title: Interaction between dietary 1,25-dihydroxycholecalciferol and calcium and effects of management on the occurrence of tibial dyschondroplasia, leg abnormalities and performance in broiler chickens.
abstract: 1. Two experiments were performed to compare the relative effectiveness of feeding 1,25-dihydroxycholecalciferol (1,25-DHCC) in minimising leg abnormalities in broilers with other methods and to investigate interactions between dietary 1,25-DHCC and calcium. 2. Adding 5 micrograms 1,25-DHCC/kg to a diet containing 12 g calcium/kg was more effective than early food restriction or meal feeding in preventing leg abnormalities but was found to cause a growth depression. 3. The second experiment, which had a factorial design, with diets containing 7.5, 10.0 and 12.5 g calcium and 0, 2.0, 3.5 and 5.0 micrograms 1,25-DHCC/kg, showed linear and quadratic interactions between these dietary factors. Diets with higher concentrations of both 1,25-DHCC and calcium resulted in growth depression associated with hypercalcaemia. 4. The incidence of tibial dyschondroplasia (TD) at 3 weeks of age was highest with the basal diet containing 7.5 g calcium/kg and was markedly reduced by addition of 1,25-DHCC and/or calcium. The incidence was very low or non-existent when 1,25-DHCC was fed at 3.5 micrograms/kg or greater. 5. Feeding 5 micrograms/kg 1,25-DHCC had no effect on plasma 1,25-DHCC concentrations, although at the higher dietary calcium contents plasma concentrations of 25-hydroxy- and 24,25-dihydroxy-cholecalciferol were lower in those birds fed 1,25-DHCC. 6. It is concluded that 1,25-DHCC is most effective in preventing TD without accompanying growth depression when it is fed in conjunction with diets containing less than 10 g calcium/kg.
authors.affiliation: Roslin Institute (Edinburgh), Midlothian, England.
authors.forename: J S
authors.initials: JS
authors.lastname: Rennie
authors.forename: H A
authors.initials: HA
authors.lastname: McCormack
authors.forename: C
authors.initials: C
authors.lastname: Farquharson
authors.forename: J L
authors.initials: JL
authors.lastname: Berry
authors.forename: E B
authors.initials: EB
authors.lastname: Mawer
authors.forename: C C
authors.initials: CC
authors.lastname: Whitehead
mesh_terms: D000821:Animal Feed; D000822:Animal Husbandry; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002117:Calcitriol / Q000378:metabolism / Q000627:therapeutic use*; D002118:Calcium / Q000378:metabolism*; D002645:Chickens; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004734:Energy Metabolism / Q000187:drug effects; D005121:Extremities; D010009:Osteochondrodysplasias / Q000378:metabolism / Q000517:prevention & control / Q000662:veterinary*; D011201:Poultry Diseases / Q000378:metabolism / Q000517:prevention & control*
chemical_list: D002117:Calcitriol; D002118:Calcium