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563-71-3
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563-71-3
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Chinese name | Ferrous carbonate |
English name | Ferrous carbonate / Iron(II) carbonate |
Molecular formula | FeCO₃ |
molecular weight | 115.85 |
CAS number | 563-71-3 |
Appearance | White triangular crystals (when pure); grayish-brown powder (partially oxidized upon contact with air). |
density | 3.8 g/cm³ |
Solubility | It is almost insoluble in water (only 0.000062 g/100g at 20°C), but soluble in dilute acids. |
Iron content | Approximately 48.2% (based on Fe, theoretical upper limit) |
stability | It is easily oxidized in air—white → grayish-brown → eventually becoming the yellowish-brown color of Fe³⁺ compounds. |
Natural mineral processing
1. Selected siderite ore is crushed, ground, and graded to obtain feed-grade ferrous carbonate powder;
Chemical synthesis
2. React a soluble ferrous salt (such as ferrous sulfate) with sodium carbonate or sodium bicarbonate to precipitate FeCO₃, then filter, wash, and dry.
Chemical synthesis is a purer and more controllable route, and is the mainstream production method for feed-grade FeCO₃.
The iron in FeCO₃ is in the +2 valence (ferrous), which is oxidized to +3 valence (ferric) by oxygen in the air. The color gradually changes from white to grayish-brown, and finally to rust yellow. Therefore, feed-grade ferrous carbonate must be sealed in packaging and stored away from light and moisture. Once the packaging is damaged and exposed to humid air, the iron valence will decrease and the color will deteriorate.
Iron is an essential trace element for all animals, including humans. Its core function in the body is:
Composition of hemoglobin and myoglobin
● —Responsible for the transport and storage of oxygen. Without iron, there is no red blood.
Cytochrome and electron transport chain
● —It plays an irreplaceable role in cellular energy metabolism;
Cofactors of various enzymes
● — It participates in various physiological processes such as immunity, anti-oxidation, and DNA synthesis.
Although plant-based feed ingredients (corn, soybean meal, wheat bran, etc.) contain a certain amount of iron, their bioavailability is limited by multiple factors:
● Phytic acid (found in all grains and oilseeds) chelates iron ions to form insoluble complexes that cannot be digested by monogastric animals;
● Polyphenols and tannins in fibers can also inhibit iron absorption;
● High calcium or high phosphorus in feed will compete with iron for absorption pathways.
Therefore, inorganic or organic iron sources must be added to industrial compound feed to meet the physiological needs of animals.
Among all iron-based feed additives, ferrous carbonate has a unique niche.
Comparison with ferrous sulfate – Key differences
Comparison Dimensions | Ferrous sulfate (FeSO₄) | Ferrous carbonate (FeCO₃) |
Iron content | ~30% (heptahydrate) ~37% (monohydrate) | 4248% (depending on purity and degree of oxidation) |
Water-soluble | Very soluble | Almost insoluble |
Bioavailability | High (Gold Standard) | Moderate (effective in adult animals) |
Oxidizing/Corrosive | Strong – Easily oxidized, corrodes equipment, and destroys vitamins | Weak – More friendly to other ingredients in feed |
Hygroscopic | Strong (heptahydrate is prone to deliquescence and clumping) | weak |
Destruction of vitamins | Significantly catalyzes the oxidation of vitamins A, E, and C. | Significantly lower than ferrous sulfate |
Palatability effect | A metallic, astringent taste may affect feeding. | It has a smaller impact on feed intake. |
EFSA Evaluation | High-efficiency standard iron source | Effective in adult animals, but with lower bioavailability than ferrous sulfate in young animals. |
The core advantages of ferrous carbonate in various scenarios
Based on the above comparison, ferrous carbonate has irreplaceable advantages in the following scenarios:
1. Premixed feed with high vitamin content
Vitamins A, E, and C are all extremely sensitive to oxidation catalyzed by metal ions. Ferrous sulfate dissolves rapidly in water, releasing a large amount of free Fe²⁺—these free iron ions are "killers" of vitamins during premix storage. In contrast, ferrous carbonate is almost insoluble in water and remains in an inert solid form in a neutral pH premix system, causing far less oxidative damage to vitamins than ferrous sulfate.
