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Are Soybean Hulls Safe For Horses?

Are your soybean hulls safe? Because some of them definitely are NOT!

I love soybean! The protein is amazing and year in, year out we feed it to horses with stunning results in muscle, bone quality and milk production.

BUT… it MUST, MUST, MUST be heat treated correctly to make it safe to feed!

Why Must Soybean Be Cooked Before It’s Fed To Horses?

Uncooked soybean has a few anti-nutritional factors. The most significant one is trypsin inhibitor. Trypsin is a protein-digesting enzyme made by your horse. Your horse uses trypsin to cut up protein into amino acids so they can be absorbed.

Trypsin is like a little pair of scissors whose only job is to cut up (i.e. digest) protein. The trypsin inhibitor in soybean effectively ties a piece of string around the end of these protein-digesting scissors so they can no longer cut any protein up.

The end result… decreased protein digestion! So you can be feeding plenty of protein but if any soybean products you are feeding have active trypsin inhibitor, protein digestion will be reduced! A lot! And the problem is it reduces protein digestion from ALL protein in the diet, not just from the ingredient containing the trypsin inhibitor (i.e. the soybean hulls).

How To Know If Your Soybean Product Is Safe For Horses

I recently picked up two samples of soybean hulls from a large riding horse stable. The horses in the stable were being fed two different brands of soybean hull. The stable manager had gone to long lengths to balance these diets using FeedXL. To look at the diets on paper I expected lovely, rounded, well-conditioned horses.

But they weren’t. The horses being fed the most feed had little muscle. Spines were tent-shaped, rumps were flat and shoulders and chests thin and narrow. I was scratching my head. Something was wrong but I couldn’t quite put my finger on what… until I tested the soybean hulls!

Using a rapid colour test to check for likely active trypsin inhibitor, I tested them to make sure they had been heat-treated enough to destroy all trace of trypsin inhibitor. When heat treatment has been done well, the samples tested should show no trace of a colour change. If heat treatment was not done properly, and active trypsin inhibitor is still present, the sample turns pink. How pink determines how active the trypsin inhibitor will still be… more pink = more active trypsin inhibitor (which is not what we want to see).

And the results, to be honest, are scary! The hulls in the photo at the front lit up like a Christmas tree! Bright pink everywhere indicating lots of active trypsin inhibitor. These ones I suspect have received no heat treatment at all and are totally unsuitable for horses. Yet they were packaged and sold specifically for horses.

The ones in the back, you could see had received enough heat on the outside of the pellet to deactivate the trypsin inhibitor. BUT inside the pellets there was still pink indicating active trypsin inhibitor.

I called the stable feeding these and told them to stop feeding the first pellet immediately. No wonder their horses had no muscle! This product, which they had been feeding for close to 8 months, would have been stopping a lot of protein digestion. And this is not theory… you could SEE how much these horses were deficient in protein, despite their diet containing plenty of it.

The second pellet (in the back) I personally wouldn’t feed either. It will put your horse in a bit of a two steps forward, one or two steps back situation… helping with energy intake but partially blocking protein digestion.

When soybean is PROPERLY cooked, there should be ZERO trace of pink, as shown in the sample on the right here of well extruded full fat soybean. The sample on the left is raw, ground full fat soybean. It is, of course, bright pink… just to show how much the bean itself reacts with this colour test BEFORE it is cooked.

THIS extruded soybean (on the right) is how ALL soybean products SHOULD and in fact MUST look to be safe to feed to horses.

By now, if you are feeding soybean hulls you may be feeling a bit anxious…  wondering if the brand you are feeding is OK or not… it might be, but it may not be either.

How To Test For Trypsin Inhibitor in Soybean

And it is a little bit hard to advise you on what you should do. First step is probably to contact your soybean hulls supplier and ask them to provide any photos they may have of this quick color test check for trypsin inhibitor. Or for a lab analysis for likely trypsin inhibitor activity.

If you are in Australia, Symbio Labs in Brisbane (https://www.symbiolabs.com.au/) can test soybean hulls for you to show you if they have been heat treated enough to be safe to feed.

If you are in North America, you can order a test kit and test your soybean products yourself (https://canadianbio.com/Store) or we can ask around some laboratories for you to see who tests for trypsin inhibitor activity.

If you are elsewhere in the world please get in touch with a local feed or food testing laboratory and ask if they are able to assess soybean hulls for trypsin inhibitor activity.

