Limestone, the predominant Ca source in poultry feeds worldwide, can have particle sizes that are widely different, from less than 75 um to more than 800 um, which will impact the concentration of reactive (soluble) Ca. There is a well-documented detrimental impact of Ca on P digestibility, but the impact of limestone particle size which is highly correlated with its solubility and is a key determining factor on the degree of impact of Ca from limestone on P utilization, has been less studied. Limestone currently used in animal production varies considerably in particle size, purity and solubility. Neither of these three parameters by itself dictate the availability of Ca for animals or the impact of Ca on the digestibility of other nutrients (e.g.phosphorus). The variation in Ca solubility must be considered to properly assess the interaction, of Ca with phytate and phytase and to formulate diets for optimal animal performance.
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