饲粮高铁对肉仔鸡十二指肠黏膜铁转运载体基因表达及组织微量元素含量的影响

本试验旨在研究饲粮铁含量对肉仔鸡组织重要微量元素铁、锰、铜、锌含量及十二指肠黏膜主要铁转运载体基因表达的影响,探讨铁对肉仔鸡微量元素吸收和代谢的影响及其机制。将336只1日龄商品代罗斯308肉公雏按照体重随机分成4个组,每组6个重复,每个重复14只鸡。对照组饲喂不额外添加铁的基础饲粮(实测铁含量为78 mg/kg),铁添加组分别饲喂以七水硫酸亚铁(FeSO_4·7H_2O)形式添加100、250或500 mg/kg铁的试验饲粮(实测铁含量分别为166、308和579 mg/kg)。试验期21 d。各组试鸡分别于7、14和21日龄屠宰分析肝脏、心脏、胰腺、十二指肠黏膜和胫骨灰中铁、锰、铜、锌含量及十二指肠黏膜中二价金属转运蛋白(DMT1)和膜铁转运蛋白(FPN1)mRNA表达水平。结果表明:1)500 mg/kg铁添加组1~7日龄和8~14日龄的平均日增重显著低于其他3组(P0.10),250和500 mg/kg铁添加组1~7日龄的平均日采食量显著低于其他2组(P0.10)。2)饲粮铁含量对肉仔鸡7、14、21日龄的血浆总铁结合力以及全血血红蛋白浓度(7日龄除外)和红细胞压积均无显著影响(P0.10),但显著影响7、14和21日龄血浆铁含量和铁饱和度(P0.10),二者均随饲粮铁含量增加而升高。3)7和14日龄心脏及7、14和21日龄肝脏、十二指肠黏膜、胰腺和胫骨灰铁含量均随饲粮铁含量的增加而升高,7、14和21日龄十二指肠黏膜、胰腺和胫骨灰锰含量均随饲粮铁含量的增加而降低;饲粮添加铁显著降低7日龄胰腺锌含量(P0.10),但对其他日龄胰腺和各日龄其他所测组织锌含量以及各日龄所测各组织铜含量均无显著影响(P0.10)。4)饲粮铁含量显著影响7、14和21日龄十二指肠黏膜DMT1和FPN1 mRNA表达水平(P0.10),各日龄DMT1和FPN1mRNA表达水平均随饲粮铁含量的增加而降低。以上结果提示,高铁饲粮可能通过调控十二指肠黏膜DMT1和FPN1基因的表达降低锰和锌在肠道的吸收,进而减少锰和锌在组织中的沉积。

Effects of High Dietary Iron on Iron Transporter Gene Expressions in Duodenal Mucosa and Tissue Microelement Contents of Broilers

This experiment was conducted to investigate the effects of dietary iron (Fe) content on tissue some important microelements such as Fe, manganese (Mn), copper (Cu) and zinc (Zn) contents and Fe transporter gene expressions in duodenal mucosa of broilers, and to explore the effects of Fe on absorption and metabolism of microelements of broilers and its mechanism.A total of 336 one-day-old Rose-308 male chicks were randomly divided into 4 groups with 6 replicates per group and 14 chicks per replicate.Chicks in control group were fed a basal diet without adding exogenous Fe (measured value of Fe content was 78 mg/kg), while those in Fe added groups were fed experimental diets added with 100, 250 and 500 mg/kg Fe (FeSO4·7H2O as Fe source) based on the basal diet (measured value of Fe content was 166, 308 and 579 mg/kg, respectively), respectively.The experiment lasted for 21 days.Chicks were slaughtered on 7, 14 and 21 days of age to analyze the contents of Fe, Mn, Cu and Zn in liver, heart, pancreas, duodenal mucosa and tibia ash and the mRNA expression levels of divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1) in duodenal mucosa.The results showed as follows: 1) chicks in the 500 mg/kg Fe added group had significantly lower average daily gain (ADG) during 1 to 7 days of age and 8 to 14 days of age than that in the other three groups (P<0.10), and chicks in the 250 and 500 mg/kg Fe added groups had significantly lower average daily feed intake (ADFI) during 1 to 7 days of age than that in the other two groups (P<0.10).2) Plasma total iron binding capacity, hemoglobin concentration (except 7 days of age) and hematocrit in whole blood at 7, 14 and 21 days of age were not significantly affected by dietary Fe content (P>0.10).Plasma Fe content and transferrin saturation at 7, 14 and 21 days of age were significantly affected by dietary Fe content (P<0.10), and they were increased as dietary Fe content increasing.3) The content of Fe in heart at 7 and 14 days of age and in liver, duodenal mucosa, pancreas and tibia ash at 7, 14 and 21 days of age was increased as dietary Fe content increasing, while the content of Mn in duodenal mucosa, pancreas and tibia ash was decreased.Zn content in pancreas at 7 days of age was significantly decreased by dietary added Fe (P<0.10), but the contents of Zn in pancreas at 14 and 21 days of age and Cu in each analyzed tissue at 7, 14 and 21 days of age were not affected by dietary added Fe (P>0.10).4) The mRNA expression levels of DMT1 and FPN1 in duodenal mucosa at 7, 14 and 21 days of age were significantly affected by dietary Fe content (P<0.10), and they were decreased as dietary Fe content increasing.These results suggest that high Fe diets may decrease the absorption of Mn and Zn through the down-regulations of DMT1 and FPN1 gene expressions in duodenal mucosa, and then result in the lower depositions of Mn and Zn in tissues of broilers.