Unfortunately yet another case of buyer beware. I have contacted the manufacturers of both of these products. Hopefully they will begin to heat treat their products correctly AND take a much more active role in testing products properly before selling them.

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5 Ways One Balanced Diet Can Be Better Than Another

We recently had a member of our nutrition forum ask ‘Can one balanced diet be better than another, or is the key point that it is balanced?’

This is probably the best question I have ever been asked! And the answer is absolutely YES! One balanced diet can be better than another!

BUT, before I explain why, I just want to say that diets balanced using FeedXL will be 1000 (or more) times better than a diet that is unbalanced and not meeting a horse’s basic nutrient requirements. So take heart that if your diet is balanced on FeedXL, you are way ahead in keeping your horse healthy.

So balanced diets that meet all of your horse’s known nutrient requirements are better than unbalanced diets that do not meet requirements.

But, one balanced diet can certainly be better than another.

Here are 5 examples of what makes one diet better than another:

 

Factor OK Option Better Option Why is this better?
Forage Amount Diet just meets the FeedXL minimum forage requirement. Forage is a major component of the diet and is used to meet as much of a horse’s daily digestible energy requirement as possible. The more forage in a diet the better your horse’s gut health will be. If you feed a balanced diet but your horse’s gut is unhealthy, your horse’s overall health will be limited.
Forage Variety You feed only one or two different types of forage. For example Teff hay and alfalfa/lucerne chaff or pellets. Your forage (pasture, hay, chaff, forage pellets or cubes) is made up of several different plant species. For example, your pasture has 3 different grass species plus clover, and you feed a mixed meadow hay plus alfalfa/lucerne chaff. While we know a lot about many nutrients a horse needs (like copper, vitamin E etc) there are MANY nutrients (like the omega fatty acids and most of the essential amino acids) that we know your horse needs. We just don’t know how much he needs. Feeding a large variety of forages improves the chances you will meet requirements for all of these nutrients we don’t understand very well yet.
Uncooked Grains The ONLY OK option for uncooked grain is oats. ALL other grains must be cooked. They are definitely not OK to feed uncooked. All grains are easier to digest when they are cooked (boiled, extruded, steam flaked, micronized). In fact you must only feed barley, corn and rice if it has been cooked. Feeding any of these grains uncooked is going to make your horse sick. The starch from cooked grains can be almost fully digested in your horse’s small intestine. Meaning less starch is allowed to get into your horse’s hindgut to feed the ‘bad’ bacteria. If you do feed raw grains, your horse’s hindgut will become acidic, bad bacteria will flourish and your horse’s gut and overall health will suffer.
Using Oil All oils are ‘safe’ and all provide the same amount of digestible energy in a diet. But, some oils like sunflower and corn oil are extremely high in omega 6 and can unbalance your horse’s omega 3 to 6 ratio. Canola oil provides a good blend of omega 3 and 6 fatty acids and is particularly useful in diets that contain no grain to provide the omega 6 your horse will need. Flax/Linseed oil is very high in omega 3 and is super useful in high grain diets to balance the omega 3 to 6 ratio. If you feed too much omega 6 in a diet it can result in excessive inflammation. Choosing your oils to match your diet (a little like choosing your wine to match your meal) means you will meet omega 3 and 6 requirements and keep the ratio between the two balanced.
Protein Quality As long as you meet your horse’s protein AND lysine requirement in FeedXL you will be doing a good job of providing enough protein and essential amino acids. BUT, not all proteins are created equally. Cottonseed meal, for example, contains lysine, but 60% of it is unavailable for absorption. Or flax/linseed meal is high in protein but it is low in essential amino acids. Choose premium quality proteins for your horse’s diet so that when FeedXL shows you that crude protein and lysine requirements are met, you also have an excellent chance of meeting all requirements for the essential amino acids. This includes choosing things like a component of soybean in preference to an unnamed ‘vegetable protein meal’ and/or using some alfalfa/lucerne together with your grassy forages. When you feed better quality protein you will get more muscle! When you are able to use high-quality sources of protein that meet your horse’s essential amino acid requirements you will have a better chance of 1. Providing enough of the amino acid ‘Leucine’ to switch muscle building on; and 2. Providing the building blocks needed to actually build muscle.

