DL-Methionine CAS 59-51-8

Introduction to DL-Methionine

DL-Methionine is the racemic mixture of D- and L-methionine, a sulfur-containing essential amino acid that animals cannot synthesize de novo. In compound feed, it addresses the first limiting amino acid deficiency in corn-soybean based diets, directly improving feed conversion ratio and breast muscle yield in broilers. Both enantiomers are bioavailable in monogastric animals, as D-methionine is converted to the L-form via hepatic enzymes, delivering equivalent nutritional value to pure L-methionine at lower production cost.

The thioether group is susceptible to oxidation under prolonged exposure to temperatures above 40 °C or high humidity, which can cause surface caking and slight yellowing. Proper sealed storage below 30 °C in dry, ventilated warehouses preserves assay and flowability for full shelf life.

DL-Methionine Chemical & Physical Properties

Applications of DL-Methionine

Poultry feed: Typically included at 0.15–0.35% in corn-soy diets to meet methionine + cysteine requirements. In broiler starter feeds, supplementation at 3.0–3.5 g/kg supports breast muscle accretion; in layer diets, it maintains sustained egg mass output. It can be mixed into premixes or added via micro-dosing systems.

Swine nutrition: Supplemented at 0.05–0.20% depending on dietary protein level. In low-crude-protein diets, it becomes the second limiting amino acid after lysine, improving nitrogen retention by 8–12% and reducing overall dietary protein requirements.

Aquaculture feed: Included at 0.1–0.3% in fishmeal-reduced formulations. Methionine is typically the first limiting amino acid when fishmeal drops below 20% of diet; supplementation improves growth and survival rates in shrimp and finfish during early growth stages.

Food-grade and pharmaceutical use: FCC/USP grade material serves as a nutritional fortifier in infant formula, medical nutrition products and sports supplements. Pharmaceutical grade is also used as a starting material for S-adenosylmethionine synthesis and hepatoprotective formulations.

Storage & Safety Precautions for DL-Methionine

• Keep sealed in original packaging at 5–30 °C with relative humidity below 70%. Avoid prolonged exposure above 40 °C to prevent caking and oxidative discoloration. Stack pallets to a maximum of 8 bags high for 25 kg units. Shelf life is 3 years under proper conditions.
• Not classified as hazardous under GHS. Use N95 dust masks and safety glasses during manual bag handling to avoid mild dust irritation. Mild sulfurous odor is normal and non-toxic. Flush eyes with water for 15 minutes in case of contact.
• Protect from rain and direct sunlight during transit. FIBC bags require pallet or sling handling; do not drag on rough surfaces to prevent packaging damage and moisture ingress.

DL-Methionine FAQ

Q: How does DL-Methionine compare to MHA in feed formulations?

A: DL-Methionine (99% active) delivers methionine directly, while MHA (88% liquid) requires hepatic oxidation to become active. On a molar basis, 1 kg DL-Methionine ≈ 1.12 kg MHA (88%). DL-Methionine is preferred for dry feed mixing; MHA suits liquid dosing systems.

Q: Can DL-Methionine withstand standard pelleting temperatures?

A: Yes. Thermal degradation below 100 °C is negligible. Standard pelleting at 70–85 °C with 10–20 second conditioning causes less than 0.5% loss, so no formulation adjustment is needed for pelleted or extruded feeds.

Q: Is slightly yellowed or caked DL-Methionine still usable?

A: Surface yellowing indicates mild thioether oxidation; slight caking comes from humidity absorption. If assay remains ≥ 98.5% and loss on drying ≤ 1.0%, the lot is acceptable for feed use. Reject food/pharma grade material if assay drops below 99.0%.