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Energy

I am going to start with energy. It is technically not a nutrient. It is a property of nutrients. An important thing to remember, is full fed pigs generally eat to meet their energy requirements. You are going to see the same thing with poultry. It doesn’t matter, necessarily, how much protein they need, the energy is going to be the limiting factor. Two major components that the producer is going to be interested in are you are going to have to feed the energy requirement for maintenance and the energy requirement for production. Maintenance is basically going to be a function of body weight and production is really going to be a function of composition. That is why I tried to put that composition graph up there.

This is a flow diagram of energy partitioning in the growing pig.

You guys have probably seen this probably four or five times now for each species. The idea is you start out with gross energy and the ration you feed and you are going to end up with a defined maintenance and production amount of energy and those are what you’re concerned with. A couple of points that I probably should point out concerning the NRC, they use digestible energy as their basis for formulating a ration while the industry kind of going more with metabolizable energy. So, you might run into that conflict if you are balancing swine rations. It is not that big of a deal, fortunately, metabolizable energy is about 96% of digestible energy at all growth phases. Basically, just multiply this by .96.

A few words about maintenance and production energy. Basically, the way you can determine maintenance energy is it’s a function of its surface area or another way to say it is a function of its body weight. It has been mathematically worked out by nutritionists and boiled down to this formula (Body weight raised to 3/4 power is most common). This is not something I’m going to have you memorize, I just want you to understand where the NRC comes up with some of their values. So the take home message, energy requirement is going to increase with body weight. The only variable here is body weight. The bigger the carcass, the higher this value is going to be. That is where you get energy requirement increases with body weight. This is a fixed cost. That’s going to be the cost to maintain an animal with that body weight. As the pig approaches market weight, energy required just to maintain it is going to increase. The other component we’re interested in is the component that’s actually going to, if you want to think of it as currency, that’s going to fund the growth, the muscle and the fat. We have already talked a little bit about how composition changes with the pig. So now we are going to talk about one static relationship with composition. For every pound of protein or every pound of muscle that a pig puts on, it is going to cost the producer about one megacalorie of energy. For every pound of fat that that same pig puts on, is going to cost him almost five megacalories of energy. Take home message is fat accretion is roughly five times the energy cost of lean gain. It is a commodity we don’t want anyway. People do not want to eat it. They do want to pay for it. They think that it is going to give them a heart attack. And worse for the producer, it is very expensive, energetically, to put on a pig. And, remember, feed costs the producer about 75% of his cost of making a pig. That’s kind of hitting him pretty hard in the pocketbook. We have talked about maintenance as a fixed cost.

How can you grow a pig more efficiently?

How can you get more bang for your buck, in other words, knowing what we know about carcass composition and the cost of putting on tissues? Just like Dr. French said with the dairy cow, if you increase production, at the same body weight, you are going to dilute out the cost of maintenance. Same goal, we want to make these pigs put on as much muscle as we can, at any given body weight. Basically, there is a couple of ways the industry goes about this. Number one is standard genetics. You just select for animals that are going to grow more muscle and grow it faster. That is actually pretty darn effective to the point where in high lean gain genetics, down in the growing stage, these animals are actually growing so fast they cannot eat enough energy to maximize their genetic potential. What is another way of doing it? Nutrition, which is probably most applicable to this class. Down here, you want to get as much energy in them as you can because more of it is going to end up going to protein until he actually maximizes his potential. Over here, when muscle is going down and fat is going up, you are probably going to want to limit-feed the animal. You’re going to try, and the strategy will be, to reduce the energy only to a point that will support this muscle growth. However, that is actually pretty labor-intensive. You have to keep really good records. You have to be a really good manager. It is not always very achievable. And there’s another way the dairy industry uses growth hormone to increase production. Growth hormone works in pigs the same way. It will increase muscle. You will get less fat. That is exactly what you want, from a composition stand point. Growth hormone for pigs will probably never be approved in the United States. However, there is another hormone. It is called Paline; that is Eli Lilly’s trade mark. It is, actually, synthetic catecholamines. Basically, like epinephrine, your fight or flight hormone. They can give those to pigs and you will have the same effect as growth hormone. And for some reason, Paline has been approved, while growth hormones just kind of languishes.

We know what the energy requirements are. We’ve got some idea why those energy requirements are what they ar., And we understand, from a composition standpoint, how we might be able to manipulate a ration to achieve the kind of pork we want to get.

