Bioavailability of Phosphorus in Commercial Phosphate Supplements for Turkeys

Abstract

Forty-seven commercial phosphorus supplements were obtained from feed manufacturers and subjected to biological phosphorus availability assay using the turkey poult. Bone ash was the response criterion. Compared to a reference source of commercial mono/ dicalcium phosphate (assigned 100), 7 other mono/ dicalcium phosphates averaged 97.1 (range 88.6 to 110.0), 20 dicalcium phosphate sources averaged 90.6 (76.3 to 104.8), and 20 defluorinated phosphate sources averaged 78.4% (68.6 to 89.6) availabilities. Combining equal parts of all sources of each type of phosphorus supplement and using purified grade calcium phosphate monobasic monohydrate as a defined standard, the commercial mono/ dicalcium phosphates, dicalcium phosphates, and defluorinated phosphates averaged (with 95% confidence limits) 93.6 +/- 7.6, 88.3 +/- 8.2, and 70.2 +/- 7.2% phosphorus availability in a slope ratio bioassay. Calculating the requirement intercepts utilizing the blended phosphorus supplements indicated apparent requirements using mono/ dicalcium phosphate, dicalcium phosphate, and defluorinated phosphate of .74, .76, and .83% total phosphorus in the diet, respectively. Considering 1) the variability in availability of the sources, 2) variation in feed mixing, 3) the National Research Council requirement of .80%, and 4) that newly hatched poults are completely dependent on one batch of prestarter feed during 0 to 10 days of life, it is suggested that in certain instances field rickets could result from deficiency of dietary phosphorus.

Biological Values of Phosphorus from Various Sources for Young Turkeys

“…Commercial defluorinated phosphates were only 86% as biologically effective as the dicalcium phosphates. Waibel et al (1984) reported similar results. With the biological value of 7 monocalcium and dicalcium phosphates (21% P) set at 100%, they reported that the average biological values of 20 dicalcium phosphates (18.5%) and of 20 defluorinated phosphates were 93 and 81%, respectively.…”

“…Other researchers have also used this compound as a standard (Wilcox et al, 1955;Hurwitz, 1964) or have used reagent grade monocalcium phosphate monohydrate (Motzok et al 1956;Waibel et al 1984). These hydrated compounds are highly utilized and provide a better standard for attainment than 3-tricalcium phosphate.…”

“…Thus, the results of our study provided an equally or more sensitive bioassay than those of other researchers. The slope ratio bioassay (Finney, 1978) has been the analysis of choice for determining the relative biological value of different phosphorus sources (Hurwitz, 1964;Waibel et al, 1984). However, a plot of either body weight, bone ash, or toe ash on level of added phosphorus results in exponential curves rather than linear lines.…”

“…Differences in relative biological values among commercial phosphorus sources have been reported (Nelson and Walker, 1964;Edwards, 1968;Pensack, 1974;McGillivray, 1978;Waibel et al, 1984). In general, the monocalcium phosphates tend to have a higher relative biological value than do the dicalcium phosphates, and the latter tend to have a greater relative biological value than do the defluorinated phosphates.…”

Bioavailability of Phosphorus in Poultry Litter Biomass Ash Residues for Turkeys

“…Other experimental details were as those reported by Waibel et al (1983). The basal assay diet was a corn-soybean meal diet containing .44% total phosphorus and 1.24% calcium.…”