The leading amino acid

In European feed formulas, lysine is the first limiting amino acid for pigs and the second one after sulphur amino acids (methionine + cysteine) for poultry. Being an indispensable amino acid for pigs and poultry, lysine has to be supplied by the diet.

In broiler chicken nutrition, there is a direct link between the daily lysine intake and the development of certain muscles such as breasts. Therefore, adjusting dietary lysine content enhances the value of meat cuts in case of further processing.

Since lysine is the first limiting amino acid in pig nutrition, its intake is one of the main factors which determine pig growth rate. Feed intake being often limiting for the expression of the growth potential, the only way to increase lysine intake is to raise the lysine dietary concentration and balance the feed to make sure that all the lysine provided can be valued for protein deposition (ideal protein concept). Lysine levels must be adapted to the animal feed intake and to the targeted average daily gain (Figure 1).

Digestible lysine level in feed

Figure 1. The dietary standardized ileal digestible lysine dietary concentration should be defined upon the observed feed intake and the targeted weight gain.

The amount of lysine ingested on a daily basis has a direct influence on animal growth performance as lysine is mainly used for body protein deposition (Figure 2). Adjusting the dietary lysine concentration according to the animal growth potential and feed intake capacity makes it possible to optimize not only growth but also feed efficiency.

Digestible lysine level in feed

In each experiment, the best ADG and the corresponding amounts of ingested lysine were highlighted with red circles. Then, the ingested SID lysine level needed for a given ADG is estimated by a linear model (blue line).

Figure 2. Effect of ingested lysine (standardized ileal digestible, SID mg/day) on average daily gain (ADG) of piglets in different experiments (black curves) and estimation of the SID lysine requirement per gram of gain (blue line).

L-Lysine supplementation in monogastric feeds represents thus a simple, effective and accurate way of adjusting lysine content to animal requirements in order to optimize the technico-economic results of the production. L-Lysine also allows limiting the use of protein-bound lysine which is contained in vegetable protein such as soybean meal; this in turn reduces dietary crude protein levels and, as a consequence, reduces nitrogen excretion from animal husbandry in the environment. Moreover, as L-Lysine is 100% digestible, its utilization by the animal is far greater than that of protein-bound lysine from vegetable proteins.

For these reasons, L-Lysine is the "leading amino acid" used in both pig and poultry feeds with regard to quantity and frequency of supplementation. The results of the feed surveys which we regularly carry out throughout Europe have shown that frequency of L-Lysine supplementation is greater than 95% in commercial pig and poultry feeds, irrespective of the stage of the animal’s growth. Its use is also common in feeds for rabbits and pre-ruminant calves and it is quickly developing in fish feeds, aquaculture and petfood.

For further information, please read our technical bulletins: numerous experimental results are reported.