Work was done to modify a limestone solubility assay to improve predictions of in vivo apparent ileal digestibility of Ca (AID Ca) in broilers and impacts on AID P. Limestones (LIME) were obtained from 3 commercial sources. LIME-1 (0.633 mm mean diameter, GMD); LIME-2 (ground sub-sample of LIME-1, GMD = 0.063 mm); LIME-3 (GMD = 0.326 mm), and LIME-4 (GMD = 0.831 mm). Solubility was determined at 5, 15, and 30 min of incubation using either a 0.2 N HCl (S1) or a pH 3 HCl (pH = 0.26) solution buffered with 3 M glycine (S2) to mimic gizzard and proventriculus pH. An AID trial was conducted with 320 Ross 708 male broilers. Treatments (Trt) were no added LIME, or added LIME-1, 2, 3, and 4 to achieve 0.67% Ca, to a basal diet (no added inorganic P, 0.07% Ca) with or without 1,000 U phytase/kg (36 h, 23 to 24 D of age, n = 8, 4 birds/n). Distal ileal digesta was collected from all birds and pooled by pen. Irrespective of interaction, LIME solubilized quicker and more completely with S1 vs. S2 at all time points (P < 0.05). LIME-2 solubilized the quickest, while LIME-3 had the lowest solubility through all incubation times (P < 0.05). The AID Ca was 66.30, 47.46, 19.93, and 66.33% for LIME-1, 2, 3, and 4, respectively (0 U/kg, P < 0.05). Phytase inclusion increased AID Ca by 15% on average (P < 0.05). The AID P dig was highest in no LIME added diet (74.91%) and adding LIME reduced (P < 0.05) AID P to 23.14, 12.78, 65.47, and 37.40%, for LIME-1, 2, 3, and 4, respectively in the absence of phytase. Regression showed that GMD, 15- and 30-min solubility were critical for AID Ca (R2 between 0.978 and 0.988). In conclusion, the solubility dynamics including speed and extend of solubilization, rather than a single timepoint, yield better predictions for in vivo Ca digestibility of LIME.

中文翻译：

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石灰石溶解度方法的修改以及与体内石灰石钙消化率相关的潜力。

我们对石灰石溶解度测定进行了修改，以改进对肉鸡体内 Ca 的体内表观回肠消化率 (AID Ca) 以及对 AID P 的影响的预测。石灰石 (LIME) 从 3 个商业来源获得。LIME-1（平均直径 0.633 毫米，GMD）；LIME-2（LIME-1 的研磨子样品，GMD = 0.063 mm）；LIME-3（GMD = 0.326 毫米）和 LIME-4（GMD = 0.831 毫米）。使用 0.2 N HCl (S1) 或用 3 M 甘氨酸 (S2) 缓冲的 pH 3 HCl (pH = 0.26) 溶液来模拟砂囊和腺胃 pH 值，在孵育 5、15 和 30 分钟时测定溶解度。对 320 只 Ross 708 雄性肉鸡进行了 AID 试验。处理 (Trt) 为基础日粮（不添加无机磷，0.07% Ca）不添加 LIME，或添加 LIME-1、2、3 和 4 以达到 0.67% Ca，有或没有 1,000 U 植酸酶/kg（ 36 小时，23 至 24 天龄，n = 8，4 只鸡/n)。从所有禽类收集远端回肠食糜并通过围栏汇集。无论相互作用如何，在所有时间点，与 S2 相比，LIME 在 S1 中溶解得更快、更完全（P < 0.05）。LIME-2 溶解速度最快，而 LIME-3 在所有孵育时间内溶解度最低 (P < 0.05)。LIME-1、2、3和4的AID Ca分别为66.30、47.46、19.93和66.33%（0 U/kg，P < 0.05）。添加植酸酶后，AID Ca 平均增加 15%（P < 0.05）。对于 LIME-1、2、3 和 4，不添加 LIME 的饮食中 AID P 最高（74.91%），添加 LIME 后（P < 0.05）AID P 分别为 23.14、12.78、65.47 和 37.40%在没有植酸酶的情况下。回归显示 GMD、15 分钟和 30 分钟溶解度对于 AID Ca 至关重要（R2 在 0.978 和 0.988 之间）。总之，溶解度动力学（包括溶解速度和溶解程度）而不是单个时间点，可以更好地预测 LIME 的体内 Ca 消化率。