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 Title: Manganese utilization as affected by excess calcium and phosphorus Author(s): Wedekind, Karen J. Doctoral Committee Chair(s): Baker, David H. Department / Program: Animal Sciences Discipline: Animal Sciences Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Agriculture, Animal Culture and Nutrition Health Sciences, Nutrition Abstract: Different experimental approaches were undertaken to evaluate the effect of excess Ca and P on Mn utilization. Chick bioassays were conducted to assess the effects of various sources and varying levels and combinations of excess dietary Ca and P on Mn bioavailability. The regression of total tibia Mn on supplemental Mn intake was done according to a standard curve procedure in the first set of experiments, and a slope-ratio multiple-regression approach was used in the second set of experiments. Feeding.88% excess P, regardless of source and irrespective of whether fed alone or in combination with excess Ca, reduced Mn utilization by 50 to 65%. Calcium sources caused only slight reductions (ie., 0 to 15%) in Mn utilization. Relative to the standard (no added P).22,.44 and.88% excess P reduced Mn utilization by 16, 22, and 31%, respectively, in a second set of experiments. Total tibia Mn was not depressed by excess Ca in these trials. A repletion-depletion assay was conducted to evaluate the effect of excess P and Mn status on Mn excretion and turnover. Chicks were fed either 30 mg Mn/kg or 1000 mg Mn/kg in casein-dextrose diets for 7 d. Following this loading period, birds were fed a Mn-deficient casein-dextrose diet (1.4 mg Mn/kg) in the presence or absence of.5% excess P supplied from dicalcium phosphate. Changes in whole body and selected body-tissue Mn were determined over the 20-d depletion period. All tissues showed significantly reduced biological half-lives as a result of increased Mn status, but were not affected by excess P. To evaluate the effect of excess Ca or P on endogenous fecal Mn excretion and true Mn absorption, two balance studies with growing chicks were conducted. An isotope-dilution technique utilizing $\sp{54}$Mn, was used to estimate endogenous Mn in excreta. True absorption of Mn was not affected by excess Ca but was adversely affected by excess P. In birds fed 137 mg Mn/kg, absorption of Mn decreased 22% as excess P increased from 0 to.8%, whereas in birds fed 1037 mg Mn/kg, absorption of Mn decreased 59% as P level increased. The above results indicate that Mn utilization is not affected by excess Ca but is markedly reduced by excess dietary P. Issue Date: 1990 Type: Text Language: English URI: http://hdl.handle.net/2142/20866 Rights Information: Copyright 1990 Wedekind, Karen J. Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9114455 OCLC Identifier: (UMI)AAI9114455
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