<p dir="ltr">This study was comprised of two parts. The first being the exploratory in vitro element of the trial, which is set to titrate multiple different limestones in order to obtain the ABC values of a range of limestones differing in their physical and chemical characteristics. The second is the in vivo part of the trial, which, using a range of limestones with graded ABC values, as determined in the first part of the study, would quantify the effects of feeding broilers limestones of varying ABC values on Ca and P digestibility both in the presence and absence of phytase. Data were captured and analysed using JMP 16.0 (JMP, 2022), using a full factorial analysis with block included as a random effect. Correlations were determined using Pearson correlation analysis, with significance set at P < 0.05. Correlation analysis reported the strongest correlations between GMD and ABC at 120 minutes (-0.43), and between 5-minute solubility and ABC at 120 minutes (0.48).</p><p><br></p>