For premixes requiring long shelf life and high vitamin content—such as multivitamin premixes for poultry and core ingredients in pet food—ferrous carbonate is a safer choice.
2. Animals sensitive to palatability
Pigs and chickens are far more sensitive to the smell and taste of their feed than humans imagine. Ferrous sulfate dissolves in saliva, producing a distinct metallic taste, which can significantly reduce feed intake in young animals with a sensitive sense of smell, such as weaned piglets. Ferrous carbonate, on the other hand, is inert and insoluble, so it hardly affects the taste of the feed—a point particularly important in high-end pet food and livestock feed.
3. When coexisting with other sensitive ingredients
Functional amino acids such as choline, methionine, and lysine, as well as some enzyme preparations, are prone to decomposition or inactivation in an environment with free metal ions. Using ferrous carbonate instead of ferrous sulfate can reduce the loss rate of these sensitive components.
Animal type | Add scene | Reference dosage (calculated as Fe, mg/kg feed) | Reasons for choosing ferrous carbonate |
Weaned piglets | Prevention of iron deficiency anemia | 100~200 | Use in core premixes with added high doses of vitamins to reduce vitamin oxidative loss. |
Growing-finishing pigs | Daily iron nutrition maintenance | 50~120 | Moderate cost, does not affect feed intake |
breeding sows | Iron supplementation during pregnancy and lactation | 80~150 | Protect fat-soluble vitamins in premixes and maintain reproductive performance. |
Broiler chickens | Iron supplementation during rapid growth period | 40~80 | Safe iron source when adding high doses of vitamins A/E to feed |
laying hens | Iron maintenance during egg production | 50~80 | Protects yolk quality (reduces metal-catalyzed oxidation) and does not affect eggshell quality. |
Pet dogs and cats | Iron source in complete feed | 80~200 | One of the preferred scenarios—no metallic taste and no damage to high-dose added vitamins. |
Aquatic products (fish and shrimp) | Iron source in compound feed | 100~300 | It has good stability in water (does not dissolve or leak) and has no effect on the solubility rate of feed in water. |
Aquatic feed presents a unique challenge not found in other livestock and poultry feeds—the feed pellets must remain stable in water, without disintegrating or dissolving. Ferrous sulfate is highly water-soluble, and when feed pellets containing ferrous sulfate are soaked in water, the iron dissolves and is lost rapidly. Ferrous carbonate, on the other hand, is completely insoluble in water, resulting in almost zero iron loss when the feed is in water—this is particularly critical for shrimp feed (which needs to remain stable in water for several hours).
Ferrous carbonate is one of the most unique feed iron sources – it doesn't compete for "first place in bioavailability" (that's the track for ferrous sulfate), but rather for stability, safety, and mildness.
Comparison Dimensions | One-sentence conclusion |
vs ferrous sulfate | My efficiency isn't as good as yours, but I don't destroy vitamins or affect palatability. |
vs Organic iron (ferric glycinate, ferric fumarate) | It's not as expensive as yours, but it's made from natural minerals and offers great value for money. |
Best scenario | High-vitamin premix, pet food, livestock and poultry feed, aquatic feed |
It is not a panacea for iron—for piglets that need rapid correction of severe iron deficiency (during the first week after birth), veterinarians will choose to inject dextran iron rather than administer any iron salts orally. However, in routine feed formulation, ferrous carbonate provides a near-natural iron supplementation solution that does not destroy other valuable nutrients in the feed.
It is the quiet, unassuming member of the iron family, silently doing the groundwork—just as it has existed in the Earth's crust for hundreds of millions of years in the form of siderite.
