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Protein

Moving on to protein. Protein is actually the first nutrient we are going to talk about. Different from ruminants in this sense, you have no specific need for protein per say, but pigs have very specific and defined requirements for certain amino acids. So, you are not feeding protein anymore, you are feeding amino acids. And that is an important distinction. There’s ten essential amino acids that have to be provided in the swine diet. All the other amino acids can basically just be made by the pig provided there is enough nitrogen in the diet. Nitrogen is never really a problem in swine diets.

Basically, the way swine nutritionists look at the amino acid problem. They use the ideal protein concept. I am pretty sure you guys are all familiar with this, so I am kind of just going to just gloss over it. That is how the NRC expresses the dietary requirements in the back of the book. It will be relative to what they call their ideal protein. What the ideal protein is it is a balance between the amino acids you are feeding in the diet relative to what has been experimentally determined the pig needs in order to have optimal growth. A quick and dirty way of thinking about it is the ideal protein is one where the amino acids in the ration really just kind of mirror the composition of the pig.

Amino acids are required for maintenance of the protein in the body. There is protein turnover; the idea is some proteins go through the cycle of degrading and then being remade. So you need a certain amount of amino acids just so that cycle can keep going. And also amino acids required for protein accretion in a carcass. This means for growing muscle in the pig. This is where your money comes from.

I said there were ten essential amino acids that have to be in the diet. The most important one and the one you are going to see on an exam is lysine. It is generally the first limiting amino acid. There are a couple of reasons why this is so. First, lysine tends to be in a high concentration in muscle relative to the other amino acids. Almost 7% of the amino acids in muscle tissue are represented by lysine. And also, remember we are feeding these pigs a concentrated diet, basically corn, soybean. It just so happens, most of the cereal grains have a very low level of lysine. So we have, from an ideal protein standpoint, we have a foodstuff with very low lysine and we are trying to feed a pig with a relatively high concentration of lysine. Since lysine is the most important limiting amino acid, it is the first one that is going to become limited, the ratio of all the other amino acids are expressed relative to lysine when you formulate a ration. That is a good thing because it makes sure, it guarantees, you are going to have enough lysine in that ration. However, it also pretty much guarantees you going to overfeed most of the other amino acids. Well, why is that a problem? Excess amino acids in the diet, they can be used for energy. But, energy is not a limiting factor in swine rations. So chances are amino acids are not really going to be used for energy. It is going to end up being degraded and secreted in the urine as nitrogen. Big problem! Both from a cost standpoint and an environmental standpoint. Number one, feed is the most expensive thing you have to deal with for making pork. Basically, you’re just throwing money down the drain when the nitrogen comes out as waste. Number two, you have 12 million hogs. All of this nitrogen has to go somewhere and you don’t want it to end up in the drinking water. What do you do to deal with it? A couple of things you can do with your ration. Probably the one that is being adopted to the greatest extent by the swine industry, they are feeding synthetic amino acids. And really it is only cost effective to do the two most limiting and that would be the lysine and methionine. What you do is you’ll balance your ration with synthetic lysine on top of the soybean meal. So actually the synthetic lysine allows you to put less soybean meal in and that takes care of over-feeding all the other amino acids.

This is basically just some data that I stole from one of the figures in the swine chapter in your textbook.

I have already said cereal grains are pretty much all low in protein. If you’re just going to feed cereal grain. First, we have some of the essential amino acids that have the greatest potential for becoming limiting. We have the requirement for the amino acid that is going to be found in the NRC and that was determined by scientists basically doing growth studies. Then, we have a percentage of each one of theses amino acids that corn alone is going to provide and corn and soybean meal will provide. The idea is corn is your cereal grain. It is low in crude protein. Basically, you can see several of these amino acids are going to be deficient. When you throw corn and soybean meal together in a balanced ration what happens is all of these requirements are met. If you compare these two columns. Actually, you see you end up with a little more than what you should have. Just reiterating what I said in the previous slide. The idea is corn and soybean meal together basically satisfies all your requirements. This is what about 90% of the industry feeds their pigs. The only time they really deviate from this is where there is a regional advantage for feeding another foodstuff. If something is cheaper in your area to get, if saves you a little money to feed it. But, if you are going to substitute another protein source for soybean meal, these other amino acids then can become limiting. It is a consideration you have to really pay attention to.

