关键词: 肉鸡, 磷, 吸收, Na/Pi-Ⅱb, 外翻肠囊法

Abstract: 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 (P<0.01) and jejunum tail (P>0.05) of 60 days broilers. Whereas, higher dietary Pi (TP 0.8% and TP 1.0%) decreased duodenal (P<0.01), jejunum forepart and jejunum tail (P>0.05) 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.

Key words: broiler, phosphorus, absorption, Na/Pi-Ⅱb, everted gut sac