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Sources of Calories and Critical Points

The next thing I want to talk about is the source of calories. How can we get a significant number of calories into the horse and remember they need upwards of 30,000 calories, 30 megacalories, if they are a hard working horse. How do we get these calories into the horse without harming him in any way? One of the main sources of calories is soluble carbohydrates or starch. What would be a feed ingredient that is very high is starch? Corn. What would be a feed ingredient that is high in insoluble carbohydrates or fiber? Hay. We can also add fat to the horses ration. And if there is not enough starch and not enough insoluble carbs present and not enough fat present, the horse will use protein for energy. Or, if there is too much protein in the diet, say they’re on a 100% alfalfa diet, they also will use protein for energy. That is not an ideal scenario, but the horse can do it.

Soluble carbohydrates are the main source of energy for anaerobic metabolism. What is anaerobic metabolism? I am talking about anaerobic-type exercise. What kind of exercise in the horse is anaerobic? What does that mean, anaerobic exercise? Sprinting, anything that has to do with strength, speed or power is anaerobic. Anything that has to do with endurance and low impact exercise is aerobic. And the same is true for horse activities. Activities such as short distance racing, reining, cutting, cow horse, jumping, all of that is anaerobic. To do any of these activities, the horse has to have some starch in the diet. Because starch turns into glycogen and glycogen is the only substrate that will be used for anaerobic activities. If you feed only hay, your horse could not do a high level of anaerobic activity. Starch is highly digestible, and if you remember the first lecture, where in the equine digestive tract is it absorbed, digested and absorbed? In the small intestine. And what happens if it is not all absorbed in the small intestine, is what this guy was saying earlier, it goes into the hindgut and then it is anaerobically fermented and it turns into lactic acid and that is a scenario that you want to avoid in the horse. In other words, you do not want to have a starch overload. But then if we are talking about if we have to get a lot of calories into the horse, if we do that only by feeding corn, we run into trouble because we will have a starch overload. Anyways, up to a certain point, it is highly digestible. The insulin spikes are going to be high. What is insulin? It is a hormone. What does it do? It controls blood sugar. In other words, when blood sugars go up, which it will after a starchy meal, insulin levels go up and that allows for some of that glucose or blood sugar to be deposited into the cells either as glycogen or as fat. When insulin goes up, what you will is, you will see a spirited horse. In other words, that makes your horse kind of hot. That is something you do not want. On the back side of that, your horse is going to be a little bit lethargic. In other words, you are putting a lot of energy into that horse and it is going to release it in a wave-like way. It is not going to be a slow-release, constant form of energy. In other words, you want to reduce the amount of energy coming from starch as much as you can. At the same time, not reducing it enough to where you run into the problem with anaerobic metabolism.

There is some energy that is derived from insoluble carbs, or hay, by the production of volatile fatty acids. Where are volatile fatty acids produced in the horse's digestive tract? They are produced in the cecum and the colon by fermentation. Insoluble carbs can be a pretty good source of energy, if the solubility is a little bit improved. For example, by feeding a little bit of beet pulp, you will improve that solubility of fiber. Beet pulp, basically, is a fiber. But it has a much softer cell wall than some of the other fiber components. Therefore, it’s more soluble and the horse can get a little bit of energy out of beet pulp. Not a whole lot. Not compared to corn. But a little bit. So, it can be an additional source of energy and you can reduce feeding corn a little bit, if you increase your beet pulp, which will result in a healthier gut. The digestibility of fiber is also increased, and I will talk a little bit about that when we talk about feeding fat.

