Animal Husbandry Mimeograph June, 1957
Series No. 57-6
UTILIZATION OF PHOSPHORUS FROM DIFFERENT SOURCES BY RATS
L. R. Arrington, D. C. Bowen and D. C. Tomlin1
A number of phosphatic materials are available and produced
in Florida which can be used as supplements in livestock and poul-
try rations. An important measure of the value of these materials
as phosphorus sources is the utilization by animals. Barrentine,
Maynard and Loosli (1) and Ellis et al (3) have studied the utili-
zation of certain inorganic phosphorus supplements by rats and
found that inorganic sources were useful, but that there were dif-
ferences in utilization. These results were based in part upon
growth and bone ash of the rats. Similar experiments have been
conducted with poultry and swine using these criteria as a meas-
ure of utilization (2, 4, 5, 6, 7).
This experiment was designed to study the comparative utili-
zation, by rats, of three inorganic phosphates, two of which were
produced in Florida.
Defluorinated rock phosphate, soft phosphate with colloidal\
clay and reagent grade dicalcium phosphate (CaHP04) were used
separately to supply approximately two-thirds of the phosphorus
requirement. Defluorinated phosphate and soft phosphate were test
substances, and the calcium phosphate was used as the reference
standard. These were added to a semi-purified diet made of corn
1Arrington, Assistant Animal Nutritionist; Bowen, Student
Assistant; Tomlin, Research Assistant, Department of Animal Hus-
bandry and Nutrition.
meal 30 parts, casein 10, albumen 5, sucrose 20, starch 20,
vegetable oil 6, alphacel 5, Brewers yeast 1, vitamin mix 1 and
NaC1 1. The basal diet contained 0.13 percent phosphorus. Using
this basal diet, additional dietary treatments were prepared by
adding the supplements in amounts which provided 0.20 percent
phosphorus making a total of 0.33 percent phosphorus in each of
the experimental diets. Thus, more than half of the phosphorus
intake was supplied by the supplements. The phosphorus require-
ment for the rat is approximately 0.4 percent, but the intake from
the experimental diets was kept low so that maximum utilization
would be possible. Calcium carbonate was added to adjust the cal-
cium to phosphorus ratio at 1.8 to 1.
Forty-eight weanling rats of the Long-Evans strain, 22-24
days of age were used as experimental animals. They were divided
into four groups of seven males and five females each. Animals
were housed in metal cages with raised screen bottoms in a room
with the temperature controlled at 780 F. Experimental diets and
fresh water were supplied ad libitum and the total feed consumed
by each group was measured. After six weeks on the experiment
(nine weeks of age), the rats were sacrificed and both femur
bones removed for use in bone ash determinations. Bones were
freed of adhering tissue, dried for 24 hours at 1050 C then ashed
in a muffle furnace for 24 hours at 6000 C. The rats were sacri-
ficed after six weeks on experiment so that bone ash determinations
would represent rats in an actively growing state.
Growth data in terms of weight gain at three and six weeks,
feed efficiency, total bone ash and femur size are recorded in
Table I. Rats which were fed the basal diet without any supple-
mentation gained less and accumulated less total ash in the bones
than did those which were supplemented. Each of the phosphorus
supplements promoted greater gains and increased bone ash demon-
strating the utilization of phosphorus from these sources.
Weight Gain, Feed Efficiency, Bone Ash and Femur
Size of Rats Fed Phosphorus from Different Sources
Source Av. live wt. Grams feed/ Bone ash Femur size
Gains (grams) Gram gain (%) (% body wt.)
3 wks 6 wks
Basal 43 107 4.7 48.3 .279
Phosphate 72 168 3.1 56.4 .301
Defluorinated 76 175 3.2 58.5 .310
CaHP04 84 185 3.0 60.0 .319
Although each of the supplements was utilized, there were
differences in availability or utilization which were reflected
in growth and bone ash values. Phosphorus in CaHPO4 was most avail-
able followed by defluorinated phosphate and soft phosphate. If
the value for CaHPO4 is arbitrarily placed at 100, then the rela-
tive value for defluorinated phosphate would be 94 percent as
available based on weight gain and 97 on bone ash. Using the same
comparison, the values for soft phosphate would be 91 and 94.
Using these criteria of measurement with rats, the avail-
ability of phosphorus in soft phosphate was greater than has
been indicated for chicks. It may be that there is a species
difference and that phosphorus in soft phosphate is relatively
more available to rats. It may be that the minimum phosphorus
requirement for the growing rat is much less than that supplied
and that the supplemental phosphates were not called upon or not
needed in full to supply needed phosphorus. On the other hand,
those rats on the basal diet which was not supplemented made poor
gains and had much less bone ash than those which were supple-
mented. This demonstrates that additional phosphorus was needed
and that it was available from each of the phosphate supplements.
1. Barrentine, B. F., L. A. Maynard and J. K. Loosli. 1944.
The availability of the calcium and phosphorus of defluori-
nated rock phosphate for the rat. J. Nutrition 27: 35.
2. Chapman, H. L., Jr., J. Kastelic, G. C. Ashton and D. V.
Catron. 1955. A comparison of phosphorus from different
sources for growing and finishing swine. J. Animal Sci.
3. Ellis, N. R., C. A. Cabell, W. P. Elmslie, G. S. Fraps,
P. H. Phillips and Dorothy E. Williams. 1945. Nutritive
evaluation of defluorinated phosphates and other phosphorus
supplements. III. Utilization experiments with rats. J.
Assoc. Official Agr. Chem. 28: 129.
4. Gillis, M. B., L. C. Norris and G. F. Heuser. 1954. Studies
on the Biological value of inorganic phosphates. J. Nutrition
5. Gobble, J. L., R. C. Miller, G. W. Sherritt and H. W. Dunne.
1956. Soft phosphate with colloidal clay as a source of
phosphorus for growing and fattening pigs. Pa. Agr. Expt.
Sta. Bull. 609.
6. Grau, C. R. and Phyllis A. Zweigart. 1953. Phosphatic clay
as a phosphorus source for chicks. Poultry Sci. 32: 500.
7. Wilcox, R. A., C. W. Carlson, W. Kohlmeyer and G. F. Gastler.
1954. The availability of phosphorus from different sources
for poults fed purified diets. Poultry Sci. 33: 1910