What is the ideal amino acid profile in pig diets?

Giannis Karvelis, Nuevo S.A, g.karvelis@nuevo-group.com

Some time ago, I was invited to participate in the ‘Healthy Start – Healthy Finish’ symposium held in Cookstown & Cavan, Ireland with a technical presentation of a less often addressed approach feed topic. As most aspects of pig nutrition are quite often over-analyzed I focused on my experience and ideas on the main principles I follow and decisions process I take in my diet formulation routine.

This in turn, led me to focus for my presentation (available at www.nuevo-group.com ) on the most expensive nutrients of the diet which are energy and protein. After an overview of the latest developments in energy and amino acid nutrition (where the industry is today and a survey of previous years’ trials and results), a question from the audience on the necessity or otherwise of applying a different SID amino acid profile depending on the genetics gave me the idea for this article.

Before going further, I should state that there is no doubt that with the knowledge and information we have at hand as nutritionists nowadays we can move from protein based diets to essential amino acid based diets and pigs will perform equally well or even better in some cases! This has been repeatedly demonstrated in a large number of trials and scientific data gathered.

Accepting this, it is important to note that the most significant single factor affecting the efficiency of protein utilization is the profile of digestible essential amino acids entering the small intestine. In pig diets, unlike in ruminants, this supply is almost entirely influenced by the diet. Lysine is of course the first limiting amino acid and the correct practice is to express the requirements for all other essential amino acids relative to Lysine.

Lysine requirements for both nursery and finishing pigs have increased in recent years and vary with environmental conditions and genotype, when expressed relative to growth rate. By adapting either the equations of Main et al. (2008) and the NSNG (National Swine Nutrition Guide) or the latest data presented by NRC, it is safe to accept that nursery pigs will require approximately 18-19 grams of SID Lysine per Kg gain whereas finishing pigs will have slightly higher needs close to 20 grams of SID Lysine per Kg gain.

The requirements for the other essential amino acids in relation to lysine must also be adjusted during feed formulation in such a way that dietary crude protein level is kept as low as possible in order to promote gut health and ensure performance. A summary on the amino acids recommendations for piglets and finishing pigs is shown in Table 1 below.

One important consideration that has arisen as a result of the feed antibiotics ban and growth promoter elimination is the interaction between nutrition and health. Feeding pigs based on their immune status is very much related to lower feed intake (which is the end result of any immune challenge). Healthy pigs with low immune system activation have higher need for dietary lysine as their ability for protein deposition is greater compared to unhealthy pigs with high immune system activation. However diets well balanced in terms of Energy/SID Lysine, with high quality/digestible ingredients are equally valuable for both healthy and immune challenged pigs.

Table 1. Amino acids profile for piglets/pigs

BW, Kg6.5-1212-2323-4040-6565-8585-105105-125
 Standardized Ileal Digestible
Meth + Cys58-6058-6058-6058-6058-6058-6058-60
Phe + Tyro94949494949495


Special attention should also be given to Threonine as this is the most utilized amino acid by the gut. Under poor sanitary conditions or health challenges, its utilization for protein synthesis and therefore growth, might well be limited! For more details on Threonine’s role check the link: https://www.feedstrategy.com/pig-nutrition/pig-gut-health-understanding-the-role-of-threonine/

What also needs to be highlighted is that the supply of Valine, which is the sixth co-limited amino acid, is coming under more scrutiny as all data suggest that the SID Lysine:Valine ratio drives feed intake in young pigs. Following this, Isoleucine dietary supply also becomes more important as it is the following limiting amino acid after Valine and getting to its required dietary level could well be the determining factor in arriving at the overall content of protein of the diet formulated.

Special attention should also be given to Leucine as its excess, which often can arise in diets rich in animal blood products, coupled with an incorrect SID Lysine:Valine ratio may prove detrimental to piglet performance.

Now coming back to the original audience question: should we apply a different amino acid profile for different genetics?

Well, my answer during the event was no and remains the same…as I can’t really come up with any reason why the amino acid profile should be different. On the contrary, I think we are struggling enough to decide what the ideal amino acid ration is anyway that I believe, applying a different profile to different genetics is an unnecessary level of sophistication.

Nevertheless, it should not be overlooked that Pietrain pigs may have a smaller gut and as such slightly less amino acids available for intestinal growth and maintenance. Faced with this, the first action to take is to increase the dietary SID Lysine levels as this will ensure that the diet is sufficient to meet the pigs’ essential amino acid requirements.