Review: Phosphorus in Fish Nutrition

The particle size
Cromwell (1989) suggested that variable availability of P in meat and bone meal among investigators is at least
partly due to differences in the bone particle size, and that large bone particles are poorly available to pigs. The
author also stated that the availability of P in defluorinated rock phosphate is related to the particle size, with finer
particles being slightly more available than coarse particles in pigs. Eya & Lovell (1997) reported that finely
ground defluorinated rock phosphate was more available to channel cat fish than the coasely ground material (82%
vs 55%). Vielma et al. (1999) reported that P in finely ground bone was more available for rainbow trout (initial
wt 3 g) than P in coarsely ground bone based on whole-body ash, P and Ca concentrations.
Measuring the availability of various P compounds
VonGohren (1861) found that supplementing hay with Ca-Mg-phosphate greatly increas ed the retention of these
minerals by the lamb. Soxhlet (1878) determined the retention percentages of ash, P, Ca, Mg, Fe, K, Na and Cl in
milk by young calves. The data showed that 72.5% of P and 97% of Ca in the milk were retained. Tereg &
Arnold (1883) measured the contents of P, Ca, and N in food, urine and feces of the dog fed diets supplemented
with either Ca-carbonate, primary, secondary or tertiary phosphates, and estimated P retention based on the balance.
Kohler et al. (1904) determined the retention of various P compounds in yearling lambs as follows: 13.1% for
precipitated bone earth, 14.2% for calcined bones, 26% for dicalcic P, and 35.5% for tricalcic P. With a younger
lamb, these P compounds were better ret ained. Higgins & Sheard (1933) found no differences in the assimilation
of secondary and tertiary phosphates by the chick. Rottensten & Maynard (1934) compared the assimilation of P
from dicalcium phosphate, tricalcium phosphate, bone calcium phosphate, and cooked bone meal, and found no
significant di fferences among these sources. Gillis et al. (1948) determined P availability of various P sources in
chicks.
Uncommon P sources
Paquelin & Joly (1877, 1878) administered 2 g of sodium pyrophosphate, Na 4P 2O 7, daily for 5 days or total 5 g of
sodium hypophosphite, NaH 2PO 2, in 5 days to a woman, and found that both were apparently all eliminated in the
urine unchanged. Panzer (1902) wrote, "Ca hypophosphites fed to a dog is quickly and almost completely
absorbed, passes through the organism without being held back anywhere, and is completely eliminated within 24
h." Heffter (1903) report ed, “in healthy organism phosphorus acid (H 3PO 3) is completely oxidized,
metaphosphates, Na 3P 3O 9, are changed to the ortho-form, while pyrophosphates and hypophosphites are excreted
unchanged.” Shelling (1932) studied the utilization of pyrophosphate, metaphosphate, and hypophosphite in
parathyroidectomized rats, and reported that pyrophosphate was utilized while the latter two types were inert.
Gillis et al. (1954) determined the relative bioavailability of 38 P compounds in chicks based on the slope ratio assay
of bone ash with tricalcium phosphate as a standard. They reported that orthophosphates including bones, feed
grade phosphates and defluorinated phosphates were more available (80% min) than pyrophosphates and
metaphosphates. Agricultural grade phosphates (super phosphate, triple super phosphate, monoammonium
phosphate) had comparable bioavailability to corresponding feed grade phosphates. Cromwell (1989) wrote that
the availability of P in Curacao phosphate, soft phosphate, colloidal clay, and high-fluorine rock phosphate was quite
low. Fernandes et al. (1999) fed chicks with a corn-soybean based diet supplemented with a test phosphate or
purified dicalcium phosphate (standard), and determined the relative bioavailability by the slope ratio procedure
based on weight gain, bone ash and bone strength. They noted that thermomagnesium appeared to be toxic, and
that agricultural-grade phosphates contained fluoride in the amounts higher than feed-grade phosphates (0.4-1.1% vs
0.03-0.2%), but the P in both sources was highly available. The authors suggested possible fluorine toxicity by
feeding agricultural grade phosphate for an ext ended period.
Measuring mineral absorption at various sections of the GI tract using an indigestible indicator
Wildt (1874, 1879) conducted digestion experiments on sheep. He analyzed the contents of different parts of the
alimentary tract for P, Ca, Mg, Na, K and Cl, and estimated their absorption during their passage through the
alimentary tract. He used silica as an inert dietary indicator to trace their absorption. The data showed
considerabl e secretion of (endogenous) minerals in certain parts of the digestive tract. This observation convinced
© 2000, 2005. Shozo H. Sugiura. All rights reserved.
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