Effects Of 1?-hydroxycholecalciferol On Growth Performance,Bone Mineralization,Plasma Biochemical Parameters,and MRNA Of Sodium-dependent Phosphate Cotransporter In Small Intestine Of Broiler Chickens

The relative bioavailability?RBV?of 1?-hydroxycholecalciferol?1?-OH-D₃?to cholecalciferol?VD₃?and the effects of of 1?-OH-D₃ levels on growth performance,bone mineralization,and mRNA expression of 25-hydroxylase in liver and sodium phosphate cotransporter in small intestine and kidney in 1-to 21-d-old broiler chicks fed with calcium?Ca?-and phosphorus?P?-deficient diets were studied in our research.This study aims to discuss whether 1?-OH-D₃ promote the absorption of inorganic phosphorus?Pi?,which relates to the decrease of dietary phosphorus levels,and reducing environmental phosphorus pollution.Experiment 1 Comparison of Bioavailability of 1?-Hydroxycholecalciferol and Cholecalciferol in Broiler Chicken DietsThe 400 male of 1-d-old Ross 308 broilers used in the experiment were weighted at 1 d,and all had a similar weight.All chicks were randomly assigned to 8 treatments with 5 replicates each.Eight test diets were designed in this study.Five levels of D₃?0,2.5,5,10,and 20 ?g/kg?and three levels of 1?-OH-D₃?1.25,2.5,and 5 ?g/kg?were added to a basal diet.The basal diet contained 0.50% Ca and 0.25% non-phytate phosphorus?NPP?,without D₃.The relative bioavailability?RBV?of 1?-OH-D₃ to D₃ was determined by the slope ratio method.Results as follows:?1?1?-OH-D₃ or VD₃ linearly increased body weight gain?BWG?,feed intake?FI?,plasma Ca?P<0.05?;the weight,length,width,ash weight and content,and Ca and P content of tibia,femur and metatarsus responded linearly to 1?-OH-D₃ or VD₃ levels?P<0.05?.?2?Using body weight gain,feed intake,and plasma Ca as criteria,the RBV of 1?-OH-D₃ to D₃ were 4.78,4.75,and 4.21,respectively.Using tibia weight,length,width,ash weight and content,and Ca and P content as criteria,the RBV of 1?-OH-D₃ to D₃ were 5.58,5.16,4.42,4.70,5.03,4.46,4.70,and 4.79.Using femur weight,length,width,ash weight and content,and Ca and P content as criteria,the RBV of 1?-OH-D₃ to D₃ were 5.09,4.43,3.19,5.83,5.21,5.27,and 5.31.Using metatarsus weight,length,width,ash weight,and Ca content as criteria,the RBV of 1?-OH-D₃ to D₃ were 5.00,4.05,5.94,4.73,and 5.64.These data indicate that the RBV of 1?-OH-D₃ to D₃ is 4.83 in promoting growth performance and bone mineralization in broilers from 1 to 21 d of age.?3?These data indicate that the RBV of 1?-OH-D₃ to D₃ is 4.83 in promoting growth performance and bone mineralization in broilers from 1 to 21 d of age.Experiment 2 Influence of the Levels of 1?-Hydroxycholecalciferol on Growth,Bone Mineralization,and mRNA Expression of Sodium Phosphate Cotransporter in Small Intestine of ChicksThe 250 male of 1-d-old Ross 308 broilers used in the experiment were weighted at 1 d,and all had a similar weight.All chicks were randomly assigned to 5 treatments with 5 replicates each.A basal diet?Table 1?was formulated to contain suboptimal concentrations of Ca?0.50%?and NPP?0.25%?,without D₃.Four levels of 1?-OH-D₃?0,1.25,2.5,and 5 ?g/kg?were added to the basal diet.Meanwhile,the positive control was designed containing 1.00% Ca,0.45% NPP,and 25 ?g/kg vitamin D₃.The date of performance was recorded during the 21-d experiment.on day 21,a chicken weighing close to the average weight of the replicate was selected and killed for collection of blood,bones,tissues of liver,kidney,and small intestine.Primer sets were designed using software?Primer Premier 5.0?for the examination of gene expression by Real-time PCR.Results as follows:?1?The levels of 1?-OH-D₃?0,1.25,2.5 and 5 ?g/kg?improved BWG,FI,feed efficiency?FE?,utilization and retention of Ca and t P of broilers from 1 to 21 days of age?P<0.05?;broilers fed with basal diets supplemented with 5 ?g/kg 1?-OH-D₃ exhibited equal growth performance compared with the birds fed with control diets?P>0.05?.?2?The levels of 1?-OH-D₃?0,1.25,2.5 and 5 ?g/kg?increased plasma Ca and Pi?P<0.05?,decreased plasma alanine aminotransferase?ALT?,aspartate aminotransferase?AST?,lactate dehydrogenase?LDH?,creatinine?CRE?,and total protein?TP??P<0.05?of broilers.?3?The levels of 1?-OH-D₃?0,1.25,2.5 and 5 ?g/kg?increased the tibia and femur weight,length,width,ash weight and content,and Ca and P content of broilers?P<0.05?;the tibia and femur in birds fed the basal diet supplemented with 5 ?g/kg 1?-OH-D₃ were able to achieve the same weight and ash content values as chicks fed the control diets?P>0.05?.?4?The levels of 1?-OH-D₃?0,1.25,2.5 and 5 ?g/kg?up-regulate the mRNA expression of 25-hydroxylase in liver and nuclear vitamin D receptor?n VDR?,type ?b sodium phosphate cotransporter?Na Pi-?b?,protein kinase C?PKC? and PKC??in small intestine?P<0.05?.The levels of 1?-OH-D₃ increased kidney n VDR mRNA levels?P<0.05?,and there was a trend for increasing the mRNA expression of type ?a sodium phosphate cotransporter?Na Pi-?a?and type ?c sodium phosphate cotransporter?Na Pi-?c?in kidney.No significant differences were observed in the mRNA expression of 25-hydroxylase,n VDR,Na Pi-?a,Na Pi-?b,Na Pi-?c,PKC? and PKC? between the birds fed 5 ?g/kg 1?-OH-D₃ and the birds fed the control diets.