Maataloustieteellinen A ikakauskirja
Vol. 62: 435—443, 1990

Microbial phytase supplementation for improving availability of
plant phosphorus in the diet of the growing pigs

MATTI NÄSI

Department of Animal Husbandry,
University of Helsinki, 00710 Helsinki, Finland

Abstract. The effect of a phytase supplement produced by Aspergillus niger on phytin-
phosphorus availability for pigs on phytase deficient maize-soybean meal diets was measured
in two digestibility and balance experiments involving twelve growing pigs. Apparent digesti-
bility of P in diets without inorganic-P supplementation or with low addition (0.18 of total
P) was significantly lower than in the control diets (0.16 and 0.23 vs. 0.42; P<0.01), respec-
tively. Phytase supplementation improved P digestibility (P<0.01) such that plant-P digesti-
bility (0.40 and 0.28) rose to the same level as the control diet. P retention was also increased
significantly by phytase supplementation. Calcium digestibility and retention were higher in
phytase treated diets. Due to its effect on phytate-P availability, phytase treatment of feed-
stuffs allows a greater proportion on the pig’s P requirement to be met by P of plant origin.

Index words: phytase, phosphorus, minerals, digestibility, availability, pig.

Introduction

In cereals and vegetable protein sources half
to three quarters of the phosphorus (P) occurs
organically bound with phytic acid in form of
myoinositolphosphate, which is the major
storage form of P in plant tissue. The availa-
bility of plant-phytate-P is lower for pigs than
that of non-phytate-P in plants or inorganic
P of mineral sources and is variable among
different plant feeds as reviewed by Crom-
well (1980, 1989) and Jongbloed (1987). In
order for the pigs to utilize the phosphorus
from phytate it must be hydrolysed by phy-
tate-degrading enzymes to yield phosphates.

Moreover, phytic acid binds strongly to other
essential dietary minerals, such as calcium,
zinc, magnesium, iron and copper, reducing
their availability in the digestive tract of
monogastrics (Zhu et al. 1990).

Although, phytase activity occurs in mi-
crobes and microbial phytases can be pro-
duced biotechnically, there are no reports
of improved plant P utilization by pigs re-
ceiving phytase supplements (Shurson et al.
1983 Jongbloed 1987). However, in broilers
phytase supplementation of diets (Kiiskinen
and Piironen 1990) and in chicks the addi-

435

JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND

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tion of phytase producing organisms to the
diet has resulted in a marked improvement in
the utilization of phytate-P (Nelson et al.
1971). In pigs, similar attempts to supplement
the diets with a dried yeast product have been
unsuccessful (Cromwell et al. 1978).

The objective of this study was to evaluate
the possibility of improving the usage of phos-
phorus from plant ingredients by a phytase
supplement produced by Aspergillus niger
with a new technology. A maize-soybean meal
pig ration containing low naturally occurring
phytase activity was chosen as the test diet.
Attention was also paid to the reduction of
the phosphorus content of pig excrement in
order to avoid the accumulation of phosphates
in soils.

Materials and methods

Two experiments were conducted with six
castrated growing pigs, in which the effect of

added microbial phytase on the availability of
plant phosphorus (P) was measured using bal-
ance assay.

The experimental diets were composed of
maize (880 g/kg) and soybean meal (120 g/kg)
and the daily allowances were 2500—2700 g.
The control diets in both exps. were sup-
plemented with dicalcium phosphate to give
6.5 g/kg total phosphorus in the ration. In
exp. 1, diets 2 and 3 were supplemented with
3.3 g/kg of dicalcium phosphate to provide
0.50 of total P of the control diet mixture. In
exp. 2 no inorganic P-supplementation was
added to diets 2 and 3 (Table 2). In control
diets, maize and soybean meal contributed
0.44 of the total supply of P and dicalcium
phosphate provided 0.56. Calcium was added
in all of the rations to provide diets with a con-
tent of 0.80 % total calcium. The trace ele-
ments and vitamins were supplemented ac-
cording to Finnish recommendations (Salo et
ai. 1982) in all treatments.

Table 1. Chemical composition of the experimental feed ingredients (g/kg DM).

