What is calcium carbonate?
Calcium carbonate is a naturally abundant mineral found in limestone, marble, chalk and the shells of molluscs. Feed-grade calcium carbonate is usually produced by crushing, grinding and sieving high-purity limestone or marble into defined particle sizes; precipitated calcium carbonate is also available.
Pure calcium carbonate contains about 40% calcium. Commercial feed limestone is somewhat lower because natural rock contains small amounts of magnesium carbonate, silica and other minerals, so the actual calcium content is always taken from the analysis of the product.
What does it do in animal feed?
Calcium is needed for bone formation, eggshell production, milk production, muscle contraction, nerve function and blood clotting. Calcium carbonate is the most economical way to supply it.
- Laying hens: the largest calcium requirement of any farm animal because of eggshell formation; part of the limestone is usually given as coarse particles, which stay longer in the gizzard and release calcium during the night when the shell is formed.
- Broilers and pigs: supplies calcium for skeletal development, balanced with phosphorus.
- Dairy cattle: a calcium source in rations and mineral feeds, especially in lactation.
- Premix carrier: finely ground calcium carbonate carries and dilutes vitamins and trace minerals so that small amounts can be mixed evenly into feed.
Calcium carbonate as a premix carrier
A carrier makes up the bulk of a premix and determines how evenly micro-ingredients are distributed. Calcium carbonate is widely used because it is inexpensive, chemically stable, low in moisture, free-flowing and has a suitable density and particle size.
It is not inert nutritionally, however: the calcium it contributes must be counted in the diet formulation. In piglet diets, calcium carbonate has a high acid-binding capacity, which can raise stomach pH; nutritionists therefore consider the total limestone level in starter diets. For some premixes, other carriers such as wheat middlings, rice hulls or clay-based carriers may be preferred.
How is the calcium requirement assessed?
Calcium requirements depend on species, age, production stage and performance level, and are given in nutrient requirement tables and breed guidelines. They are always considered together with phosphorus: the calcium-to-phosphorus ratio and the level of phytase used in the diet both matter. Excess calcium can reduce the availability of phosphorus, zinc and other minerals and can lower the efficacy of phytase, while a shortfall affects bones and, in layers, shell quality. Particle size is also part of the assessment, especially for layers.
Quality criteria for feed-grade calcium carbonate
- Calcium content: confirmed by analysis for each lot.
- Magnesium and insoluble matter (acid-insoluble ash): indicators of purity.
- Heavy metals and fluorine: lead, cadmium, arsenic, mercury and fluorine within the undesirable-substance limits of feed legislation.
- Particle size distribution: fine for premixes and mash feed, coarse for layers, depending on use.
- Moisture: low moisture supports flowability and premix stability.
- Traceability: a certificate of analysis (CoA) and lot number for every batch.
CTF Premix and calcium carbonate
Calcium carbonate can be included in CTF Premix's vitamin, mineral and custom premixes according to the customer's formulation, as a carrier or as a calcium source. Premixes are produced at our 10,000 m² facility in Ankara under ISO 9001:2015 and GMP with full lot traceability, and each lot's certificate of analysis can be viewed on the batch verification page.
This page is for general information. Inclusion rates and product choice should be decided with a nutritionist, taking into account the species, the feed formulation and the applicable regulations.