Limestone is the main calcium source in most poultry and livestock rations. To a feed mill it is a commodity ingredient, but not an interchangeable one: the calcium content sets the inclusion, the particle size changes how that calcium is used, and the contaminant limits decide whether it can go into a ration at all.
Calcium content and how it is reported
Rations are formulated on elemental calcium, so that is the figure to specify, with its method. A carbonate assay converts to calcium, but the conversion carries whatever else is in the material. AragoCor’s material is 38.51% elemental calcium and 96.17% CaCO3, with 0.24% MgCO3, all representative analysis by ASTM C 25 — measured on a sample, so the figure a formulator relies on is the one confirmed for each lot.
Particle size: why it differs by species
Particle size changes how calcium is released in the digestive tract. Fine limestone dissolves quickly; coarse particles are retained longer. That is why nutritionists formulating for laying hens often include a coarse fraction alongside fine material, while other rations call for a fine, consistent powder. The distribution is the nutritionist’s decision for each species and production stage; the mill’s job is to specify it and receive it consistently.
Write the specification as a sieve distribution with the openings stated, and say whether results are cumulative passing or retained, because supplier sheets use both. AragoCor publishes AG-CAL, the grade used in feed formulations, at 0.2–0.5 mm as a published range, and offers custom classification for feed rations to customer specification.
Solubility is part of the same question. Aragonite is the more soluble calcium carbonate polymorph, by published reference solubility products, and how that interacts with particle size in a ration is something a feed trial establishes, not a data sheet.
Moisture
Feed mills meter limestone as a dry, free-flowing ingredient, and moisture affects flow, caking and the mass of calcium per ton delivered. AragoCor publishes moisture as received at 5–10%, a published range. A mill that handles limestone through dry-ingredient bins should agree the moisture basis and limit in the purchase specification.
Contaminants and documentation
Feed regulations and mill quality programs limit undesirable substances in mineral ingredients, commonly heavy metals such as lead, arsenic, cadmium and mercury, and fluorine. The limits vary by jurisdiction and species, so put the ones your program applies into the purchase specification and require results against them, by method, for each lot or at an agreed frequency.
Listings are separate from composition. AragoCor’s material carries the OMRI livestock feed-material listing avw-23215. It concerns organic feed programs; it is not a nutritional claim, an inclusion rate or approval of a finished ration, and the regulatory status of a feed ingredient should be confirmed for the market it is sold into.
A feed-mill specification checklist
- Elemental calcium, with method, minimum and lot reporting.
- Magnesium and acid-insoluble limits.
- Particle distribution, with sieve openings and the passing or retained convention.
- Moisture as received, with a limit your bins can handle.
- Contaminant limits, methods and reporting frequency.
- Documents: safety data sheet, lot certificate of analysis and any listing your program needs.
The feed-grade calcium carbonate page covers AG-CAL for feed formulations; a mill’s own specification is the document to compare it against, line by line.
← All articles