Feed mills often compare methionine offers on price per tonne. That comparison is misleading, because the products do not supply the same amount of effective methionine per kg. A cheaper product can cost more per unit of methionine that the bird actually uses.
The right measure: cost per kg of effective methionine
Compare every source against a common reference. The usual reference is DL-Methionine 99%, with a value factor of 1.00. The value factor of any other product is the kg of DL-Methionine 99% that 1 kg of that product replaces.
Cost per kg of effective methionine = price per kg ÷ value factor
A worked example
With illustrative prices (not market prices):
| Product | Price (USD/kg) | Value factor | Cost per kg of effective methionine (USD) |
|---|---|---|---|
| DL-Methionine 99% | 2.36 | 1.00 | 2.360 |
| MHA-FA 88% (liquid), about 75% equimolar | 1.76 | 0.65 | 2.708 |
| MHA-FA 88% (liquid), about 80% equimolar | 1.76 | 0.70 | 2.514 |
| MHA-FA 88% (liquid), 100% equimolar | 1.76 | 0.88 | 2.000 |
| L-Methionine 90% | 3.79 | 0.909 | 4.169 |
Two things stand out:
- Purity matters. L-Methionine 90% supplies less methionine per kg than a 99% product, so its value factor is lower (0.909 is a purity adjustment only).
- The assumption for MHA matters most. At the same price, the MHA-FA result ranges from 2.000 to 2.708 depending on the value factor used. The hydroxy analogue is a precursor of methionine, and its relative efficacy is debated: the European Food Safety Authority concluded that the hydroxy analogues show a somewhat lower bioefficacy than DL-Methionine, while MHA manufacturers state that they are equivalent on an equimolar basis.
Value factors for MHA-FA 88%
The value factor is on a product basis: the kg of DL-Methionine 99% replaced by 1 kg of MHA-FA 88% as sold. Each factor assumes an equimolar efficacy:
- 0.65 — about 75% equimolar efficacy;
- 0.70 — about 80% equimolar, in line with the meta-analysis cited by the European Food Safety Authority in 2018 (79–81%);
- 0.88 — 100% equimolar, the MHA manufacturers' position.
Value factor ≈ active content (0.88) × equimolar efficacy × (149.2 ÷ 150.2), where the last term converts from the hydroxy analogue to methionine by molar mass. These factors are indicative until reviewed by our nutrition panel.
From cost per kg to cost per tonne of feed
To see the effect on your feed, work out the equivalent inclusion of each product:
- Equivalent inclusion = reference inclusion × (reference factor ÷ product factor)
- Cost per tonne of feed = equivalent inclusion × price per kg
Multiply the difference per tonne by your monthly feed production to see the monthly and annual effect.
Good practice
- Compare products on the same basis — the same price basis (for example CFR or landed) and the same formulation basis (total or digestible).
- State the value factor you use for each product, and its source.
- Check the specification and the certificate of analysis: the value factor assumes the product meets its stated purity.
- Confirm the result with the manufacturer's technical documentation and your nutritionist.
This is an indicative economic comparison. Nutritional equivalence depends on the product, the diet and the formulation basis. For a comparison with your own prices and formulation, ask our nutrition team.
Sources
- EFSA FEEDAP Panel (2012). Scientific Opinion on DL-methionine, DL-methionine sodium salt, the hydroxy analogue of methionine and the calcium salt of methionine hydroxy analogue in all animal species. EFSA Journal 10(3):2623 (opens in new tab) (2012)
- EFSA FEEDAP Panel (2018). Safety and efficacy of hydroxy analogue of methionine and its calcium salt … for all animal species. EFSA Journal 16(3):5198 (opens in new tab) (2018)