calcium, solubility, phosphorus, broiler


Calcium (Ca) is essential for bone development mineralisation, as well as for eggshell formation, muscle and neural functions. Depending on the type of diets (veggie vs. non-veggie), species (turkey, chicken, duck), and age of animal (young vs. adult), limestone can contribute up to 95% total Ca in the final diet, with more Ca from limestone for younger animals with veggie diet. Despite the significant contribution of limestone to total diet Ca levels, the bioavailability variation of limestone Ca is rarely considered. Phosphorus (P) is a limited resource and is the third most costly ingredient in poultry diets. Improving P utilization in poultry diets will decrease the amount of inorganic P needed, reduce P excretion and feed costs, as well as increase the sustainability of poultry production. Studies in the past two decades have clearly demonstrated that Ca can be detrimental to P utilization. Some recent studies suggested that phytase, if used correctly can partially or even completely alleviate such detrimental effect. In addition, recent evidences also showed that formulating on bioavailability of Ca, instead of total Ca, could be more favourable in regard to feed cost, animal performance, and sustainability. The global limestone survey started in 2018, primarily to understand the variation of: 1) Ca concentration from the most significant Ca source and probably the cheapest ingredient limestone; 2) solubility and potentially bioavailability of the Ca from limestone. In parallel, a series animal studies were carried out to determine: 1) correlation of in vitro limestone solubility and in vitro Ca digestibility; 2) the impact of solubility profile on P digestion and phytase efficacy. It has been four years since the survey started, with over 1500 samples collected globally. It is a good time to review the results from and learnings so far.