Traditionally, swine diets have been formulated based upon crude protein. Crude protein levels have been established for various weights of pigs. Basically, they do bunches of growth trials, play with your diets and then see how well you pigs grow on them. Basically, it works really good for corn and soybean. That’s been the gold standard. That is what they have done all of their work on. However, if you start switching feedstuffs because it is cheaper to feed one protein source versus soybean meal, you have to kind of ignore crude protein and you want to formulate on a lysine basis. These are some probably intuitive facts. If you thought about it, it would make sense. You wouldn’t need your notes to figure it out. When you express crude protein on a daily basis, amino acid requirements increase with body weight. It just makes sense. You are feeding amino acids to satisfy maintenance and growth requirements. The bigger a pig is going to get, he's going to have higher maintenance requirements. However, when you express crude protein as a percent of diet, the requirements actually decrease with increasing pig weight. And the idea being is the larger a pig gets the more he eats. So, that’s why that occurs. I just put this up here in case you might have to deal with that on a question on a homework. I am not even sure you will. It is there if you do.

This is the ideal amino acid pattern taken from the amino acid composition of pigs at different stages of growth.

Remember, an ideal protein is supposed to be one that closely matches the composition of a growing pig or the composition of the muscle in a growing pig. We already know that the composition of the pig is going to change with age, so it makes sense the ideal protein, the ideal amino acid pattern, is going to change with age as well. That is basically all this is showing. These are some of your major limiting amino acids. You can kind of see the biggest example would be methionine and cystine, basically changes as the pig gets bigger. So the point is we phase-feed our animals according to the stage of growth they are in. We are trying to match what we feed them precisely to what they require at each stage of growth. The whole point is we do not want to overfeed. It costs us money. It causes pollution problems. We do not want to underfeed because it is not going to maximize our growth. We are really trying to be as precise as we can and that is essentially where swine nutritionists are moving. We are just trying to better define what these requirements are. If you could just make a 2%, make your requirements 2% more accurate, you can save a lot of money when you are dealing with the size of operations that the swine industry is heading towards. It is actually a very big deal.

One thing that sometimes can be forgotten when you are formulating rations. Basically the pig, you can’t say this enough, a pig is going to eat to satisfy his energy requirement. Once his energy requirement is met, he is not going to eat. What happens is you have to really be concerned with the energy to protein ratio. Basically, calories and in protein we worry about lysine in the pig. Calorie to lysine ratio. The idea is when the energy density in your ration goes up, so you add a bunch of fat in there and it is more energy dense, the pig eats less. So what happens is when feed consumption decreases his consumption of all the essential amino acids decreases. If he does not get his essential amino acids, the pig is just not going to grow. So, your bottom dollar is really dramatically affected. The take home message is, very important to maintain energy to protein ratio in your ration to make sure that you do not have an amino acid deficiency.

So what are some of the more popular or more practical protein sources that you can feed a pig? By now you pretty much could have guessed, soybean meal is the gold standard. Even when we were doing our algebra to determine what’s the best buy, we used soybean meal as the variable we compared everything to. About 85% of the protein fed in the swine diet is going to be soybean meal. Other plant sources can be used, can be substituted. It complicates things when you are balancing a ration. Mostly because the lysine content varies so dramatically. And also some of feedstuffs are not very palatable to a pig. Pigs are kind of, you would not think it, they are omnivores, they can eat just about anything. You could feed them trash from the dump and they would eat it. But, they are also kind of picky eaters. It is kind of strange to see them select their diets. You pretty much rule out other plant sources unless the cost is just so tempting you can make money switching. The big ones are animal sources, like blood meal, things like that. They are great because blood meal is from an animal and you’re trying to match the protein composition in the diet to what is in the animal. Makes perfect sense that that is going to be a good fit. That is what I am trying to say here. AA stands for amino acid. And they have an excellent amino acid profile compared to an ideal protein. Blood meal is a great example of other considerations you need to worry about. Swine diets tend to be highly processed diets to begin with. What you see in a feed trough really doesn’t resemble what the individual feedstuff would normally look like. In the case of blood meal, what happens is, it has to be dried down. You guys know this, you are feeding a solid, you’re not feeding a liquid. The drying process is very important to the nutrient content of the blood meal. Basically, heat can degrade protein. So heat, anytime you apply it for prolonged periods or at excessive temperatures, it is going to kill your essential amino acids. The point I was trying to make, drying process is very important. Traditionally, with blood meal it was heated in such a way that you lost a lot of your bioavailability in your lysine. They have improved things with a process called ring or flash drying. What happens is you are able to get the blood meal the way you want to feed it and you have a much higher lysine bioavailability. I am not really sure why they changed. I am guessing it was solely because of that. They wanted to sell their blood meal to swine producers. It paid them to develop a new way to do it. And then a sprayed dried porcine plasma. That is basically pig blood. They take it and they separate out the red blood cells from the other blood proteins, dry it down. This is a really great alternative as a protein source because the blood proteins, for some reason, can stimulate growth and they also can ramp up your immunity. So, what you will see is spray dried pig blood given to early-weaned pigs.

Finally, my last slide basically reiterates what we have been talking about, put it in table form. I stole this from the book as well.

Everything is relative to soybean meal and then it gives you maximum percents of the diet that are practical. So, this might be a good guide, during your homework while you are balancing rations.

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