7 Myths About Feeding Soy

7 Myths About Feeding Soy

It seems that soy is always a heated topic of conversation around the stable yards - some love it, and some hate it! However, there appears to be a lot of misinformation spread via social media and even word of mouth about soy's effects on our horses. So, we have pieced together for you today some myths about soy in the hope that you can make an educated and informed decision about whether it is a suitable feed for your horse. 

1. Myth: Soybean meal contains phytoestrogens, so it is terrible for the health of my horse

Yes, soybeans contain phytoestrogens, but before you say, “Aha, I knew they were bad”, the phytoestrogens found in soy (isoflavones) are so weak that they are doubtful to impact your horse at all. First, let’s take a look at what phytoestrogens are. Put, phytoestrogens are plant-based compounds that mimic estrogen in the body. There are different types of phytoestrogens, which interact differently with the body, and they are found in all kinds of feed, including linseeds, legumes, grains, grass and lucerne! So, our horses consume phytoestrogens daily. The phytoestrogen found in soy is called isoflavones. 

As mentioned above, isoflavones are really weak estrogen-like compounds, so the impact that they may have on a horse is really, really small. To give you an example of how much of a minor impact isoflavones in soybeans may have on your horse, consider this example. Lucerne also contains isoflavones; in particular, it contains coumestrol, which isn’t found in soybeans. Coumestrol has a much more powerful effect on mimicking the biological activity of estrogens when compared to isoflavones in soybeans. Yet, lucerne or alfalfa hay is one of the most common feeds fed to horses worldwide! 

If you are still worried about phytoestrogens in soybean meal, then maybe start with soybean hulls, as these have significantly less phytoestrogens when compared to the meal or bean. 

2. Myth: Soybean will affect the fertility of my breeding mare or stallion

This myth came about due to the phytoestrogen compounds contained within soybean meal. We now know that soybean meal contains a relatively low amount of phytoestrogen to have any significant impact on the horse. Some studies have shown phytoestrogens being detected in mare serum after being fed a soy-based diet, which included Bermuda grass. However, currently, no data exists to show any detrimental effects of phytoestrogens on a stallion or mare fertility.

3. Myth: Horses are allergic to soy

Horses, like people, develop allergies, and like people, some are allergic to soy. But it is estimated that only a tiny percentage of horses are allergic to soy. If your horse is allergic to soybean, you may notice symptoms such as digestive upsets, itchiness, colic, and behavioural and respiratory issues. If you suspect your horse is allergic to soy, it is best to contact your vet for advice. 

4. Myth: Soybeans are toxic for horses

This myth came about from the trypsin inhibitor found in soy. Trypsin is an enzyme found within an animal that helps to break down protein so it can be absorbed into the body. Soybean contains a trypsin inhibitor, which means that in its unprocessed state, soybean inhibits the release of trypsin in the intestine, which affects the way protein is broken down, resulting in a lot of the amino acids not being absorbed by the body. To remove or break down the trypsin inhibitor in soybean, it is heat treated, which can be achieved by either roasting, toasting or extruding. So, if soybeans are adequately treated with the right amount of heat and time, then the trypsin inhibitor factor is removed, preserving the quality of the protein found in soybean. 

5. Myth: Soybeans contribute to muscle wastage of the horse

This myth comes back to the trypsin inhibitor found in soybeans. To reiterate, soybeans fed to horses are heat treated to remove the trypsin inhibitor. This means the protein can be fully absorbed by the body and utilised correctly. In actual fact, soybeans are an awesome source of protein and can be very beneficial to your horse (keep reading to find out why!).

6. Myth: Soybeans add no nutritional benefit to the horse

Soybean is a fantastic source of good-quality protein. Did you know that soybeans are a complete protein? This means that they contain all nine essential amino acids. It is an excellent source of lysine (which helps to build muscle), but it does have lower levels of methionine (helpful for strong hooves). Whole soybeans are also relatively high in oil, about 15-20%, so when you buy full-fat soybean meal, you are getting a high-fat, high-energy feed, which is great for young or growing horses. In addition, soybean hulls, which are only the outer husk of the soybean, are an excellent fibre source for horses (think, super fibre!) because they contain low levels of lignin. So, it is a great feed for a horse that needs a low starch, low sugar, high fibre diet!

Many feed manufacturers use soybeans in different ways. Full-fat soy meal is an excellent product for competition and growing horses or for those that need a little help in the weight gain department, whilst the soybean husks are more suitable for horses that need a low sugar and low starch diet. 

7. Myth: Soybeans are inflammatory

This myth came about due to the higher Omega 6 to Omega 3 ratio of soybeans. Yes, soybeans are indeed higher in Omega 6 fatty acids, and a diet high in Omega 6 fatty acids is known to promote inflammation. So if you do feed soybeans to your horse, then it is best to balance your horse’s diet so that you have the correct Omega 6 to Omega 3 ratio. If you buy a commercially prepared feed containing soybean meal, these feeds will usually be appropriately balanced for your horse, but if in doubt, contact the feed manufacturer!

There are so many great soybean feeds on the market. Some manufacturers will use soybeans in conjunction with other legumes, such as lupins, within their feed, whilst others manufacture a feed based on soybean meal or hulls alone. There is also the possibility to purchase full-fat soya bean meal on its own, with no other ingredients added. Some of our best-selling soybean products include (in no particular order!):

• Benchmark Horse Feeds - Perfect Mash, Super Fibre Mash
• Maxisoy
• Prydes EasiFeed ProteinPak and EasiKeeper
• Hygain Balanced and Tru Care

As always, we are here to help! If you have any questions or want us to source products for you, please visit us online or in-store!