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Relative bioavailability of phosphorus in low-phytate soybean meal for broiler chicks. Researchers at Purdue University conducted a fourteen-day
chick bioassay to estimate the relative bioavailability of phosphorus
in a low-phytate soybean meal. A corn-soybean meal basal diet was formulated
to supply 3.3 g/kg total phosphorus and 10.5 g/kg calcium. Three reference
diets were also formulated by the addition of 0, 0.5, or 1.0 g/kg total
phosphorus from monosodium phosphate. Four test diets were formulated
with the addition of 0.5 or 1.0 g/kg total phosphorus from either the
low-phytate soybean meal or a normal soybean meal. Each diet was fed
to six replicated cages of four birds. The birds were fed for two weeks
and the experiment was terminated when the birds were three weeks old.
Body weight gain (P<0.01) and feed intake (P<0.05) increased linearly
as supplement dietary phosphorus was increased for the chicks fed diets
containing the monosodium phosphate or the low-phytate soybean meal.
Tibia mineral content and tibia ash weight increased linearly (P<0.001)
with increased levels of phosphorus from the monosodium phosphate, low-phytate
soybean meal or regular soybean meal treatments. The relative bioavailability
of phosphorus for the low-phytate soybean meal and the regular soybean
meal using the tibia ash weight method was estimated at 52+/-10% and
36+/-8%, respectively. Whereas, using the tibia mineral content method,
the values were 61+/-9% and 39+/-7% for the low-phytate soybean meal
and regular soybean meal. These results indicate that phosphorus in
the low-phytate soybean meal was 44-56% more available compared to the
regular soybean meal. (The development of low-phytate soybean varieties
that could be processed into low-phytate soybean meal would greatly
improve the bioavailabilty of the phosphorus in soybean meal. Using
these value-added soybean meals would allow the nutritionist to formulate
poultry (and swine) rations using less supplemental phosphorus ingredients).
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