Dry Ash Crude Ether Crude Phos- Phytic
matter protein extract carbo- phorus acid

hydrates

Soybean meal
Exp. 1 868 65 502 36 398 7.87 4.33
Exp. 2 895 66 497 36 401 7.29 4.38

Maize
Exp. 1 860 13 98 50 839 2.80 2.82
Exp. 2 878 15 95 58 832 2.78 3.04

Dicalcium
phosphate

Exp. 1 802 782 185.44
Exp. 2 983 853 166.27

Table 2. Feed intake of pigs. (Exp. 1, Exp. 2), (g DM/d),

Experiment I II

Treatment 12 3 12 3

Maize 1950 1954 1955 1994 1921 1998
Soybean meal 269 269 269 277 267 278
Calcium carbonate 9 41 41 13 47 49
Dicalcium phosphate 52 9 9 57
Sodium chloride 5 5 5 5 5 5
Trace element prem. 15 15 15 16 16 16
Phytase supplement 11 2.3

436



The phytase product Finase-F (produced by
Alko Ltd., Rajamäki, Finland) was used in
both experiments. The level of supplementa-
tion in diet 3 in Exp. 1 was 100000 Pu/kg feed
(1 Pu is the amount of enzyme that liberates

1 nmol of inorganic phosphorus from sodium-
phytate in one minute, 37°C, pH 5.0) and
500 000 Pu/kg in Exp. 2, respectively. The en-
zyme was added to the ration in liquid form
just before feeding. Finase-F preparation is
produced by Aspergillus niger var. and the
phytase is acid and heatresistant over broad
pH and temperature ranges (pH 2.0—6.0 and
up to 60°C).

The experiment had a 3 x 3 replicated Lat-
in square designs and the pigs had an average
liveweight of 78 and 98 kg in exp. 1 and 2,
respectively. Each period was comprised of 6
days of adjustment and 6 days of faeces and
urine total collection. The chemical analyses
of feeds and faeces were performed accord-
ing to the official procedures. Phytic acid con-
tents were analysed using the method of Ca-
mire and Clydesdale (1982). Phosphorus
was determined after dry ashing by the meth-
od of Tayssky and Shorr (1953) and miner-
als were measured on the diet ingredients, fae-
ces and urine with a Varian Techtron AAIOOO
atomic-absorption spectrophotometer.

Results and discussion

Average daily dry matter intake of thepigs
was 79 g in Exp. 1 and 75 g in Exp. 2 per kg
W 0 75. Daily phosphorus intakes of pigs
receiving the control diet were 17.2 g. Pigs on
diets 2 and 3 in Exp. 1 consumed 9.3 gP/day,
and in Exp. 2 consumed 7.5 g/day (Table 2).
Dicalcium phosphate contributed 0.56 of the
total P supply in control diets and 0.18 of to-
tal Pin diets 2 and 3of Exp. 1. No supplemen-
tal phosphorus was added in Exp. 2 on diets
2 and 3; all of the P supply was of plant origin.

Organic matter digestibility was not differ-
ent between the treatments in either experi-
ment (P>0.05, Table 3). Finase-F also con-
tains some proteinase, amylase and pectinase
activity, however, digestibility was not af-
fected in this trial. The ash digestibility was
improved significantly by phytase supplemen-
tation (PcO.Ol) in Exp. 2. and showed a simi-
lar tendency in Exp. 1. Nitrogen digestibility
was significantly higher in Exp. 2. in pigs
receiving diets without an inorganic phospho-
rus supplement (P < 0.05). However, there was
no effect on N balance (Table 4). A number
of other investigations have pointed out that
there is often strong binding between phytic
acid and protein (Zhu 1990) but in this study

Table 3. Digestibilities of the nutrients in pigs on the experimental diets.

Org. Crude Ether Crude Ash
matter prot. extr. carbo-

hydr.

