Studies On Vitamin D₃and25-Hydroxyvitamin D₃Requirements And Relative Bioavailability In White Pekin Ducks

Two experiments were conducted in this dissertation to investigate the effects of dietary vitaminD₃（VD₃） or25-hydroxyvitamin D₃（25（OH）D₃） levels on growth performance, carcass traits, plasmabiochemical indices and tibial developmental indices of Pekin ducks. The VD₃and25（OH）D₃requirementsas well as their relative bioavailability in Pekin ducks were estimated to provide practical guideline forPekin duck’s production.Experiment1was conducted to determine the effects of dietary VD₃or25（OH）D₃levels on growth ofPekin ducks fed acorn-soybean meal basal diet from1to21days of age. A single factor completelyrandomize design was used.One thousand and two hundred1-d-old male Pekin ducklings from onecommercial hatchery were divided to15treatments. Each treatment consisted of8replicate pens with10birds per pen. Dietary treatments were composed of a basal diet without VD₃and basal diets supplementedwith7levels of vitamin D₃premix or7levels of25（OH）D₃premix according to cholecalciferolactivities of200,400,800,1200,1600,2000, and3000IU/kg.Birds were providedwith ad libitum access to feed andwater with24hours continuous light and killed at21days of age. The body weight （BW）, average dailyweight gain （ADG）, breast meat rate, abdominal fat rate, plasma alkaline phosphatase （ALP） activities,bone weight, bone ash percentage, bone strength, Bone mineral density （BMD）, Bone mineral content（BMC） of Pekin ducks from1to21days of age were all significantly affected by VD₃levels （P <0.05）, butaverage daily feed intake （ADFI）, feed/gain （F/G）, mortality, leg meat rate, plasma Ca and P concentration,bone length, ash Ca and P concentration, ash Ca:P ratio and TD score were not （P>0.05）. Dietary25（OH）D₃levels significantly affected breast meat rate,plasma ALP activities, bone weight, bone ashpercentage, bone strength, BMD, BMCand TD score （P <0.05）. The differences between BW, ADG, ADFI,F/G, mortality, abdominal fat rate, leg meat rate, plasma Ca and P concentration, bone length, ash Ca and Pconcentration and ash Ca:P ratio were not significant （P>0.05）, however. Increasing dietary VD₃or25（OH）D₃levels can reduce TD incidence and severity. During the starter period from1to21days of age,the VD₃requirements of Pekin ducks for ADG, BMD, BMC,bone ash percentage, bone strengthand boneweight were respectively362,422,651,310,499and285IU/kg, while the25（OH）D₃requirement for thesame response criteria were respectively400,527,514,597,342and340IU/kg, by broken line models withquadratic analysis.The bioavailabilityvalues of25（OH）D₃,for plasma Ca concentration, BMD, BMC, boneash percentage, bone strength and TD score, were respectively1.63,0.94,1.44,1.60,1.49and1.5times ascompared to VD₃in Pekin ducks from1to21days of age by slope ratio analysis and calculation, while thebioavailability values for ADG, plasma Ca concentration, BMD, BMC, bone ash percentage, bone strength,bone length and TD score were respectively1.14,4.12,0.68,1.68,1.37,0.98,1.96and1.49times higherthan VD₃by exponential model analysis and calculation.Experiment2was conducted to determine the effects of dietary VD₃or25（OH）D₃levels on growth ofPekin ducks from22to42days of age. A single factor completely randomize design was used.One thousand and two hundred1-d-old male Pekin ducklings from one commercial hatchery were fedacorn-soybean meal basal diet with200IU/kg VD₃to21days of age, then nine hundred and sixty Pekinducks were selected and divided to15treatments. Each treatment consisted of8replicate pens with8birdsper pen. Dietary treatments were the same as Experiment1.Birds were providedwith ad libitum access tofeed and water with12hours continuous light （12L:12D） from22to42days of age. The BW, ADG, ADFI,F/G, mortality and gait score of Pekin ducks from22to35days of age were all significantly affected byVD₃or25（OH）D₃levels （P <0.0001）. During the finisher period from22to35days of age, the VD₃requirement of Pekin ducks for ADG and ADFIwere respectively405and531IU/kg, while the25（OH）D₃requirement for ADG, ADF and F/GIwere respectively371,347and323IU/kg, by broken line models withquadratic analysis. Dietary VD₃levelssignificantly affected BW, ADG, ADFI, F/G, mortality, gaitscore,breast meat rate,sebum rate, liver rate, eviscerated weight, plasma ALP activities, plasma Ca and Pconcentration, bone weight, bone length, bone ash percentage, bone strength, BMD and BMCof Pekinducks from22to42days of age （P <0.05）, but not leg meat rate, abdominal fat rate, ash Ca and Pconcentration, ash Ca:P ratio and TD score （P>0.05）. Dietary25（OH）D₃levelssignificantly affected BW,ADG, ADFI, F/G, mortality, gait score,breast meat rate,sebum rate, liver rate, eviscerated weight, plasmaALP activities, plasma Ca and P concentration, bone weight, bone length, bone ash percentage, ash Ca andP concentration, ash Ca:P ratio, bone strength, BMD and BMC （P <0.05）. The differences between legmeat rate, abdominal fat rate and TD score were not significant （P>0.05）, however.During the finisherperiod from22to42days of age, the VD₃requirements of Pekin ducks for ADG, breast meat rate,plasmaCa concentration, plasma ALP activities, BMD, BMC,bone ash percentage, bone strengthand bone weightwere respectively362,338,377,325,673,739,324,681and750IU/kg, while the25（OH）D₃requirementfor ADG, F/G, breast meat rate,plasma Ca concentration, plasma ALP activities, bone ash percentageandbone weight were respectively316,256,260,213,273,209and486IU/kg, by broken line models withquadratic analysis.The bioavailabilityvalues of25（OH）D₃,for ADG, bone ash percentage, ash Caconcentration,and plasma ALP activities, were respectively1.55,0.91,1.28and1.84times as compared toVD₃in Pekin ducks from22to42days of age by slope ratio analysis and calculation, while thebioavailability values for ADG, breast meat rate, plasma Ca concentration,plasma ALP activities, boneweight, bone ash percentage and ash Ca concentration were respectively1.39,1.24,3.48,1.40,2.36,1.89and1.25times higher than VD₃by exponential model analysis and calculation.In conclusion, Vitamin D deficiency as well as light shortage may lead to growth inhibition and poortibial developmental qualities of Pekin ducks. Supplementation in diet with VD₃or25（OH）D₃can bothimprovegrowth performance and carcass traits, and promote tibial development of Pekin ducks as well.TheVD₃and25（OH）D₃requirements of Pekin ducks from1to21days of agefor bone strength are499and342IU/kgby broken line models with quadratic analysis, respectively. The VD₃and25（OH）D₃requirementsof Pekin ducks from22to42days of age for BMC and ADG are731and316IU/kg, respectively.Thebioavailability valueof25（OH）D₃for bone strength is1.44times as compared to VD₃in Pekin ducks from1to21days of age, while for ADG the value is1.37timeshigher than VD₃in Pekin ducks from22to42days of age, by exponential model analysis and calculation. Overall, the bioavailability values of25（OH）D₃aregenerally higher than VD₃.