Gl. Cromwell et al., EFFICACY OF LOW-ACTIVITY, MICROBIAL PHYTASE IN IMPROVING THE BIOAVAILABILITY OF PHOSPHORUS IN CORN-SOYBEAN MEAL DIETS FOR PIGS, Journal of animal science, 73(2), 1995, pp. 449-456
Two experiments involving 115 pigs were conducted to assess the effica
cy of a microbial phytase (Allzyme Phytase(TM); Alltech, Nicholasville
, KY) produced by Aspergillus niger in low-P, corn-soybean meal-based
diets. The phytase supplement contained 50 phytase units/g and 1.43% P
. In Exp. 1, growing-finishing pigs were fed fortified corn-soybean me
al diets formulated to be adequate (.50%) or inadequate (.30%) in P du
ring the growing phase (38 to 57 kg BW) followed by adequate (.40%) or
inadequate (.30%) P, respectively, during the finishing phase (to 101
kg BW). Dicalcium phosphate was the source of supplemental P. Half th
e diets were supplemented with phytase at 500 phytase units/kg. Rate a
nd efficiency of gain and bone breaking strength were decreased (P < .
01) when the low-P diet was fed. Adding phytase to the low-P diet rest
ored performance and bone breaking strength (P < .01) to levels that a
pproached those of pigs fed the adequate-P diet. In Exp. 2, growing pi
gs (13 kg BW), were fed a low-P (.32% total P; .048% available P) basa
l diet supplemented with graded levels of monosodium phosphate to prov
ide 0, .075, and .15% added P or with phytase to supply 250, 500, 1,00
0, or 2,000 phytase units/kg. Chromic oxide was included as an indiges
tible marker for determining apparent absorption and fecal excretion o
f P. Performance and bone strength increased linearly with added monos
odium phosphate (P < .01) and with increasing levels of supplemental p
hytase (P < .05). A portion of these increases from phytase was attrib
uted to the P supplied by the phytase mix (.007, .014, .028, .057%, re
spectively). Based on bone strength and total and available P intakes,
the four levels of phytase increased the bioavailability of the P in
the corn-soybean meal mixture by 4, 5, 8, and 15 percentage units, res
pectively. Approximately 4, 7, 10, and 15% of the unavailable P was ma
de available by the four levels of phytase, respectively. Phytase incr
eased (P < .01) the apparent absorption of the corn-soybean meal P. Ph
ytase did not affect the daily excretion of P, but it reduced (P < .01
) the percentage of dietary P that was excreted in the feces. These re
sults indicate that this source of phytase was moderately efficacious
in improving the bioavailability of phytate P for pigs.