Experiment 1.
Diet 1 0.911 0.866 0.734 0.929 0.486
Diet 2 0.905 0.856 0.721 0.924 0.525
Diet 3 0.907 0.859 0.726 0.926 0.548
SEM 0.0036 0.0046 0.0071 0.0037 0.0239
Statist, signif. NS NS NS NS NS

Experiment 2.
Diet 1 0.903 0.851» 0.809 0.916 0.524»
Diet 2 0.919 0.884b 0.833 0.931 0.560»
Diet 3 0.914 0.873»" 0.817 0.928 0.642"
SEM 0.0043 0.0065 0.0082 0.0038 0.017
Statist, signif. NS * NS NS ••

»-">: * P<0.05, •* P<o.ol

437



Table 4. Nitrogen balance and protein utilization.

Exp. 1.

Treatment 1 2 3 SEM Statist.
signif.

N intake, g/d 52.31" 52.43» 52.83" 0.110 *

N excretion in faeces 7.00 7.53 7.47 0.236 NS
N absorption, g/d 45.31 44.90 45.35 0.312 NS
N digestibility 0.866 0.856 0.859 0.0046 NS
N excretion in urine 22.32 23.73 23.28 0.474 NS
N retained, g/d 22.99 21.17 22.07 0.461 NS

of intake 0.440" 0.404" 0.419b 0.0084 •

of absorption 0.508 0.472 0.487 0.0097 NS
g/kg W°" 0.790 0.731 0.770 0.015 NS

Biological value 0.601 0.567 0.581 0.0091 NS

Exp. 2.

Treatment 1 2 3 SEM Statist.
signif.

N intake, g/d 52.29 51.62 52.39 0.433 NS
N excretion in faeces 7.76" 5.98b 6.66"b 0.350 *

N absorption, g/d 44.53 45.63 45.73 0.323 NS
N digestibility 0.851» 0.884" 0.873»" 0.0065 *

N excretion in urine 22.13 23.65 22.96 0.774 NS
N retained, g/d 22.40 21.98 22.77 0.673 NS

of intake 0.428 0.428 0.435 0.0161 NS
of absorption 0.504 0.483 0.498 0.0151 NS
g/kg W°-75 0.72 0.71 0.73 0.023 NS

Biological value 0.603 0.581 0.596 0.0140 NS

_». » p<0.05.

phytase treatment did not result any improve-
ment in protein digestibility.

The apparent digestibility of P on the con-
trol diet averaged 0.42 in both trials and was
significantly higher (P<0.05, 0.01) than that
of the diets without inorganic phosphorus sup-
plementation (Exp. 2) or with low (0.18 con-
tribution of total P) phosphate addition in
Exp. 1 (Table 5). Phytase supplementation of
the diet resulted a significant improvement in
phosphorus digestibility (PcO.Ol) compared
with that of the unsupplemented diet. Phytase
improved plant-P digestibility such that it rose
to the same level as the inorganic-P sup-
plemented diet (Exp. 2). Also in Exp. 1 phy-
tase enhanced apparent digestibility of P by
five percentage units (P>0.05). The apparent
digestibility assay of the P in the total diet,
however, poses some difficulties in the in-
terpretation of the results, particularly when
P supplies are different as in present study.

Endogenous P secretions also complicate the
measurement (Jongbloed 1987), who re-
ported the valueof 5 mg/kg metabolic weight
excreted in faeces. An approximation of these
daily P-losses in pig is 1.5—2.5 g/100 kg body
weight (Arc 1981).

Similar low apparent P digestibilities as in
present maize-soybean meal diets have been
reported in cereals or cereal-based diets con-
taining no supplemental P (Pierce et al.
1977, Calvert et al. 1978, Jongbloed 1987,
Oksbjerg 1988). Phosphorus from phytate
cannot be absorbed in its original form by pigs
and so it must first be released by hydrolysis
by phytate-degrading enzymes to yield inositol
and phosphoric acid. Almost all vegetable
feed ingredients poses phytase, although with
different levels of activity (Nelson 1969).
Maize has been reported to have very low con-
tents of natural phytase (Calvert et al. 1978,
Pointillart et al. 1984, 1988, Oksbjerk

438



Table 5. Phosphorus excretion, apparent absorption and retention in pigs.

Exp. 1.

Treatment 1 2 3 SEM Statist.
signif.

