Dr Nerida Richards
Equilize Horse Nutrition Pty Ltd
Feed use efficiency is not something that is talked about much in the horse industry. While in the production animal industries, where the amount of feed needed for a measured amount of weight gain or milk or eggs is known and where nutrition is used as an almost exact science to constantly reduce the amount of feed needed for production, in the horse industry, where it is near impossible to measure anything and where our aim is not to produce the most rapid weight gain or the most milk, feed use efficiency is sorely overlooked.
But it shouldn’t be. No, we don’t want our horses growing as quickly as possible. And no, we don’t need our mares producing milk to their maximum capacity. But I am sure not too many people would turn down the opportunity to be able to feed less for the same or better results! And why would you? Not only are you better off economically, but there are a whole host of horse health benefits to feeding more efficiently too. So what is feed use efficiency? And how do we achieve it?
What is feed use efficiency?
We feed our horses to enable them to breed and grow. The more a horse can fully utilise the feed it is fed to achieve the reproductive or growth goals you have set for it, the more efficient it will be. So feed use efficiency is simply a ‘measure’ (and I use that term very loosely as we rarely measure anything in the horse industry) of how fully a horse can utilise the feed it is fed.
How can feed use efficiency be improved?
How efficiently a horse uses the feed it is provided depends both on what is fed and also on how it is fed. Feeding in a way that will allow your horses to fully utilise any pasture that is available to them is also important. Let’s look at the ‘what is fed’ part of the equation first.
The most important things to consider when looking at feed use efficiency from a ‘what is being fed’ perspective are the digestibility of the cereal grains and the quality of protein being fed.
What is fed and its effect on feed use efficiency
Cereal grain digestibility
Cereal grains (predominantly oats, wheat, corn and barley) are fed to horses as a source of calories which then provide the horse with the dietary energy it needs to reproduce, produce milk or grow. A majority of these cereal grain calories are in the form of starch. Starch is simply a whole lot of glucose molecules all joined together.
The most efficient way for a horse to digest starch is to cut it up using enzymes in the small intestine and to absorb it as glucose. But, with the exception of oats, the starch from these grains in their raw or a minimally processed state (minimally processed being things like pelleted and steam rolled grains) is extremely difficult for a horse to chop up into glucose and absorb. So what ends up happening to around 70% of the starch from these grains is it will travel to the horse’s hindgut where it is fermented by the many billions of bacteria in there.
While this fermentation process is a form of digestion, there are two major drawbacks from a feed use efficiency perspective:
1. About 30% of the energy contained in the grain starch being fermented is lost as heat and gas during the bacterial fermentation process. So right off the bat, energy that could have been used to drive reproduction, milk production or growth is simply wasted.
2. There are two main ‘families’ of bacteria in the hindgut, the (good) fibre fermenters and the (not so good) starch fermenters. When raw or minimally process cereal grains are being fed and starch is constantly being delivered to the hindgut, the starch fermenting family literally take over and kill off the ‘good bacteria’ that will happily ferment fibre. SO, you end up with a hindgut that is very good at fermenting starch but very inefficient at fermenting fibre, meaning a large portion of the high fibre forages being fed (pasture, hay and/or chaff) will not be fully digested and yet more energy/calories that were fed to the horse are wasted.
The end result, when raw or minimally processed grains are fed is very poor feed use efficiency, because you are wasting energy from the grains and from the forages being fed.
The solution to this problem is to feed well-cooked cereal grains. Grains that have been well cooked using a combination of heat, moisture and pressure have starch that is very easily chopped up into glucose in the small intestine. This has a double benefit from a feed use efficiency perspective. First, it allows the horse to access close to 100% of the energy contained in the starch and it keeps starch out of the hindgut. Which means the good fibre fermenting bacterial population stays fit and healthy to ferment fibre and extract the maximum amount of energy possible from the forages being fed. It’s a win-win situation and means horses will do so much better on a lot less feed.
% Starch Broken down to Glucose in 15 Minutes In Vitro
I seem to talk a lot about protein quality, and again, it is for good reason. Pregnant and lactating mares and growing horses have reasonably significant protein requirements. But not all protein is created as equal. You see, protein is made from small building blocks called amino acids. There are about 20 of these amino acid building blocks. Some, the horse can make for itself in its body (these are called the ‘non-essential amino acids’) while others the horse cannot make for itself so it needs to eat them in its diet. These ones are called the essential amino acids.
Horses need a very specific combination of amino acids in their diet in order to build muscle and bone or to reproduce and lactate. If they don’t get the right combination of essential amino acids in their diet they are unable to continue with the protein building process and growth rates/muscle development will slow in young horses, while broodmares will begin to ‘mine’ their own body reserves to provide for their foal resulting in noticeable losses of their topline muscle.
Imagine for example you were asked to build a tower out of blue, yellow, green and red bricks, but the tower needed to be in the very specific colour pattern of blue, red, yellow, green, blue, red, yellow, green etc. If you were to begin building this tower, but only got about half the way to the top and ran out of yellow bricks, construction would need to stop, because you absolutely must keep the right colour combinations. This is exactly the same as what happens during the protein building process in the horse. If a horse runs out of one of the essential amino acids, lysine for example, construction of any protein containing that amino acid must stop until more lysine becomes available.
