title: Influence of dietary cholecalciferol, calcium, and phosphorus on urinary calcium in commercial Leghorn hens.
abstract: An experiment was conducted to determine the influence of various dietary levels of cholecalciferol, Ca, and P on urinary Ca and pH, and on plasma concentrations of inorganic P (Pi) and total Ca (TCa) in commercial Leghorn hens. All hens were fed a layer diet containing 500 ICU of cholecalciferol/kg for 30 days and then allocated equally to treatment diets. Twelve treatment diets were in a 3 x 2 x 2 factorial arrangement that comprised three levels of cholecalciferol (0, 2,200, and 4,400 ICU/kg), two Ca levels (3.75 and 5.75%) and two P levels (.3% and .7%). After 9 days of feeding, blood (12 hens per time per treatment) and urine (6 hens per time per treatment) were sampled at 8 and 16 h after oviposition. Urinary Ca and plasma TCa concentrations increased (P less than .05) when dietary cholecalciferol level was increased from 0 to 2,200 ICU/kg, but did not change when cholecalciferol was increased from 2,200 to 4,400 ICU/kg. High levels of dietary Ca elevated (P less than or equal to .05) the urinary Ca concentration of hens fed the low-P treatments. Low levels of dietary P reduced plasma P and increased urinary Ca and pH at all levels of cholecalciferol and Ca; however, the magnitude of increases in urinary Ca were not uniform across all levels of cholecalciferol and Ca. Increases in urinary Ca resulting from low dietary P were relatively small when the diet lacked cholecalciferol, but was increased three- to fourfold when the diet contained adequate or excess levels of Ca and excess but not toxic levels of cholecalciferol.
authors.affiliation: Department of Poultry Science, Auburn University, Alabama 36849.
authors.forename: S K
authors.initials: SK
authors.lastname: Rao
authors.forename: D A
authors.initials: DA
authors.lastname: Roland
authors.forename: J I
authors.initials: JI
authors.lastname: Orban
mesh_terms: D000818:Animals; D002118:Calcium / Q000097:blood / Q000652:urine*; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000494:pharmacology*; D002645:Chickens / Q000378:metabolism* / Q000652:urine; D002762:Cholecalciferol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D010058:Oviposition; D016226:Phosphorus, Dietary / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D002136:Calcium, Dietary; D016226:Phosphorus, Dietary; D002762:Cholecalciferol; D002118:Calcium