What are our energy sources? If you remember back to the cartoon of the stomach. I said it has to be a highly digestible carbohydrate source. The major source of dietary energy for the pig is going to be starch. In this case, corn is by in far the best cereal grain to achieve these goals. In fact, about 85% of the grain fed to swine is just corn. I guess you would call it the gold standard. It is the best you can feed. It is highly digestible. It is very palatable. It is low in fiber, which is good for the G.I. tract of the pig. And there is a lot of ways you can process it and present it to the animal. Negatives, almost no crude protein. Well, there’s some crude protein but almost no lysine. You can see why that might be a problem in a minute. If you look at other cereal grains, you’ve got a few choices. Wheat is actually a good alternative to corn. It has a higher protein and lysine content. The carbohydrates are actually pretty bioavailable. The only problem is a lot of wheat ends up going to human consumption. So it is just not practical from a market standpoint to feed it to your pigs. It is going to cost you too much. Sorghum is probably the best alternative. If they are not feeding corn or they are feeding more of a blend of cereal grains, you are going to find sorghum in there. But, you still have the problem of low protein and lysine. Barley and rye, they’re problematic. They are really rarely fed. The big problem with barley, for example, is the beta glucans they are just not very bioavailable, they will gum up the G.I. tract and they are going to cause problems to the pig. Although, you can buy commercially available beta glucanases, which is basically an enzyme that you’d add to the feed that can break these down and then increase the bioavailability to the animal. But in reality, at least in the Midwest, barley is not that easy to buy to begin with, so you run into cost issues. Like everything else when you are feeding an animal, it going to depend on how feeding it to your animal affects your bottom dollar. Sometimes it may work for you and other times it just not going to be practical.

One other feedstuff of importance is fat. I think that it is pretty obvious, fat is a very energy dense feedstuff that you can actually feed. This table basically just is another way of demonstrating what I just said in text.

Relative value is relative to corn; which we said is our gold standard. Then, it also kind of illustrates the maximum amount you could really, practically, put into the ration. The reason I put this up here, it is a bit redundant, but I wanted you guys to appreciate this for when you are doing your ration homework. Kind of give you a rough idea. If you are trying to get your numbers to balance out. Is the ration you are actually trying to formulate really practical? It is the kind of thing that you might want to comment on when you hand your homework in.

One comment with fat while we are here. You really cannot put much fat into the ration. That is because it so energy dense and pigs primarily eat to meet their energy requirements. So, what happens is that you have such an energy dense ration that protein automatically becomes limiting just because they don’t eat enough of the ration.

I just wanted to quickly talk about one other aspect of how your ration formulation could actually be an important management tool. This is a graph.

It seems a lot more busy than what it actually is. We have ambient temperature out here, it is just the outside temperature, versus relative response growth parameter, for instance, feed to gain ratio, body temperature, daily gain, etc. What it is trying to illustrate is, you’ve got a comfort zone, relatively wide range of temperatures the pig can actually exist in comfortably, where you do not have any real physiological problems. However, when temperature gets really low, you have a problem. The pig has to obviously maintain its body temperature. It needs more energy to increase heat production. When temperature gets really high, the pig has a problem dissipating its heat. I do not know how many of you people are very familiar with pigs. They are not really good at dissipating heat. You do not see a pig sweat a whole lot. The point I would like to make is anytime you have your feed to gain ratio going up, it is probably because there is a bigger energy demand on the animal. What happens is your energy is going away from production, going away from making muscle, to actually, in this case, maintaining body temperature. So, you can imagine what it’s doing to your bottom-line. You are feeding the animal just so he can basically increase his maintenance and that is not a good way to stay in the business. To relate this back to the ration, just remember this relationship, requirements are greater for energy at lower temperatures. It just makes sense. When it is really cold out, the pig needs more energy, to generate more heat, to maintain its body temperature. It is not rocket science.

How can you use certain feedstuffs to monitor or to regulate the ability of this pig to deal with temperature? One way is dietary fat it releases less heat, just in the process of digesting and absorbing it; that is called heat increment. I do not know if you remember from 311. It releases less heat, just through the process of getting it into the body to metabolize. So, that means the pig can actually tolerate it a lot more. There is less heat stress associated with eating this ration. When it is really hot out and you have an opportunity to add fat to the diet, it might be a good thing to do because they can actually tolerate your feed better. Their feed intake is not going to decrease. And you are not going to see your rate of gain decrease either. Provided you can get the fat and it is relatively cheap, it probably would be a good production tool to use. Now, when the temperature is really cold fat is not going to help you as much. But, dietary fiber can actually do the trick for you. Basically, dietary fiber is going to release more heat increment, more heat as heat increment, going through the digestive and absorption process. So, the idea is feed more dietary fiber and you are going to generate more body heat.

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