Fat is the primary energy source for aerobic metabolism. Anything that is slow, low impact will burn fat. It will burn very little glucose or glycogen, but it will burn a lot of fat. As long as there is enough fat in the diet and the horse has enough fat on his body, so he is at least a body condition score of five, he will have enough energy for lots of aerobic metabolism. Fat is highly digestible, up to about 12% in the diet. Once it goes beyond that, it is not digestible anymore. It does not cause any changes in insulin, which is a good thing. You do not have a horse that is hot and then lethargic. You have constant this energy release and the horse is going to much more even-keeled throughout the performance. Up to about 12% in the diet. Anymore than that will be, the digestibility of it goes down and it shows by the horse is going to have some diarrhea because some fat is going to go right through him. The fat can also cause a little bit of an increase in the digestibility of fiber. And the way this works is when you add more fat to the diet, automatically you are going to remove something else. Why are you going to remove something else? You are actually not going to remove something else. But what happens is, when the horse eats more fat in the diet, he is going to eat less of the total diet because the diet is going to be more energy dense per unit of weight. One of the things he consumes less of is starch. And if he consumes less starch, less of it will end up in the hind gut where it is not supposed to be. Therefore, the pH in the hind gut is going to stay higher, stay more optimal for fiber fermentation, so you are going to improve your fiber digestibility when you add a little bit of fat to the diet. And that is how that works. Also, you will see an increase in stamina because you are feeding the horse a more energy dense diet. So you are getting more calories into the horse. And therefore he is going to have more stamina. You will see an improvement in the quality of the hair coat and hoof quality. One of the ways you do that is by supplying some essential fatty acids that may otherwise not be in the diet. And also, if you improve the fiber digestion in the hind gut, you are going to improve biotin production, which biotin and other B vitamins are produced in the horse’s cecum. They do not have to be supplied in the diet, as long as the cecum of the horse is working well. And it should be working well if you feed it a pretty good diet. There is no additional B vitamin that needs to be supplied. We also see an improvement in performance when we feed fat of the hard working horse. And there is no direct mechanism for that because the hard working horse does not use fat for its work. It uses glycogen. But we see what we call a glycogen sparing effect. So that means for regular basal metabolic rate, the horse will preferentially use fat instead of glucose. And therefore, save some of the glycogen for the harder work if he is being fed a high fat diet. If you ever take 431 we will into a lot more detail in that too.

Protein, the horse’s requirements for protein increase as the exercise goes up. But the percentage of protein in the diet does not increase. In other words, the protein to calorie ratio does not increase. Protein to calorie ratio is one of the most important concepts when you assemble horse rations. For those of you who were in the academic quadrathalon, that was one of the questions and no one got that one right; because I guess this lecture came a little too late. Protein to calorie ratio may not be as important of a concept in other livestock species, but it is very critical in the horse.

Protein is a metabolically expensive source of energy. What does that mean, metabolically expensive? Basically, what that means is that energy will be used to metabolize protein. Not only that, but there is something on the protein, on the amino acid molecule, that cannot be used for energy. That is nitrogen. Nitrogen will be converted into ammonia and will be excreted through the kidneys. That is an additional part of the metabolism that protein has to go through if it used for energy, but it doesn’t supply that part of the metabolism. Doesn’t supply any additional energy. So it is kind of a waste. If protein is used for a building block and for muscle build, it does not get broke up that way, the nitrogen will be used instead of excreted.

Here the quality of protein or amino acid profile is also a very, very important aspect of the protein story. What is quality of protein, what does that mean? What is a high quality protein versus a low quality protein in your own diet? If you think of your own diet, what would you think is one of the highest quality proteins in your own diet? We’ve talked, I think I mentioned that a little bit last time. What is one of the highest quality proteins? Yes. Red meat would be, because it is very, very similar to your own muscle makeup. So anything you can eat that more closely resembles your own muscle makeup, the higher quality, the higher the biological value of that protein is. Now, horses are vegetarians. So how can we improve their diet to supply higher quality proteins in their diet so that they come at least close to their own biological value of protein. Like I said last time, one of those things is soybean meal. Soybean meal or soy products, in the plant world, are among the highest quality that you can find. They still do not come close to the quality in meat, eggs and milk. But they are fairly high quality for a plant source.

The next thing is the protein to calorie ratio. An adult horse needs about 40 grams of crude protein per megacalorie of digestible energy. That 40 grams, per megacalorie of digestible energy, does not change with exercise. And the reason it does not is because you increase your megacalories in the diet. Therefore, your absolute consumption of protein will also increase. The exception to that is the growing horse and the lactating mare. They need 50 grams of crude protein per megacalorie of digestible energy. And the reason they do is because they put on muscle weight. A growing horse puts on muscle weight. And the lactating brood mare puts about 50% of the protein she consumes directly into the horse’s diet. And some of these I have listed here, Omolene 200, Strategy and Omolene 300, those are feeds that are specifically formulated for that type of horse. What is being kept in mind here is the protein to calorie ratio, because that is really, really important. That is very exact, so there should not be a lot of variation in it at all.

