ABSTRACT

1. The apparent ileal calcium (Ca) digestibility coefficients of two limestone sources in growing broilers and layers were determined in two separate experiments.

2. In each experiment, two maize-based diets were developed with two limestone sources (A, experiment 1 and B, experiment 2) to contain either 8.0 g/kg Ca for broilers or 40 g/kg Ca for layers. The two sources differed in particle size, with limestone A being finer and limestone B being coarser. Each experimental diet was randomly allotted to six replicate cages and offered for 3 days from 19 to 21-day post-hatch to broilers and during 40 weeks of age to layers. The total tract Ca retention was also measured using the indicator ratios in the diet and excreta.

3. In both experiments, the apparent ileal Ca digestibility, gizzard pH and gizzard Ca concentration were higher (P < 0.05) in layers than in broilers. The apparent ileal digestibility coefficient of limestone A for broilers and layers was 0.50 and 0.62, respectively. The corresponding values for limestone B were 0.43 and 0.70, respectively. The apparent total tract retention of Ca was similar (P > 0.05) between broilers and layers in both experiments, and between the two sources.

4. The data show that the layers are more efficient in absorbing Ca from limestone than broilers.

摘要

1. 两种石灰石来源在生长肉鸡和蛋鸡中的表观回肠钙 (Ca) 消化率系数是在两个单独的实验中确定的。

2. 在每个实验中，使用两种石灰石来源（A，实验 1 和 B，实验 2）开发了两种以玉米为基础的日粮，以使肉鸡的 Ca 含量为 8.0 g/kg，蛋鸡的 Ca 含量为 40 g/kg。两种来源的粒度不同，石灰石 A 较细，石灰石 B 较粗。每个实验日粮随机分配到六个重复的笼子中，并在孵化后 19 至 21 天为肉鸡提供 3 天，在 40 周龄期间为蛋鸡提供 3 天。还使用饮食和排泄物中的指标比率来测量总道 Ca 保留。

3. 在两个实验中，蛋鸡的回肠表观钙消化率、肌胃pH和肌胃钙浓度均高于肉鸡（P < 0.05）。肉鸡和蛋鸡的石灰石 A 的表观回肠消化系数分别为 0.50 和 0.62。石灰石 B 的相应值分别为 0.43 和 0.70。在两个实验中，在肉鸡和蛋鸡之间以及两种来源之间，Ca 的表观总肠道滞留相似（P > 0.05）。

4. 数据表明，与肉鸡相比，蛋鸡从石灰石中吸收钙的效率更高。