P intake, g/d 17.16» 9.30" 9.34" 0.107 ***

P excretion in faeces 9.69» 7.12 b 6.71" 0.197 ***

P absorption, g/d 7.47» 2.18" 2.63b 0.207 *»*

P digestibility 0.43» 0.235" 0.284»" 0.0216 ***

P excretion in urine 5.59" 0.38 b 0.20b 0.317 **

P retained, g/d 2.23 1.79 2.43 0.380 NS
of intake 0.128 0.193 0.261 0.0312 NS
of absorption 0.312= 0.828»" 0.927"" 0.0315 **

g/kg W°" 0.07» 0.06» 0.09» 0.063 NS

Exp. 2.

Treatment 1 2 3 SEM Statist.
signif.

P intake, g/d 17.19» 7.54" 7.65" 0.103 ***

P excretion in faeces 10.07» 6.33" 4.59s 0.293 •*

P absorption, g/d 7.11» 1.21" 3.06' 0.276 *•*

P digestibility 0.414» 0.162" 0.400» 0.0271 ***

P excretion in urine 3.37" 0.16" 0.06" 0.094 ***

P retained, g/d 3.72" 1.04" 3.00» 0.212 •••

of intake 0.217» 0.139» 0.392" 0.0206 ***

of absorption 0.523» 0.887" 0.979" 0.0283 ***

g/kg W°" 0.12» 0.03" 0.10» 0.007 ***

a_c; * pc0.05, *• P<o.ool, P<o.ool

1988), which is why this diet was chosen to
test microbial phytase supplementation even
though maize is not used in pig feeding in Fin-
land. In contrast to this the seed coats of
wheat and barley have relatively high phytase
activity. The optimum pH for plant phytase
is about 4.0—6.0 as reviewed by Irwing

(1980) therefore plant phytase probably does
not survive the acid conditions of the stomach.

P digestibility in maize-based diets has been
improved by treatments other than microbial
phytase supplementation. Frape et al. (1979)
and Baoheri and Gueouen (1985) have
shown that absorption coefficients of phos-
phorus in a maize SBM diet without added P
were increased from 0.36 to 0.48 by introduc-
tion of 200 g/kg wheat bran into the diet.
Similarly, Fourdin et al. (1988) reported that
rye bran supplementation (200 g/kg) im-
proved P retention 40—50 % in pigs on low
P maize diets. In high-moisture maize the P

is 3 to 4 times more available than in dried
grain (Boyd et al. 1983). The improvements
with those treatments have been similar or bet-
ter than that of the present study of micro-
bial phytase supplementation.

Besides being present in the feedstuffs, phy-
tases are produced by the microbes in the in-
testine and are also secreted by the intestinal
tract of the pig. Intestinal alkaline phospha-
tase can hydrolyse some phytate (Pointil-
lako et ai. 1984). However, it has been con-
cluded that intestinal phytase does not seem
to be of great significance for the hydrolysis
of phytate (Pointillart et al. 1984). In the
large intestine with its rich microbial flora
phytate can be hydrolysed by bacterial phy-
tases. However, the pig’s absorption of phos-
phorus in the large intestine is very limited and
no P or only a limited amount of P was ab-
sorbed beyond an ileal fistula (Jorgensen et
al. 1985).

439



The retention of phosphorus was 0.13—

0.22 of P intake on the control diets and
0.14—0.19 on diets without inorganic P sup-
plementation. This low availability is in ac-
cordance with existing literature. Microbial
phytase supplementation improved retention
of phosphorus to the level of 0.26—0.39 and
the differencewas significant (P<0.01) com-
pared with the untreated non P-supplemented
diet. Retention of the absorbed P was very
high (0.93—0.98) in diets supplemented with
phytase and was 0.10 higher relative to the un-
treated diets (P<0.05 in the first Exp.). Some
low-molecular weight myoinositol phosphates
were probably absorbed but could not be uti-
lized by the pig.

