Crude Protein Levels

When we talk about crude protein levels in feed and how that relates to the efficiency and value of that feed we get excited. That’s because if you understand this concept, you are ahead of most feed store shoppers in understanding feed quality. Particularly when feeding animals like pigs and chickens, if you read the label and evaluate feeds you are considering in terms of a couple of numbers you will save yourself a lot of time, money, and frustration. 

Forget “crude protein.” There’s a reason it is called crude. It doesn’t mean much, really.

When crude protein is quoted, it is a measure of how much nitrogen is in a certain product. Nitrogen can be very well utilized — think eggs and milk and meat and certain legumes as high-quality sources of protein. Or it can be nearly worthless. Some kinds are not even digestible. Leather has a great crude protein content, but it is worthless as a feed, as you would guess. The fertilizer you put on plants is usually high in nitrogen – and hence, protein – but if you fed it to your dog you’d be visiting the vet. In fact, when the Chinese protein meal containing melamine killed all those pets a number of years ago that’s exactly what happened. It was high in protein, but it was in a form they couldn’t use, and it killed them.

Grains have proteins in the form of amino acids, but not the kind that builds muscle or eggs in the animals that consume them. The amino acid contained in grains is calleed “methionine” though it is truly several amino acids working together. It forms skin and feathers and supports daily living. 

“Lysine” is the amino acid that builds muscle and eggs, and we find that in meats and legumes like peas and alfalfa. 

Neither will work without the other being present in the right proportions.

If one feed is 16% crude protein, while another is 18% crude protein, can you safely assume that the 18% product us better for growing young animals, producing meat or eggs?  Probably, but not always. But there is an easy way to choose.

Without getting into all the technical reasons why this is so, let’s trim it down to one word: lysine. Lysine is the amino acid (the protein part) that is the most easily used by animals like us that have one stomach.  People, pigs, chickens and other monogastrics (single-stomach animals, not like cows) need lysine to build muscles and fuel construction and repair projects in the body. Fortunately, by law that number is on the feed tag as a percentage.

If you are choosing between a feed that is low in lysine – let’s just say it is .6% — against one that is higher in lysine, like .8%, the higher lysine feed is not just a little better. It’s a whole lot better because the animal is going to use up a set amount of that lysine just to stay alive. If that’s all that is available, the animal will stay alive but won’t have any leftover lysine to lay eggs or grow or perform like we want.

Some activities take more lysine than others. Feeder pigs might need their lysine percentage to be up around 1% because they are actively growing. Adult sows at maintenance levels may be able to squeak by at .5% because they are just hanging out between litters.

There’s a world of difference between those two numbers. For every percentage point there is a very significant increase in effect that compounds exponentially. A feed with a lysine content of .9% is going to be much, much better than a similar feed of .8%, and so on. In general, lysine is expensive, so it is the ingredient most likely to be in short supply.

Now for birds, methionine is very important as well. Methionine is crucial in growing feathers, skin quality, and foot health. It’s important for hair, hooves and skin for other animals too, and it needs to be in balance with the lysine. We pay very close attention to it and to the other “limiting” amino acids also, particularly threonine and tryptophan. It’s commonly found in grains, and if it is short supply birds can have feather and skin quality problems.

If you need for your feed to perform for you and do more than just keep the animal alive, consider using the feed with the higher lysine content. If the animal is just existing, lower lysine is fine. The higher the lysine, the higher the value to a pig or chicken or other monogastric animals. For a bird, methionine is critical also. We cover all the amino acid bases for you, so you can be confident that your animals are getting what they need. A balanced feed is an investment that will pay you back in a healthier, better producing animal.