means spraying out clover with a broadleaf spray every spring. (This spray also gets rid of catsear) and even though I hate the thought of using any spray, this is the one spray I do use - (rock and a hard place) It also means checking labels on any processed feed to avoid things such as lucerne/alfalfa, soy meal (the hulls are OK), lupin meal. Unfortunately these things have proliferated as people seek to avoid grains. Grains are actually not usually a problem (Unless the horse has EMS or is laminitic) fed in moderation.

Note: I have my pastures sprayed as needed with Cimarron, a broad leaf weed killer. While we avoid chemicals as much as possible on our farm, we decided this was a necessity after Bronzz got laminitis on our clover laced pasture. Unlike Roundup, Cimarron works on an enzyme level to kill only broad leaf plants, and is relatively safe for everything else.