The retention of P in Exp. 1 was consider-
able lower compared to Exp. 2, but the rea-
son for this remains uncertain. Average daily
gain of pigs in Exp. 1 was 729 g, while it was
854 g in Exp. 2. The pigs on low-P phytase
unsupplemented diet had the lowest gains as
well as the lowest P-retention. The effect of
phytase supplementation was different be-
tween the two experiments due to the appli-
cation level, which was five-fold higher in the
second trial. Jongbloed (1987) found that in
slaughter pigs on average 4.9 g P/kg live
weight was retained. The phosphorus availa-
bility in most inorganic phosphate supple-
ments approaches 0.7 to 1.0 (Cromwell
1989, Jongbloed 1987, Den Hartog et al.
1988).

Calcium digestibility was improved by the
phytase supplementation and retained Ca was
significantly (P<0.01) higher compared to the
untreated diet (Table 6). When the intake of
Ca is adequate but that of P inadequate, the
retention of Ca falls (Jongbloed 1987). In the
present study the calculated Ca/P ratios were
0.93 and 2.07 for control and experimental
groups, respectively, while the optimum Ca/P
ratio is from 1.2 to 1.3:1 (Arc 1981). Digest-
ibility of magnesium also tended to be in-
creased by the phytase treatment but retention
was not affected. Iron supply was higher in
the control diet due to the high content of iron
in dicalciumphosphate. Fe digestibility was

not different between diets but retention in the
control diet was significantly higher. Copper
and zinc digestibility and retention were higher
in diets without phosphate addition but phy-
tase supplementation did not affect any differ-
ence in utilization. Phytic acid readily forms
complexes with several essential minerals such
as calcium, iron, zinc and manganese and also
protein impairing their utilization by the ani-
mal (Nelson et al. 1971).

There are no previous reports of successful
addition of microbial phytase to pig diets.
However, many of the fungi, bacteria and
yeasts are good sources of phytase. Attempts
to improve phytate utilization in pigs by in-
cluding a dried yeast product in the diet have
been unsuccessful (Cromwell et al. 1978). In
contrast, several studies with chicks have
demonstrated that the addition of phytase-
producing organisms to the diet can result in
a marked improvement in the utilization of
phytate phosphorus (Nelson et al. 1971,
Cromwell 1980). Shurson et al. (1983) was
not able to improve phytate utilization in pigs
by including a yeast phytase in the diet. It is
possible that the additions of phytase have
been insufficient or that the phytase used
has not been resistant to the low pH in the
stomach of the pig. In this study 100 000
Pu/kg was not sufficient because increasing
phytase activity gave a greater response in the
Exp. 2. The Finase-F preparation is ther-
motolerant and acid-resistant to a pH value
of 2. Successful treatments in poultry have
been also reported. Nelson et al. (1971)
added phytase produced by a culture of
Aspergillus ficium to the diet of chickens and
found an increase in bone ash content com-
pared to control. Kiiskinen and Piironen
(1990) showed improved plant-P digestibility
in broilers after phytase supplementation.

In conclusion, the results of present study
demonstrate that addition of a microbial phy-
tate degrading enzyme in maize-soybean meal
diet enhances the absorption of vegetable
phosphorus and other essential minerals.
More of the pigs’ requirement for phospho-
rus could be met by P in maize and SBM if

440



Table 6. Mineral excretion, apparent absorption and retention in pigs.

Exp. 2.

Treatments 1 2 3 SEM Statis.
signif.

Calcium
Intake, g/d 15.91 15.60 15.84 0.131 NS
Excret. in faeces, g/d 9.72" 8.62»" 7.64" 0.419 *

Absorption 0.388" 0.450»" 0.517" 0.0248 *

Excretion in urine, g/d 0.52» 3.65» 1.87c 0.186 ***

Retention, g/d 5.67* 3.33" 6.33» 0.426 **

of intake 0.356» 0.216" 0.400» 0.0287 **

of absorption 0.922» 0.466" 0.775c 0.0328 **»

Magnesium
Intake, g/d 3.48 3.47 3.52 0.029 NS
Excret. in faeces, g/d 2.53» 2.17»" 2.07" 0.089 *