 

So if you want the best possible diet, here are my top 5 tips:

  1. Feed as much forage as possible to meet digestible energy requirements.
  2. Use as many different types of forage as possible.
  3. Never feed uncooked grains!
  4. Use oils that have an omega 3 to 6 profile that will complement your horse’s diet; and
  5. Use high quality proteins.

If you can do all of that AND have a balanced diet, your horse will be ready to take on the world!

Understanding Protein Quality in Horse Feed

After energy, protein is the most important nutrient in a horse’s diet. Protein is needed to build good quality hoof, hair, skin, organ tissue, muscles, eyes, blood and bones. Protein is also a crucial part of enzymes and hormones and is an absolutely essential nutrient in a horse’s diet. After water, it’s the most plentiful substance in a horse’s body.

But as with many nutrients, ‘proteins ain’t proteins’. Some protein is of very high quality, other proteins can be so low in quality that they will seriously limit a horse’s ability to grow, reproduce, perform or build muscle. So what determines protein quality? First, let’s look at what proteins are.

What is protein?

Proteins are long chains of small molecules called amino acids. As a good analogy, think of amino acids as train carriages that join together with other amino acids to form a protein ‘train’. Amino acids, and therefore proteins, are organic compounds containing carbon, oxygen, hydrogen, nitrogen and sulphur.

The Amino Acid Puzzle

There are 21 amino acids which can be joined together in almost limitless combinations to form proteins. Up to 12 of these amino acids can be manufactured by the horse in its body, so they are known as non-essential amino acids. Under certain conditions like growth or illness, six of these non-essential amino acids must also be supplied in the diet. These ones are therefore known as ‘conditionally essential amino acids’. The remaining 9 amino acids are termed ESSENTIAL amino acids. These essential amino acids cannot be manufactured by the horse and must be supplied by the diet.

The 3 most limiting amino acids in the equine diet (meaning the amino acids that are likely to become deficient first and limit the horse’s ability to grow, reproduce, perform or build muscle) are lysine, threonine and methionine.

Protein quality

While it is possible, and even likely that horses do absorb some very high quality bacterial protein from their hindgut, a majority of a horse’s protein needs are met by what is fed in the diet. So the quality of protein you feed is extremely important.

Protein quality is determined by how well a particular protein meets a horse’s requirement for amino acids, and particularly the essential amino acids. In other words, a high quality protein will contain amino acids in very similar proportions to the amino acids a horse needs. Low quality proteins will either be too low in some of the essential amino acids to meet a horse’s requirement or they will contain essential amino acids that are not available for absorption, again making that protein unable to meet a horse’s requirement.

Selecting quality proteins?

Different feeds contain different levels of the essential amino acids and thus vary in ‘quality’. As a general rule, grass hay and pasture contains lower quality protein than legume hay and pasture like lucerne/alfalfa and clover. C4 type grasses also contain lower quality protein than C3 type grasses.

Cereal grains like oats, corn and barley contain lower quality protein than legumes such as soybean, lupins and beans. Co-products like copra meal sit in the middle with lower quality protein than legumes, but better quality protein than cereal grains. Of the commonly used protein ingredients in horse feed, heat treated cottonseed meal contains the lowest quality protein of all. Soybean contains the highest concentrations and best combination of many of the essential amino acids and is thus touted as the best quality vegetable protein available.

The absolute Rolls Royce of protein quality is whey protein. It has exceptionally high levels of essential amino acids that match almost perfectly a horse’s needs for protein. Just a small note of caution, if you wish to use whey protein in your horse’s diet, be sure to purchase ‘whey protein concentrate’ and not ‘whey powder’. Whey powder is only about 13% protein and contains over 50% lactose, making it unsuitable for use in equine rations.

Which horses need high quality protein?

Not all horses need very high quality protein in their diet. Dry or early pregnant mares and horses in good condition that are either not in work or only in light work have only moderate to low protein requirements that are generally easily met by average to good quality grass pasture and/or hay.

Growing horses, late pregnant and lactating mares, performance horses and any horse needing to build and maintain muscle mass do require high quality protein in their diet. These classes of horse will not do as well as they could unless high quality protein is supplied in the diet. Grass pasture or hay based diets will generally need to be supplemented with some legume hay or grain for the best results. This is why adding lucerne/alfalfa hay to the diet of horses needing to gain weight is recommended (see Newsletter #6 – 7 simple steps for putting weight on your horse). The table below shows the % crude protein and g/kg of lysine in some common feed ingredients.

