title: Correlation of biological value of feed phosphates with their solubility in water, dilute hydrogen chloride, dilute citric acid, and neutral ammonium citrate.
abstract: Relative biological values (BV) of 36 feed phosphates were determined with female turkeys in bioassays of 21-day duration using three response criteria: weight gain, tibia ash percentage, and gain:feed ratio. Calcium phosphate, dibasic dihydrate (United States Pharmacopeia) was the reference standard. Nine mono-dicalcium phosphates (M-DCP, 21.0% phosphorus), 13 di-monocalcium phosphates (D-MCP, 18.5% phosphorus), and 14 defluorinated phosphates (DFP, 18.0% phosphorus) were evaluated. The average relative BV for M-DCP, D-MCP, and DFP samples were 97.6, 94.6, and 90.8%, respectively. Solubility of phosphates was determined by four recognized methods. The solvents were water, .4% HCl, 2.0% citric acid (CA), and neutral ammonium citrate (NAC). Water solubility of M-DCP samples was greater (67.5%) than that of D-MCP (38.8%) and DFP (8.9%) samples. Correlation of water solubility of phosphates to their relative BV was quite low, and water solubility was a poor indicator of BV. When .4% HCl was the solvent, correlation coefficients (r) were .55, .33, and .72 for M-DCP, D-MCP, and DFP, respectively. Based on these results and prediction equations, .4% HCl solubility would be inappropriate for estimating BV of M-DCP and D-MCP samples. Solubility of feed phosphates (mainly D-MCP and DFP) in 2.0% CA or NAC was positively correlated with BV; the r values were .87 to .95. Both of these solubility tests provided a good index of BV. However, it would seem inappropriate and risky to replace bioassays totally with these tests. Feed phosphate users could perform either the 2.0% CA or NAC solubility test easily as a screen for BV along with other quality control procedures (i.e., phosphorus, calcium, sodium, and fluoride determinations).
authors: Department of Animal Science, University of Nebraska, Lincoln 68583-0908.
authors: T W
authors: TW
authors: Sullivan
authors: J H
authors: JH
authors: Douglas
authors: N J
authors: NJ
authors: Gonzalez
authors: P L
authors: PL
authors: Bond
mesh_terms: D000821:Animal Feed; D000818:Animals; D001682:Biological Availability; D002951:Citrates; D019343:Citric Acid; D005260:Female; D006851:Hydrochloric Acid; D010710:Phosphates / Q000737:chemistry* / Q000493:pharmacokinetics*; D012995:Solubility; D014422:Turkeys / Q000378:metabolism*; D014867:Water; D015430:Weight Gain
chemical_list: D002951:Citrates; D010710:Phosphates; D014867:Water; D019343:Citric Acid; D006851:Hydrochloric Acid