Animal Nutrition

Essential amino acids in pig diet: the balance to be followed

When we go through the role of essential amino acids in pig diet, a number of factors need to be taken into account, such as the nutritional evaluation of feed raw materials, the requirements related to each of the essential amino acids, the management of feed and the formulation of feeds that guarantee to the animals an adequate zootechnical performance.

Amino acids are the basic units of proteins. Of the 20 major amino acids that exist in nature, 10 are considered essential for pig metabolism.

These should be acquired exclusively through diet, as their bodies are unable to synthesize them.

The essential amino acids are:

•  Lysine;
•  Threonine;
•  Methionine;
•  Tryptophan;
•  Valine;
•  Isoleucine;
•  Leucine;
•  Histidine;
•  Phenylalanine;
•  And tyrosine.

To ensure that all of these amino acids are present in swine feed, it is possible to formulate feeds by adapting the protein level to meet these requirements.

In order for this strategy to be successful, a deep understanding of the requirement for these amino acids for pigs, their functions and ways of balancing them in diets is required.

A not too smart strategy to cut costs

Because it accounts for the largest fraction of pig farming costs (75-80%), feed often ends up having low-cost ingredients, usually with reduced protein and increased fiber.

Although this is not a surprising fact, it is a very harmful strategy to animals, since low quality nutrients have lower digestibility and hinder their development.

Many diets use protein sources of plant origin mainly soybeans, which, despite having a relatively high amino acid digestibility, have a considerable content of fiber-bound proteins.

Since fibers are not digestible, the proteins attached to them also end up following the same metabolic pathway.

In addition to concerns about the availability of proteins for digestion, attention must also be paid to limiting amino acids.

What are limiting amino acids?

The limiting amino acids are those that need to be contained in the diet in limited concentration minimum, according to requirement for protein synthesis to occur.

Thus, even if all essential amino acids are part of the diet in balanced amounts, except for the limiting, synthesis is not performed.

For pigs, the main limiting amino acids are, in a feed with conventional ingredients, lysine, methionine, threonine and tryptophan.

Lysine is the main limiting amino acid in pig diet. It is extremely essential for protein synthesis because if lysine is not present, protein synthesis cannot be performed.

As a result of this factor, it is one of the most studied amino acids in animal nutrition.

At all stages of pig life, lysine should be present at 100% of the recommended level, as this is the most limiting of all amino acids.

In contrast, methionine needs to be present at 28% of the recommended of lysine diet level of newborn piglets, from 29 to 31% for growing and terminating pigs, 27% for gestating sows and 25-28% for lactating sows.

Threonine is present in many cereal grains and its bioavailability is low in piglet feed ingredients.

In addition to participating in protein synthesis of muscle tissue and milk, this amino acid is involved in other physiological functions such as ingestion and immunity.

Threonine needs to be part of the newborn piglet diet at 62% of the recommended level of lysine, 63-68% for growing and terminating pigs, 74-76% for gestating sows and 59-66% for lactating sows.

Tryptophan is a precursor to serotonin, a neurotransmitter that is linked to stimulating food intake. When deficient, it negatively affects voluntary food intake and performance of pigs in termination phase.

The newborn piglet diet should contain 17% of the recommended of lysine level, 16% for growing and terminating pigs, 18% for gestating sows and 18-20% for lactating sows.

The search for the ideal protein source

The ideal protein would be one that has a perfect balance of amino acids, balancing the essential with the nonessential ones, avoiding any excess or deficiency. This ideal protein would be reflected in pig growth and maintenance.


It can be said that the ideal protein is the one that provides 100% of the recommended level of each amino acid. As one can imagine, it is not an easy task to find such a protein source in the nature, especially when it comes to plant sources.

Because of this difficulty, the concept of precision nutrition has emerged, which means the adequacy of the protein level of feed to meet the requirements of essential amino acids precisely. In addition to reducing formulation costs using all available technology.

To this end, industrial amino acids such as L-lysine, L-threonine, L-tryptophan and L-valine are used to supplement protein sources that do not have the ideal amino acid balance. In addition, the need to incorporate other protein sources to balance it is reduced, which lowers feed costs.

In theory, this is an interesting solution from both a nutritional and an economic point of view.

However, the economy that is a consequence of reducing protein sources, ends up becoming other types of expenses. For example, most synthetic amino acids are present in dehydrated or liquid form. To use the liquid form, pumps and measuring equipment must be purchased in order to incorporate them into the feed.

Because the amounts of each amino acid are accurately calculated, measuring equipment must be highly accurate. Added to that, mixing equipment is also required to incorporate industrial amino acids into feed.

So often, this option ends up being even more expensive.

Considering these limitations, animal protein sources continue to be a more interesting dietary options for pigs.

Ingredients produced with fresh raw material such as chicken protein hydrolysate, for example, in addition to having naturally in their composition all essential and limiting amino acids in a balanced way high digestibility and that also have the extra benefit of bioactive peptides with antibacterial activities, antioxidants, immunostimulants, among others. These additional benefits are due to the biotechnological process of enzymatic hydrolysis. You can learn more about this ingredient and its application in pig nutrition in this blog post

Not to mention the high digestibility of proteins, which ensures a good use of it by the body of pigs, which will result in rapid growth and development.


The variability of amino acid nutritional requirements in pig diets depends on several factors such as age, weight, breed and other particularities.

However, regardless of the differences, it is necessary to be aware of the issue of essential and limiting amino acids, since their deficiency can significantly affect the development of animals.

The choice of the protein source, always paying attention to the quality of the proteins present and the amino acid balance, is fundamental for the success of the pig farming.

Feel free to leave a comment

Get awesome content on inbox   Subscribe

BRF© 2019. All Rights Reserved.