Global survey of limestone used in poultry diets: calcium content, particle size and solubility

Limestone is used in poultry diets as a calcium (Ca) source. Feed formulation often based on an estimate of limestone Ca content or, less frequently, wet chemistry analysis. However, composition may vary, which has not previously been studied large scale. In this study, 641 samples supplied to feed mills 40 countries across eight global regions were collected and analysed for macro- micromineral content, particle size (geometric mean diameter, GMD), vitro solubility. Mean fine (GMD<1000 μm, n=566) was 37.8% (range 33.3-39.7%) coarse (GMD>1000 n=75) 38.0% 34.7-40.0%). There marked variation among within the concentration other macro minerals microminerals. Particle (GMD) 288 μm 37.7-991.9 μm) 1,689 mm 301.6-3,067.9 μm). solubility (5 min incubation, pH=3.0) 68.4% 18.8 99.4%). only explained 52% 5 incubation (R 2 =0.52). For limestone, (30 incubation) 65.5% 23.2-96%) correlated =0.09) with size. rate have shown alter phosphorus utilisation broilers laying hens. Hence, better understanding mineral analysis, would enable more accurate inclusion subsequently digestibility support health performance.