Absorption 0.273» 0.375" 0.412" 0.0243 ••

Excretion in urine, g/d 0.42» 0.74" 0.77" 0.032 ***

Retention, g/d 0.54 0.56 0.68 0.096 NS
of intake 0.153 0.163 0.193 0.0282 NS
of absorption 0.544 0.421 0.463 0.0481 NS

Iron
Intake, mg/d 561» 338" 344" 3.4 ***

Excret. in faeces, mg/d 408» 279" 280" 11.5 ***

Absorption 0.272 0.177 0.184 0.0279 NS
Excretion in urine, mg/d 3.10» 1.42" 1.62" 0.301 ••

Retention, mg/d 150" 58" 62" 11.2 ***

of intake 0.266 0.173 0.179 0.0276 NS
of absorption 0.977 0.972 0.974 0.0038 NS

Copper
Intake, mg/d 184 182 184 1.5 NS
Excret. in faeces, mg/d 178» 156" 157» 5.7 *

Absorption 0.031» 0.143»" 0.145" 0.0294 * •

Excretion in urine, mg/d 1.7 2.1 1.3 0.31 NS
Retention, mg/d 4.3» 23.4»" 25.6" 5.15 *

of intake 0.021» 0.136»" 0.138" 0.0291 *

of absorption 0.816 0.903 0.943 0.0183 NS
Zinc
Intake, mg/d 189 187 190 1.6 NS
Excret. in faeces, mg/d 184» 159" 155' 6.0 *

Absorption 0.019» 0.150" 0.181" 0.0314 *

Excretion in urine, mg/d 10.6 13.3 13.3 2.38 NS
Retention, mg/d -6.4» 14.4»" 21.2" 5.66 *

of intake -0.038» 0.078»" 0.111" 0.0314 *

of absorption 1.467» 0.416" 0.531" 0.2260 *

•->:
• P<0.05, *• P<o.ol, »»� P<o.ool.

phosphorus could be converted to an available
form. Phosphorus content in pig manure
could be reduced followed the improved plant-
P utilization with the present phytase treat-
ment of the feed. Accumulation of P in culti-
vated fields is increased by using manures with
high P content. Whether the use of enzymatic
treatment to release plant phosphorus is eco-
nomically feasible compared to addition of

other sources of phosphorus to feed remains
to be determined.

Acknowledgements. The author is grateful to Ms. Ulla
Roiha, M. Agr.Sc. and Mr. Juha Suomi for technical as-
sistance and to Ms, Hilkka Siljander-Rasi, M. Agr.Sc.
and Mr. Erkki Aimonen, M. Agr.Sc. for their valuable
assistance in statistical analysis. The financial support to
this study was received from Alko Ltd.

441



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SELOSTUS

Fytaasilisäyksen vaikutus kasviperäisen
fosforin hyväksikäyttöön
lihasian ruokinnassa

Matti Näsi
Helsingin yliopisto, kolieläinlieleen laitos

Kahdessa sulavuus- ja tasekokeessa tutkittiin biotek-
nisesti tuotetun sienifytaasin tehoa kasviperäisen fytiini-
fosforin hyväksikäytön parantamiseen lihasikojen ruo-
kinnassa. Maissi-soijarouhedieetin fosforin sulavuus oli
alhainen,00.10.23,6—0.23, ja se oli merkitsevästi alempi kuin
fosfaatilla täydennetyn dieetin P:n sulavuus (0.42). Fy-
taasilisäys paransi merkitsevästi kasviperäisen fosforin su-
lavuutta((0.40.28). Fosforin pidättyminen lisääntyi
myös merkitsevästi fytaasikäsittelyn ansiosta. Samoin kal-

siumin sulavuutta japidättymistä voitiin parantaa fytaa-
silisäyksen avulla. Rehujen fytiinifosforin hyväksikäyt-
töä voitiin parantaa huomattavasti fytaasilisäyksellä ja
samalla saada aikaan sonnan fosforipitoisuuden alene-
mista. Fosfaattien käyttöä voitaisiin ilmeisesti vähentää
sikojen ruokinnassa lisäämällä orgaanisen fosforin käyt-
tökelpoisuutta ja siten vähentää lannan mukana poistu-
van fosforin määrää.

443