Effect Of Dietary Supplemental Vitamin D₃ On Phosphorus Absorption And Utilization And Gene Expressions Of Related Phosphate Transporters Of Broilers

The effect of dietary supplemental Vitamin D3(VD3)on phosphorus(P)absorption and utilization as well as its possible mechanism of broilers were studied by the following two experiments.Experiment 1.Effect of dietary supplemental VD3 levels on bone phosphorus retention and utilization of broilersA completely randomized factorial design involving 2 non-phytate phosphorus(NPP)contents [0.45%(normal P)and 0.23%(P deficiency)(the analyzed values were 0.44% and 0.21%,respectively)]× 4 VD3 supplemental levels(0,1000,2000,and 4000 IU/kg).There were a total of 8 treatments with 6 replicate cages of 10 one-day(d)-old AA male broilers per cage for each treatment.The experiment lasted for 21 d.The results showed that the broilers fed diets containing 0.44% NPP level had higher(P<0.0001)average daily gain(ADG),average daily feed intake(ADFI),tibia ash content and its phosphorus content,while had lower(P<0.0007)feed/gain(F/G)and tibia ash phosphorus absolute retention rate compared with the broilers fed diets containing 0.21% NPP level.Dietary supplemental VD3 significantly enhanced(P<0.005)ADG,ADFI,tibia ash content and its phosphorus absolute retention rate of broilers,significantly decreased(P<0.003)F/G of broilers compared to the group without addition of VD3.The interaction between NPP levels and VD3 levels significantly affected(P<0.04)the mortality of broilers from 1 to 21 d of age.When the broilers fed diets containing 0.44% NPP level,dietary supplemental VD3 did not affect(P>0.60)the mortality of broilers compared to the group without addition of VD3,however,when the broilers fed diets containing 0.21% NPP level,supplemental VD3 significantly decreased(P<0.02)the mortality of broilers compared to the group without addition of VD3.Experiment 2.Effect of dietary supplemental VD3 levels on P absorption and utilization and m RNA expression levels of P transporters of broilersA completely randomized factorial design involved 2 NPP contents [0.45%(normal P)and 0.23%(P deficiency)(the analyzed values were 0.43% and 0.22%,respectively)]×2 VD3 supplemental levels(0 and 3500 IU/kg).There were a total of 4 treatments with 8 replicate cages of 12 one-d-old AA male broilers per cage for each treatment.The experiment lasted for 22 d.The results showed that the broilers fed diets containing 0.43% NPP level had higher(P<0.009)ADG,ADFI,P contents in plasma from portal vein blood after feeding for 2 h or 6 h and 10 h fasting as well as m RNA expression level of Pi T-2 in the duodenum,while had lower(P<0.0001)tibia ash P absolute retention rate and m RNA expression levels of type IIb sodium-dependent phosphate cotransporter(Na P-IIb)in the duodenum and jejunum compared with the broilers fed diets containing 0.22% NPP level.Dietary supplemental VD3 significantly enhanced(P<0.03)tibia ash P absolute retention rate and m RNA expression level of inorganic phosphate transporter 2(Pi T-2)in the jejunum of broilers compared to the group without addition of VD3.The interaction between NPP levels and VD3 levels significantly affected(P<0.03)the mortality,P contents in plasma from portal vein blood after feeding for 4 h,tibia ash content,tibia ash P content and m RNA expression level of Na P-IIb in the ileum and m RNA expression levels of inorganic phosphate transporter 1(Pi T-1)in the duodenum and jejunum of broilers.When the broilers fed diets containing 0.43% NPP level,dietary supplemental VD3 did not affect(P>0.36)the above 6 indices,however,when the broilers fed diets containing 0.22% NPP level,dietary supplemental VD3 significantly increased(P<0.02)P content in plasma from portal vein blood after feeding for 4 h,tibia ash content,tibia ash P content and m RNA expression level of Na P-IIb in the ileum,significantly decreased(P<0.05)the mortality,m RNA expression levels of Pi T-1 in the duodenum and jejunum of broilers compared to the group without addition of VD3.In conclusion,dietary supplemental VD3 enhanced the growth performance and decreased the mortality of P-deficient broilers,as well as promoted P absorption in intestine and P retention and utilization in bone by increasing m RNA expressions of Na P-IIb and Pi T-2 and decreasing m RNA expression of Pi T-1 in the small intestine of P-deficient broilers.These results would be of very important theoretical and practical significance for providing a nutritional strategy to promote P absorption and utilization and thus reduce the dietary inorganic P addition and environmental pollution caused by P emissions by supplemental VD3 in broiler production.