How does all of this relate to feed use efficiency? Well, imagine you have a choice between two feeds, both containing 15% protein, both similarly priced. But one feed contains high quality protein (based on soybean) and is made to a set recipe (so this high quality protein will never be exchanged for a lower quality, less expensive protein) while the other contains ‘vegetable protein’ of unknown quality because it is made using a least cost mixed formula where the cheapest ingredients available at the time are used to make the feed.
The feed containing the high quality protein will be used very efficiently by the horse because the amino acids in the protein it contains closely match the amino acids required by the horse. The feed containing the low quality protein will be used inefficiently because a lot of the amino acids it contains are either indigestible and therefore will pass right through the horse without ever being absorbed, or it will contain too many of some amino acids and not enough of others so protein building processes like muscle and bone development have to stop but the horse still needs to do something with the excess amino acids it has – so it ends up chopping them up and burning them like a carbohydrate as a source of calories. While protein can be used for energy, it was once described to me as being ‘like using twenty dollar bills to start a fire instead of newspaper, it works, but it’s a bloody expensive way to do it’.
Take home message here is if you want a feed that will be used efficiently, look for one that clearly specifies the ingredients used to make it and look for high quality protein sources like soybean and avoid feeds that list ‘vegetable protein meal’ as an ingredient.
How you feed and its effect on feed use efficiency
The second part of the feed use efficiency equation is how you feed. Meal size and the quantity you feed are the most important aspects to consider when trying to maximise feed use efficiency.
Meal size and quantity fed
The digestion of feed is a relatively slow process. The longer you can give a horse to ‘chop up’ its food in the small intestine, and the longer you can let a horse retain feed in its hindgut the more fully a horse will digest that feed and therefore the more efficiently it will be used.
Consider this, a horse has a very small stomach, relative to its size. One of the stomach’s main jobs is to hang onto feed and release it slowly into the small intestine to try and keep the passage rate of feed through the small intestine as slow as possible to allow as much digestion of starch, fats and protein as possible. If you feed more ‘grain-based’ feed (pellets, cubes, sweetfeeds) than a horse’s stomach can physically hold, the excess feed being swallowed simply forces food being held in the stomach out of the stomach at the same rate it is being swallowed. So if you feed in large meals, the feed will travel very quickly through the small intestine and the horse simply won’t get a chance to digest the starch, fats and proteins in the feed. What is left undigested will then be dumped in the hindgut to be fermented and again you have a situation where you are wasting energy (and also protein).
The other trap some people fall into is feeding too much hay. High fibre forages like hay need to linger in the hindgut for quite a while (24 hours or more) to be fully digested. If too much hay is fed, this will force feed very quickly into and then back out of the hindgut meaning the bacteria simply don’t have enough time to fully ferment the fibre and the horse misses the chance to extract a lot of the calories in the hay.
By feeding meals that are too big or simply feeding too much, all you really achieve is a very expensive and highly inefficient feeding program.
Fully Utilise Your Pasture
The last little piece to this feed efficiency puzzle is to feed in such a way that your horses will fully utilise the pasture resources you have available. Pasture is your most economical source of calories and protein for your horses. One huge benefit of feeding a high quality feed (one that is highly digestible and contains high quality protein) is that you can feed smaller amounts. When you feed smaller amounts you leave more room in the gut, more time and more motivation for your horses to actually go and graze.
Let’s take a look at an example using two feeds. The first a fully extruded, highly digestible feed and the second a pelleted feed that is not as digestible and has a lower energy content. Both feeds contain high quality protein from soybean so from this perspective they don’t differ. The extruded feed contains around 14 MJ of digestible energy per kg, the pelleted feed contains around 12 MJ of digestible energy per kg.
Let’s take the case of a pregnant mare who has access to average quality pasture that contains 7 MJ of digestible energy per kg and will eat approximately 11 kg of total ‘feed’, including pasture per day. In mid to late pregnancy her daily ‘energy’ requirements will be around 90 MJ/day.
The table below shows that feeding 2 kg of the extruded feed allows the horse to eat more pasture and consume the same daily energy intake as a mare fed 3 kg of the pelleted feed.
On the surface this may appear to be a ‘sounds good in theory’ concept, but I have seen it work enough times in many different situations to be confident in saying it works very well in practice too. So next time you are presented with feed choices, don’t just look at the price per kg of a product; also consider how efficiently a feed will be used by looking at its expected digestibility and also its protein quality. These factors will determine its daily feeding rate and therefore its total cost per day.
By thinking about how ‘what you feed’ and the ‘way you feed it’ may be affecting feed use efficiency you can potentially improve horse health and reduce overall feeding costs. The key points to consider are feed quality, with well cooked, digestible feeds containing high quality protein offering the most benefit from a feed use efficiency perspective; and how you feed. Feeding in smaller meals will allow a horse to properly digest what is fed and therefore use their feed more efficiently. It will also allow and encourage them to fully utilise the pasture resources you have available.