Ask a swine nutritionist what limits performance in a maize-soy diet and the answer is usually one word: lysine. Ask a feed mill manager what they buy most of in the amino acid line and the answer is the same. L-Lysine sulphate (CAS 60343-69-3) is the volume product of that demand – a dried fermentation concentrate rather than a purified salt.
This guide is about using it in practice: how each species’ requirement is expressed, how to convert it into an inclusion rate, how the ideal-protein approach works when you cut soybean meal, and where the sulphate form fits better than the hydrochloride.
Why lysine is the reference amino acid
In cereal-based diets, lysine is almost always the first limiting amino acid: the animal’s requirement is high relative to what maize and wheat provide, and no amount of extra protein helps if lysine runs out first. Nutritionists therefore express the whole amino acid profile as a ratio to lysine – the “ideal protein” concept.
| Amino acid | Typical ratio to lysine (grow-finish pig) | Note |
|---|---|---|
| Lysine | 100 (reference) | The basis of the whole matrix |
| Methionine + cysteine | 55-60 | Second limiting in many diets; usually supplemented as DL-methionine |
| Threonine | 60-65 | Third limiting; crystalline threonine is standard |
| Tryptophan | 17-19 | Often adequate in maize-based diets, limiting in wheat-based ones |
| Valine | 65-70 | Becomes limiting at very low protein levels |
The ratios are indicative and vary with genotype, weight range and production target – but the principle is fixed: once you set the lysine level, every other amino acid follows from it. That is why the lysine source and its accurate assay matter so much.
From requirement to inclusion rate
The calculation is straightforward but is done wrong surprisingly often, because it mixes up three different numbers: the requirement (g lysine per kg feed), the product’s lysine content, and the moisture correction.
| Step | Example |
|---|---|
| 1. Requirement | Grow-finish pig, 10.0 g available lysine per kg feed |
| 2. Lysine already supplied by ingredients | Maize + soybean meal + other ingredients give 8.2 g/kg |
| 3. Deficit | 1.8 g/kg to be supplied |
| 4. Product assay on dry basis | 56.0% lysine; moisture 3.0% delivered lysine = 56.0 x 0.97 = 54.3% |
| 5. Inclusion rate | 1.8 / 0.543 = 3.3 g product per kg feed = 0.33% |
Step 4 is where cheap errors hide. Using the nominal 55% instead of the moisture-corrected figure under-doses by about 3%; across a year of feed production that is a real performance difference – and an easy one to avoid.
Species-specific notes
Swine
The largest single market. Lysine requirement falls steeply with body weight: a 10 kg piglet needs a far higher dietary concentration than a 90 kg finisher. The sulphate form is standard in grow-finish diets because the inclusion rate is high enough (0.2-0.8%) that the granular handling advantage matters, and the cost per unit of lysine is lower than the hydrochloride.
Poultry
Broilers have a high lysine requirement relative to energy, and wheat-based diets are typically lower in lysine than maize-based ones. The sulphate form works well in mash and pelleted feed; in crumble and fine premix applications the hydrochloride’s higher concentration is sometimes preferred.
Aquatic species
Fish and shrimp have high protein requirements and correspondingly high lysine demands per unit of feed. Inclusion rates are higher than for terrestrial species, which makes the cost per unit of lysine the dominant commercial factor – a natural fit for the sulphate form. Water stability of the pellet matters too; the granular product handles extrusion and conditioning well.
Ruminants
Unprotected lysine is fermented in the rumen, so the sulphate form is not used directly for dairy or beef. Only rumen-protected lysine sources deliver lysine to the small intestine – a different product category with a very different price.
Cutting crude protein without losing performance
The economic case for lysine supplementation is not “add lysine, grow faster”. It is “add lysine, remove soybean meal, keep performance”.
| Change | Effect |
|---|---|
| Reduce crude protein by 2-3 percentage points | Less soybean meal; lower feed cost |
| Supplement lysine, methionine, threonine, tryptophan | Amino acid profile maintained at the requirement ratios |
| Result | Same growth, less nitrogen excreted, lower cost |
The limits of this approach are real: below a certain crude protein level, the next amino acid (often valine or isoleucine) becomes limiting, and performance falls unless it is supplemented too. This is why the low-protein journey is walked one step at a time, with the lysine source as the anchor.
Sulphate or hydrochloride: the practical decision
| Situation | Better fit | Reason |
|---|---|---|
| High-volume swine or poultry compound feed | Sulphate | Lower cost per kg lysine; granular handling; high inclusion rate tolerates the lower concentration |
| Premix or low-inclusion application | HCl | Higher concentration keeps premix volume manageable |
| Aquatic feed at high inclusion | Sulphate | Cost per unit lysine dominates |
| Diets with a tight sulphur budget | HCl | The sulphate form contributes sulphur |
| Humid storage conditions | Sulphate | Less hygroscopic, less caking than the fine crystalline HCl |
A worked cost comparison is in L-lysine sulphate vs L-lysine HCl.
Quality control at the feed mill
| Check | Frequency | What it catches |
|---|---|---|
| Lysine assay (dry basis) + moisture | Every lot | Delivered lysine per tonne; the basis of every formulation calculation |
| Appearance and flowability | Every lot | Drying quality, caking risk |
| Heavy metals, microbiological limits | Per supplier qualification, then periodically | Feed safety compliance |
| Pelleting trial | On supplier change | Durability and fines generation |
Frequently asked questions
How much lysine does 1 kg of product deliver? About 0.53-0.55 kg depending on moisture, because the 55% specification is on a dry matter basis.
Is the sulphate form lower quality than the hydrochloride? No – it is a different product with a different specification. It contains less lysine per kilogram and more other nutrients; both are standard feed additives.
Can it be used in organic feed? Depends on the certification scheme; confirm with your certifier and request documentation.
Does it affect pellet quality? Granular material generally handles conditioning and pelleting well; confirm with a durability test on your own line.
Contact PolyBlueChem for specifications, samples and formulation support.