Should you feed soya to your horse?

If you keep your horse barefoot, or are thinking about it, you’re probably aware of the importance of diet when it comes to keeping hooves healthy. Start researching what food is ‘good’ and ‘bad’ for hooves and you’ll likely have fallen down a rabbit hole of information. Every blog, news article and forum post has lists of things you should absolutely definitely feed and things you should absolutely definitely not feed, and most foods appear on both lists. It’s no wonder that it gets confusing!

This is the start of a series in which I take a closer look at a food that is considered ‘good’ or ‘bad’ and explain why we think this. Today’s post is about soya. I’m not going to say whether or not you should definitely feed your horse the food, because it’s never that simple and I’m not a nutritionist. The primary sources for the following information are scientific studies and medical websites.

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First on my list is soya. It’s a controversial feed for barefoot horses for a number of reasons, but should we really be worried?

So what even is soya?

Soya, or soybean, is an East Asian legume and one of the most important crops in the world. Due to its high protein and fat content, it’s a staple part of the diet in many cultures and is found in a huge variety of animal feeds. From reading various discussions and articles, it seems that there are three main reasons why soya as a nutrient is so controversial: the high quantities of Omega-6 fatty acids it contains, the phytoestrogens in it, and the potential it has to cause allergies.

Omega-6 fatty acids

Raw soybeans contain about 20% fat per 100g, the vast majority of which is unsaturated. The particular fats we’re interested in are two types of polyunsaturated fatty acid: Omega-3 and Omega-6. These are both known as essential fatty acids because they cannot be synthesised by animals and they perform vital functions in the body. Omega-3 fatty acids are used in normal metabolism, while Omega-6 fatty acids promote growth and cell repair and halt cell damage.

You may well have heard that too much Omega-6 in your diet is bad. This is because some of the Omega-6 fatty acids you consume are turned into a prostaglandin which is linked to inflammation. You often hear that Omega-6 is inflammatory while Omega-3 is anti-inflammatory: this is not actually true. Omega-3 fatty acids do the same thing as Omega-6 fatty acids but at a much slower rate, and both types of fatty acids compete with each other for the enzymes that catabolise (or drive) this reaction. Western diets (for humans) are often much higher in Omega-6 than Omega-3 than the diets of humans thousands of years ago, so the potential for inflammatory effects is increased in many people today.

Different foods contain different ratios of Omega-3 to Omega-6, and it’s important to find the right balance when feeding your horse. We still don’t know what the ideal ratio of Omega-6 to Omega-3 should be for a horse, but it’s likely to be around 1:2.5 to 1:5. This means that if you’re feeding soya, you should ensure that there’s a feed that provides plenty of Omega-3 fatty acids as well, because soya has an Omega-6 to Omega-3 ratio of around 7:1. This is one of the lower ratios out there; for context, corn oil has a ratio of 46:1 and carrots have a ratio of 57:1.

It’s important not to get too hung up on the Omega-6 to Omega-3 ratios of different feeds though, because you can balance it out by giving your horse access to feeds that are higher in Omega-3 as well. The ratios in individual foods are less important than the total quantities of Omega-3 and Omega-6 in the diet.

One of the most straightforward ways to give your horse plenty of Omega-3 is simply to increase their turnout, as most grasses contain higher levels of Omega-3 than Omega-6. If access to grazing is restricted, one possible supplement is linseed (also known as flaxseed), which contains some of the highest amounts of Omega-3 for its volume.

Phytoestrogens

Next up: phytoestrogens. The main concerns people often have about phytoestrogens are that they might cause cancer and that they have a feminising effect on males.  Phytoestrogens from plants are similar to animal oestrogens but they don’t always behave in exactly the same way. Scientific opinion is still divided over whether or not the potential negatives of phytoestrogens outweigh the potential benefits.  Some studies show phytoestrogens to be beneficial for conditions like osteoporosis and reducing the risk of some cancers, others say that the effects are erratic and not easily replicable. The majority of studies into the effects of phytoestrogens on horses have been on mares and the impact on reproduction, rather than on the impact on general riding horses.

I can’t give a definitive answer on whether or not we should avoid feeding horses foods containing phytoestrogens, but I will say this: many of the things we feed horses contain relatively high levels of phytoestrogens, including linseed, apples, carrots, alfalfa, mint and red clover. In fact, linseed contains the highest total levels of phytoestrogens. If you feed any of these and haven’t noticed any dramatic issues, your horse is most likely to be fine with the phytoestrogen content in their diet currently.  Red clover, for example, is a common crop in pastures and grazing land and is said to ease the symptoms of menopause, although a study testing this found that it has no effects whatsoever.

This all suggests that, as phytoestrogens have a much weaker effect on animals than oestrogens, it’s probably fine to feed soya to most horses.

Isn’t soya allergenic?

Another argument against soya (which apparently just can’t catch a break) is that it is an allergen and therefore it could be risky to feed as your horse might have an allergic reaction. The worry came about after a number of studies in the 1980s and ’90s suggested that allergic reactions to soybean products were on the increase. However, it’s since been pointed out that many of these studies have had too much emphasis placed on them, most didn’t actually test soya effectively and that soya is actually less of an allergen than most other allergenic foods. There is always the risk of an allergic reaction, but the chances of it are much slimmer than you might think. Soya products are so ubiquitous now that it’s highly likely your horse has already been exposed to soya in one form or another without you noticing.

 

I’ve tried to answer some of the more frequent questions about soya and how it works. What I hope you’ll take away from this is that you shouldn’t be overly worried about feeding your horse soya, but that it’s also perfectly fine if you decide not to give them soya either. Feeding soya and nothing but soya is probably not the best idea, but it can be a valuable addition to the feed bucket as part of a balanced diet. This is not an exhaustive exploration of soya, so if you have any more questions please feel free to start a conversation below!