| Phosphorus is one of mineral elements which contented much in animal body, the body requires that amounts are next only to calcium, occupies important position in animal growth. At the same time, as a rare element in nature, phosphorus is one of the most expensive composing in feedstuffs. But almost over 70% TP couldn't be utilized by animals which reflect on environment badly. Therefore, rational and effective use of phosphorus will quite benefit to retrench resource, debase feeding cost and decrease phosphorus pollution. This study was to investigate effects of diverse dietary phosphorus on phosphorus metabolism and to determine the regulation mechanism of Na/Pi-â…¡b cotransporter gene expression.In Exp.1, the effects of diverse dietary phosphorus on the activities of alkaline phosphatase (AKP) in the serum, serum phosphorus and calcium levels and nutrients metabolic rate of diet were evaluated using forty 60-day-old broilers with an average initial weight of about 1.5 Kg, which were allotted to four treatments randomly, each treatments has five replicates of two broilers (in the same metabolism cage). Levels of dietary phosphorus were:0.4%,0.6%,0.8% and 1.0% (all with calcium:phosphorus rations of 2:1), grope 0.6% was the matched grope. The experimental results showed that serum phosphorus level increased as dietary phosphorus increased but serum calcium level and the metabolic rate of CF decreased as dietary phosphorus increased(P<0.01). At the 0.8% level of dietary phosphorus, the activity of alkaline AKP and the metabolic rate of EE tended to be decreased significantly by 89.8% and 2.6%; however, the metabolic rate of Ca, Pi and DM were the highest respectively, increasing 30.78%,6.57% and 0.67% compared with the matched grope.In Exp.2, the samples from Exp.1 were adopted in this trial which was cranked out as duodenum, jejunum forepart, jejunum tail and ileum. And the trial was to study effects of dietary phosphorus on intestinal abundance of Na/Pi-â…¡b mRNA. And the Na/Pi-â…¡b mRNA abundance was determined by real-time RT-PCR. Results showed: compared with matched grope, low Pi diet (TP 0.4%) increased Na/Pi-IIb mRNA abundance in jejunum forepart (P<0.01) and jejunum tail (P>0.05) of 60 days broilers. Whereas, higher dietary Pi (TP 0.8%, TP 1.0%) decreased duodenal (P<0.01),jejunum forepart and jejunum tail (P>0.05) Na/Pi-â…¡b mRNA abundance in 60 days broilers. However, there has no obvious law in Na/Pi-â…¡b mRNA expression following the intestines change by the same Pi level.In Exp.3, phosphorus uptakes from feedstuffs of broiler dissimilar small intestine were measured by everted gut sac. Sacs of duodenum, jejunum forepart, jejunum tail and ileum from 20 broilers at the age of 60 days were random distributioned to five treatments, each treatment was assigned four replicate, one replicate was assigned one sac. These treatments include the matched grope and 4 diets which were rationing in Exp.1 having the levels of dietary phosphorus 0.4%,0.6%,0.8% and 1.0% respectively. The result showed:the absorption rate of phosphorus in vitro of duodenum and jejunum forepart declined as dietary phosphorus increased, whenas the jejunum tail's changed unconspicuous accordingly. The absorption rate of phosphorus in vitro of each intestinal segment respectively was highest at lower Pi diet (TP 0.4%).Overall Conclusions:When the low phosphorus diet, increasing dietary phosphorus levels can increase the abundance of Na/Pi-â…¡b mRNA, whereas the exorbitant dietary phosphorus levels inhibit its expression. Low phosphorus diet can increase phosphorus absorption. |
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