Study On Optimal Addition Of 25-hydroxycholecalciferol Into A Dietary Of Broiler Chickens

Vitamin D3 is used as a feed additive in regulating calcium(Ca)and phosphorus(P)metabolism in animals for many years.It undergoes 25-hydroxylation in the liver to transport 25-hydroxycholecalciferol(25-OH-D3).The commercial 25-OH-D3 has been produced and approved for use in poultry and swine feed in China in 2013.The relative bioavailability of 25-OH-D3 was greater than that of vitamin D3.Three experiments were conducted to investigate the requirement of dietary 25-OH-D3 for broiler chickens from 1 to 42 days of age.Experiment 1 Effects of Vitamin D Dificiency on Growth Performance,Bone Mineralization,and Calcium and Phosphorus Retention in Broiler Chickens at Different Growth StagesThis experiment was conducted to evaluate vitamin D dificiency on growth performance,bone mineralization,and Ca and P retention in broiler chickens at different growth stages.A 2×2 factorial experiment was designed to test two levels of vitamin D3(0 and 1 000 IU/kg)and two-phase(days 1 to 20,starter phase;days 21 to 40,grower phase).100 female Ross 308 broilers at one day of age and 100 broilers at 21 days of age were randomly assigned two treatments with five replicates of ten birds per replicate.Vitamin D3 levels were 0 and 1000 IU/kg.On day 5,10,15,20,25,30,35,and 40,five birds were killed.Compared with the bird fed diets with 1000 IU/kg vitamin D3,vitamin D dificiency decreased body weight gain and feed intake of broilers from 1 to 20 and 21 to 40 days of age(P<0.05).Vitamin D dificiency decreased plasma inorganic phosphate(Pi)concentration at 20 days of age(P<0.05).Vitamin D dificiency declined the weight,length,ash weight,and percentage contents of ash,Ca,and P in the femur,tibia,and metatarsus at 20 and 40 days of age(P<0.05).Vitamin D dificiency also decreased the Ca and P retention in birds from 11 to 14 and 31 to 34 days of age(P<0.05).These data indicate that vitamin D dificiency damages growth performance and bone mineralization of broiler chickens especially at 1 to 20 days of age.Experiment 2 Study On Optimal Addition of 25-Hydroxycholecalciferol(25-OH-D3)Into a Dietary of Broiler ChickensThis experiment was conducted to investigate the requirement of 25-OH-D3 for broiler chickens from 1 to 42 days of age.A single factor completely randomize design was used.A total of 500 one-day-old male birds were randomly assigned to ten groups with five replicates per group and ten birds per replicate.The birds were fed the basal mash diet containing 25-OH-D3 at the levels of 50,100,200,400,600,800,1 600,2 400,3 200 and 4 000 IU/kg.The body weight gain(BWG)and feed intake(FI)increased but the feed conversion ratio(FCR)and mortality decreased when dietary 25-OH-D3 levels increased from 50 to 600 IU/kg in broiler chickens from 1 to 42 days of age(P<0.05).No differences in growth performance were observed when dietary 25-OH-D3 level increased from 600 to 4 000 IU/kg(P>0.05).The bone(femur,tibia,and metatarsus)breaking-strength,weight,length,ash weight,and the percentages of ash content,Ca content,and P content linearly increased when dietary 25-OH-D3 levels increased from 50 to 600 IU/kg in broilers at 21 and 42 days of age(P<0.05).No differences in bone mineralization were found when the 25-OH-D3 levels increased from 600 to 4 000 IU/kg(P>0.05).Plasma calcium concentration also increased when dietary 25-OH-D3 levels increased from 50 to 600 IU/kg(P<0.05).Plasma Pi concentration was not affect by the dietary 25-OH-D3 level(P>0.05).The retention rate of Ca and P increased when dietary 25-OH-D3 levels increased from 50 to 800 IU/kg in broilers from 11 to 14 and 31 to 34 days of age(P<0.05).In conclusion,the requirement of dietary 25-OH-D3 is 476 IU/kg in broiler chickens from 1 to 21 days of age and 448 IU/kg in birds from 22 to 42 days of age based on broken-line model analysis using the growth performance and bone mineralization as criteria.Experiment 3 Comparison in Growth Performance and Bone Mineralization between the Optimal Level and Commercial Level of 25-Hydroxycholecalciferol in Broiler ChickensThis experiment was conducted to compare the optimal level and commercial level of 25-hydroxycholecalciferol in broiler chickens from 1 to 42 days of age.A total of 240 one-day-old male broilers were assigned to four groups with six replicates per group and ten birds per replicate.Diet 1 was the control diet with 1 000 IU/kg vitamin D3.Diet 2,3,and 4 were supplemented with 500,1 000,and 2 760 IU/kg 25-OH-D3,respectively.No significant differences in body weight gain,feed intake,and feed conversion ratio were observed in diets 2 to 4 compared with the control diet(P>0.05).Compared with the control diet,no significant differences in weight,length,diameter,ash weight,ash content,Ca content,and P content(except of femur Ca)of femur,tibia,and metatarsus were found in diets 2 to 4(P>0.05).These data indicate that 500 IU/kg 25-OH-D3 is suffient for growth performance and bone mineralization of broiler chickens from 1 to 42 days of age.In conlusion,vitamin D dificiency damages growth performance and bone mineralization of broiler chickens especially at 1 to 20 days of age.The requirement of 25-OH-D3 is 476 IU/kg in broiler chickens from 1 to 21 days of age and 448 IU/kg in birds from 22 to 42 days of age based on broken-line model analysis using the growth performance and bone mineralization as criteria.Compared with the commercial recommendation level(2 760 IU/kg),500 IU/kg 25-OH-D3 is suffient for growth performance and bone mineralization of birds from 1 to 42 days of age.Overall,the optimal 25-OH-D3 level is 500 IU/kg in broiler chickens from 1 to 42 days of age.