Gl. Cromwell et al., EFFICACY OF PHYTASE IN IMPROVING THE BIOAVAILABILITY OF PHOSPHORUS INSOYBEAN-MEAL AND CORN-SOYBEAN MEAL DIETS FOR PIGS, Journal of animal science, 71(7), 1993, pp. 1831-1840
Four experiments involving 225 pigs were conducted to assess the effic
acy of a microbial phytase (FINASE(TM), Alko Ltd. Biotechnology, Rajam
aki, Finland) produced by Aspergillus niger in corn-soybean meal or de
xtrose-cornstarch-soybean meal-based diets. In two experiments with gr
owing finishing pigs, fortified corn-soybean meal diets were formulate
d to be adequate (.50%) or inadequate (.40 or .30%) in P during the gr
owing phase followed by adequate (.40%) or inadequate (.30%) P in the
finishing phase. Mono-dicalcium phosphate was the source of supplement
al P. Half the diets were supplemented with phytase (500 phytase units
/g). Rate and efficiency of gain and bone breaking strength were decre
ased when P-deficient diets were fed. Phytase supplementation of the l
ow-P diets restored growth rate and feed:gain to levels that approache
d those of pigs fed the adequate-P control diet. Bone strength was par
tially restored to that of the controls. In two additional experiments
, pigs were fed low-P basal diets in which all the dietary P came from
soybean meal or a corn-soybean meal blend. Both diets contained .05%
available P. Graded levels of monosodium phosphate were added to these
diets, up to .15% added P, to establish a standard curve. Phytase was
added to the basal diet at 250, 500, or 1,000 units/g. Growth rate an
d bone strength improved linearly (P < .01) with added monosodium phos
phate and with increasing levels of supplemental phytase. Based on est
imates of total and available P intakes, the highest level of phytase
(1,000 units/g) increased the bioavailability of the P from 25% in the
soybean meal diet to 57% in the phytase-supplemented diet, and from 1
5% in the corn-soybean diet to 43% in the phytase-supplemented diet. E
xpressed on the basis of the improvement in phytate P availability, th
is level of phytase converted approximately one-third of the unavailab
le P to an available form. The results indicate that the phytase was e
fficacious in improving the bioavailability of phytate P for pigs.