Here is another example of the entire nutrient content of oats versus a feed product like Strategy.

If you look at the protein content, the horse needs about 14% protein in its diet and if you look at oats only supply 10% protein. So, what type of hay would you have to feed with oats in order to make up for that? Yes, you would have to feed some alfalfa and you would be okay there. Oats are actually a pretty good for a grain product. They’re pretty good as far as fat content is concerned, they’re about 4.8%. They are a little bit higher in fiber. They supply about 1,200 calories per pound, 1.2 megacals per pound that would be. What is, if you look at calcium and phosphorous, what is one of the problems with oats? What kind of ratio do you see there? Yes, one to three. And that is backwards. A horse needs anywhere from 1.5 to 1 to 3 to 1 calcium to phosphorus in order for proper bone metabolism and other metabolism. If you feed oats and grass hay, and grass hay usually is about equal in calcium and phosphorous, if you feed oats and grass hay your horse could run into problems pretty quickly. Also, your protein would not be high enough, because most grass hays are anywhere between 7% and 9% protein, so then your overall diet is less than 10% protein and your horse becomes protein deficient. If you feed alfalfa, you’ll be okay. If you feed oats and alfalfa, your protein is adequate and your calcium to phosphorus ratio would be okay as well. Oats and alfalfa are still going to deficient in some of the minerals, especially some of the trace minerals like copper, zinc and selenium. If you look in the other column there, the calcium to phosphorus ratio is corrected for, so it is about a 1.5 to 1 and then all the trace minerals are supplied in a higher ratio as well? If you feed oats, what you have to make sure of is that you supply a high quality trace mineralized salt block and then make sure that your horse consumes enough of it to make up for any of the deficiencies that oats will have.

What is one of the problems when you feed a trace mineralized salt block to the horse? Will the horse eat it, will the horse lick on it, consume it? Some will and some will not. Why would they lick on it, first of all, why would they like it? Some of them may be bored and they start licking on it and they like the salt taste. Horses that are deficient in salt, will have a craving for salt. But they will not have a craving for any of the other minerals. If they are deficient in the other minerals, they will not have a craving for any of the other ones. They only have a craving for salt. Therefore, most of the salt blocks you can buy have other minerals in them, so hopefully if they eat enough salt then they will get enough of the other minerals too. But there is no guarantee of that. But if you feed a feed that already has the trace minerals in the feed, and they just like the feed because that is what they eat everyday, then you can make sure that way that they will have enough of the trace minerals in there and you do not have to worry about a salt block. The only time you really, really a salt block in addition then is in the summer time when you ride them hard and they sweat a lot because then they will lose a lot of salt through the sweat. But, even then horses get really efficient at not sweating salt, if the diet may be a little bit low in salt. They get more and more to where they basically just sweat water and a lot less salt.

Summary here is the critical points are most importantly calcium to phosphorus ratio Should be 2 to 1. Anywhere from 1.5 to 1, to 3 to 1 is okay. In the adult horse, it can get higher than 3 to 1 and you would still be okay, it can be 4 or 5 to 1 and you would still be okay. In the growing horse, that is not a good idea. And so if you feed high quality alfalfa to the growing horse, you should feed some grass hay as well because some of the high quality alfalfa is as high as 8 to 1 it has so much calcium in it. And that is not a good idea for the growing horse. But the adult horse does not really have a problem with it.

The next thing is a variety of caloric sources; you do not want to supply all of the calories with starch. If you do that, you will have a starch overload real easy. You want to spread that out over starch, fat, fiber and a little bit of protein. When I say a little bit of protein, I mean a little bit of protein for energy. Not a lot of protein for energy. Protein should only be, or primarily be, for muscle build and muscle rebuilding. But a little bit of it is okay if it is used for energy.

Performance horses do the best between 6% and 8% fat in their diet. If you feed more than 8% fat to performance horses, it is okay if they are primarily aerobic performers. In other words, for the endurance horse, anything over a medium distance race horse, trail horse, pleasure horse to feed a little bit more than 8% fat is okay. If you feed more than 8% fat to the anaerobic performer, they may not eat enough of the diet to get enough starch. They need a little more starch, they need a little more starch. Otherwise, they will not have the glycogen available to them to do that anaerobic work that we ask them to do.

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