Name Crude Protein (%) Lysine (g/kg)
Whey Protein Concentrate 80 89.8
Soybean Meal 45 30.1
Soybean (Full Fat) 37 23.3
Canola Meal 37 21.1
 Faba (Tick) Beans  24  14.8
 Wheat Germ  23  14.7
 Cottonseed Meal*  36  14.7
 Lupins  28  13.3
 Linseed Meal  32  11.8
 Sunflower Meal  32  11.0
 Linseed  24  9.2
 Copra Meal  21  8.4
 Lucerne Hay  17  8.0
 Rice Bran  14  7.0
Palm Kernel Meal 17 6.4
 Millrun  15  6.3
 Wheat Pollard  14  6.3
 Wheat Bran  14  5.6
 Black Sunflower Seeds  29  5.1
 Soybean Hulls  12  4.7
 Sugarbeet Pulp  9  4.0
 C3 Type Grass Hay  11  3.8
 Barley  10  3.7
 Oaten Hay  8  3.0
 C4 Type Grass Hay  9  2.8
 Oats  8  2.8
 Wheaten Hay  8  2.8
 Corn (Maize)  10  2.8
 Rice (White)  8  2.7
 French White Millet  11  2.1
 Oat Hulls  4  1.8
* Heat treated cottonseed meal appears to have moderate levels of lysine, however during the oil extraction process, a toxic compound called gossypol binds itself to lysine, which means the gossypol is no longer toxic, but it does render the lysine indigestible, so digestible lysine levels are much lower than this.

 

Using FeedXL to monitor protein quality

The FeedXL Pro and Advisor plans include lysine as part of the nutrition analysis of a horse’s diet. Making sure that crude protein as well as lysine requirements are met in a diet will ensure your horse is getting the level of protein quality it needs.

If your diet is low in lysine, this indicates that the overall protein quality of the diet is low. In these situations, your horse’s ability to use the protein in its diet to grow, reproduce, build muscle or perform will be limited, even if crude protein requirements are met in the diet. If your horse’s diet does indicate lysine levels are too low, the following steps to increase lysine are recommended (in order):

  • Substitute some alfalfa/lucerne or clover pasture or hay for grass pasture or hay in the diet, adding up to 1 kg/100 kg of bodyweight (1 lb/100 lb bodyweight). In most cases, you will find this is enough.
  • If you use a complete feed, look for feeds that contain high quality protein legumes or if you mix you own feeds add legume grains like soybean, lupins or faba beans/tick beans/field beans to the diet. Avoid any feeds containing cottonseed meal or unnamed vegetable protein meals.
  • Small amounts of whey protein concentrate (or whey protein based products) can be used. For best effect in working horses, the whey protein should be fed within 15 minutes of the completion of exercise.

Lysine supplements are also available and can be used to boost lysine levels in your horse’s diet. You should however be aware that the level of lysine as shown by FeedXL in your horse’s diet is an indicator for overall protein quality in the diet. Increasing lysine by using legume hays or grains or whey means that along with lysine, you are also adding methionine, threonine and the remaining 6 essential amino acids. Adding purified lysine will certainly fill the specific lysine deficiency, but it may leave your horse with unquantified deficiencies of other essential amino acids.

Take Home Message

When looking at protein in your horse’s diet, always remember ‘proteins ain’t proteins’. Depending on their amino acid composition, some proteins are very high quality with good levels of essential amino acids while others are low in essential amino acids and therefore low in quality. The high quality proteins, including those from legume forages including lucerne/alfalfa and grains like soybean are able to support growth, pregnancy, lactation and muscle building, while low quality proteins like those from cottonseed meal and cereal grains will not be capable of properly supporting horses with large requirements for quality protein.

Not all horses require high quality protein, but if your horse is pregnant, lactating, growing or working hard and needing to build and maintain muscle mass the quality of protein in the diet will play a big role in determining how well your horse ‘performs’. Use FeedXL Pro to keep track of protein quality and to alert you when the diet is deficient.

 

Dr. Nerida Richards is FeedXL’s resident equine nutrition specialist. With a degree in Rural Science, a doctorate degree in equine nutrition and nearly 20 years of full time, on the ground experience in feeding all types of horses Nerida is able to help FeedXL members solve any problem they may come up against with feeding their horses. To learn more about Nerida and to ‘meet’ the rest of the FeedXL team, check out our About Us page here.

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