日粮磷水平对肉鸡磷代谢及Na/Pi-Ⅱb基因mRNA表达的影响

Effects of Dietary Phosphorus on Phosphorus Metabolism and Regulation of Sodium-dependent Phosphate Transporter mRNA for Broilers

本论文旨在探讨不同磷水平对肉鸡磷代谢及小肠Na/Pi-Ⅱb(钠依赖Ⅱb型磷转运载体蛋白)基因mRNA表达的影响。选择60日龄体质量约1.5 kg的三黄肉鸡40只,随机分配至日粮总磷水平分别为0.4%(A组)、0.6%(B组)、0.8%(C组)和1.0%(D组)(钙∶有效磷=2∶1)的4个处理中,每个处理设5个重复,每个重复2只鸡(1个代谢笼),其中B处理为对照组。试验结果表明,血清磷随日粮磷水平提高而升高,血清钙随日粮磷水平提高而下降;日粮总磷水平在0.8%时,血清AKP活性最低,而钙磷代谢率最高;与对照组相比,较低磷(TP 0.4%)提高肉鸡空肠前段(P<0.01)和空肠后段(P>0.05)Na/Pi-Ⅱb mRNA表达水平,而高磷(TP 0.8%,TP 1.0%)则降低肉鸡十二指肠(P<0.01)、空肠段(P>0.05)Na/Pi-Ⅱb mRNA表达水平;十二指肠和空肠前段对磷的吸收率随饲粮磷水平的提高而下降,各肠段对磷的体外吸收率在较低磷(TP 0.4%)时最高。结果提示,低磷日粮条件下,提高日粮磷水平可上调Na/PiⅡ-b mRNA表达量,促进磷的吸收,日粮磷水平过高时,则抑制Na/PiⅡ-b mRNA表达。

To study effects of dietary phosphorus on phosphorus metabolism and Na/Pi-Ⅱb mRNA expression in intestine of broilers.Forty 60-day-old broilers with an average initial weight of about 1.5 kg were allotted to four treatments randomly,each treatments had five replicates of two broilers.Levels of dietary total phosphorus were： group A：0.4%,group B：0.6%,group C：0.8% and group D：1.0%（all with calcium∶phosphorus rations of 2∶1）,group B was as control group.The results showed that serum phosphorus level increased as dietary phosphorus increased while serum calcium level decreased.At the 0.8% level of dietary phosphorus,the activity of alkaline AKP tended to be decreased significantly,but the metabolic rate of Ca and Pi were the highest,respectively.Compared with control group,low Pi diet（TP 0.4%） increased expression of Na/Pi-Ⅱb mRNA in jejunum forepart（P0.01） and jejunum tail（P0.05） of 60 days broilers.Whereas,higher dietary Pi（TP 0.8% and TP 1.0%） decreased duodenal（P0.01）,jejunum forepart and jejunum tail（P0.05） expression of Na/Pi-Ⅱb mRNA.Phosphorus uptakes from feedstuffs of broiler dissimilar small intestine were measured by everted gut sac.The result showed： the absorption rate of phosphorus in vitro of duodenum and jejunum forepart declined as dietary phosphorus increased,and the absorption rate of phosphorus in vitro of each intestinal segment respectively was highest at lower Pi diet（TP 0.4%）.The result implies that increasing dietary phosphorus levels could increase expression of Na/Pi-Ⅱb mRNA and phosphorus absorption at low Pi diet,whereas the exorbitant dietary phosphorus levels inhibit its expression.