ABSTRACT

1. This study investigated the effect of dietary calcium (Ca) levels on growth performance, bone development and Ca transporter gene expression levels in the small intestine of broiler chickens.

2. On the day of hatch, 350, Ross 308 male broilers were randomly allotted to one of five treatments with five replicate pens each and 14 birds per pen. Dietary Ca levels in feed were 5.0, 7.0, 9.0, 11.0 and 13.0 g/kg, in which 9.0 g/kg was in the control diet. All diets contained 4.5 g/kg non-phytate phosphorus (NPP).

3. The increase in dietary Ca levels from 5.0 to 13.0 g/kg did not affect the growth performance of 1- to 18-day-old broilers (P > 0.05).

4. Increasing the Ca levels linearly increased the ash weight and the contents of ash, Ca and phosphorus (P) in the tibia of broilers at 18 days of age (P < 0.05). The contents of ash, Ca and P in broilers fed with 9.0 g/kg Ca were higher than those in birds fed with 5.0 g/kg Ca (P < 0.05).

5. Increasing the Ca levels linearly decreased mRNA expression levels of the Ca-binding protein 28-kDa (CaBP-D28k), plasma membrane Ca-transporting ATPase 1b (PMCAlb), sodium (Na)/Ca exchanger 1 (NCX1), nuclear vitamin D receptor (nVDR) and membrane vitamin D receptor (mVDR) in the duodenum of broilers at 18 d of age (P < 0.05). Similar results were seen in the jejunum and ileum. Broilers fed 9.0–13.0 g/kg Ca in feed had lower mRNA expression levels of CaBP-D28k and PMCAlb in the small intestine than birds fed 5.0 g/kg Ca in feed (P < 0.05).

6. The data indicated that low levels of dietary Ca stimulated its transporter gene transcription and promoted absorption, but high levels of Ca inhibited transporter gene expression and prevented excessive absorption in the small intestine of broiler chickens.

摘要

1. 本研究调查了日粮钙 (Ca) 水平对肉鸡小肠生长性能、骨骼发育和钙转运蛋白基因表达水平的影响。

2. 在孵化当天，350 只罗斯 308 雄性肉鸡被随机分配到五个处理中的一个，每个处理五个重复栏，每个栏有 14 只鸡。饲料中日粮钙含量分别为 5.0、7.0、9.0、11.0 和 13.0 g/kg，其中对照日粮中为 9.0 g/kg。所有日粮均含有 4.5 g/kg 非植酸磷 (NPP)。

3. 日粮钙水平从5.0 增加到13.0 g/kg 不影响1-18 日龄肉鸡的生长性能（P > 0.05）。

4. Ca水平的增加使18日龄肉鸡胫骨灰分重量和灰分、钙、磷含量呈线性增加（P < 0.05）。饲喂9.0 g/kg Ca 的肉鸡灰分、Ca 和P 含量高于饲喂5.0 g/kg Ca 的鸡（P < 0.05）。

5. 增加 Ca 水平线性降低 Ca 结合蛋白 28-kDa (CaBP-D28k)、质膜 Ca 转运 ATP 酶 1b (PMCAlb)、钠 (Na)/Ca 交换器 1 (NCX1)、核的 mRNA 表达水平18日龄肉鸡十二指肠维生素D受体（nVDR）和膜维生素D受体（mVDR）（P < 0.05）。在空肠和回肠中观察到类似的结果。饲喂 9.0-13.0 g/kg Ca 的肉鸡小肠中 CaBP-D28k 和 PMCAlb 的 mRNA 表达水平低于饲喂 5.0 g/kg Ca 的鸡（P < 0.05）。

6. 数据表明，低水平的日粮钙刺激其转运基因转录并促进吸收，但高水平的钙抑制转运基因表达，防止肉鸡小肠过度吸收。