A .W. Jongbloed et al. Livestock Production Science 67 2000 113 –122
119 Table 6
21 21
Average pH, osmolarity mosmol l , Ca, Mg and P content g l
in the urine as affected by microbial phytase, organic acids and their interaction
Phytase Acid
pH Osm.
Ca Mg
P
ab ab
2 –
8.01 535
1.12 0.23
0.0073
a ab
2 Lactic
7.96 659
1.42 0.26
0.0069
b a
2 Formic
7.95 572
1.03 0.21
0.0058
c b
1 –
7.81 577
0.54 0.20
0.0166
c ab
1 Lactic
7.87 655
0.38 0.23
0.0142
c ab
1 Formic
7.88 622
0.44 0.23
0.0109 RMSE
0.17 109
0.321 0.045
0.0100 P values
Phytase 0.105
0.472 ,0.001
0.545 0.018
Acids 0.999
0.152 0.452
0.452 0.654
Phytase3acids 0.755
0.810 0.173
0.173 0.851
abcd
Within a column, values with different superscripts are significantly different at P ,0.05. RMSE, root mean square error; ]
Œ
S.E.M.5RMSE n, where n 58 for no acid means and n 56 for acid means.
formance of the pigs is therefore predominantly due 3.4. Characteristics of urine
to the higher feed intake, although also positive effects have been noted by microbial phytase even
The urinary pH, osmolarity and Mg content were when the pigs are fed above their P requirement
similar, irrespective
of supplementary
acid or
Jongbloed et al., 1996. phytase doses Table 6. No effect of these organic
Also, the supplementary organic acids had a acids on urinary pH was expected because these
positive effect on performance of the pigs in the diets acids are known to be metabolised in the liver for
with and without microbial phytase. This enhanced various metabolic processes. The concentration of Ca
response is reported in numerous publications as in the urine was reduced by microbial phytase P ,
reviewed by Partanen and Mroz 1999, although the 0.001 because the deficit of digestible P in the
effect in our experiment is confounded with a higher metabolic pool was much lower Jongbloed, 1987;
supply of digestible P on average 0.2 g kg. Also, Mroz et al., 1993. Microbial phytase increased
Radcliffe et al. 1998 reported a better performance significantly the P concentration in the urine. How-
of pigs fed diets with 1.5 to 3.0 citric acid at ever, concentrations are very low, which means that
digestible P levels below requirement. It is generally the animals on all treatments were still fed below
assumed that the response of pigs to organic acids their P requirement.
declines with increasing age of the animal and development of gastric secretion Kirchgessner and
Roth, 1980, 1982; Easter, 1988, but for the category
4. Discussion
of pigs we used, the positive effect of organic acids on performance is still quantitatively important.
4.1. Effect on performance 4.2. Apparent total tract digestibility of DM and
The addition of microbial phytase in this experi- OM
ment resulted in an increase from 1.0 to 1.7 g of
21
digestible P kg diet, and had a substantial positive
Digestibility of DM was significantly enhanced by effect on feed intake, daily gain and feed conversion
microbial phytase
10.30-units and
acid ratio. This has been documented for all experiments
10.86-units, but no interactions could be demon- with supplementary microbial phytase to diets with a
strated. Jongbloed et al. 1996 surveyed data from supply of digestible P below the requirement of the
18 experiments they performed at their experimental pig Jongbloed et al., 1994. The improved per-
120 A
.W. Jongbloed et al. Livestock Production Science 67 2000 113 –122
station and found that microbial phytase enhanced generated digestible Ca to generated digestible P in
the digestibility of DM by 0.5460.81-units. This diets with constant Ca content, Jongbloed et al.
was significantly different from zero. The positive 1996 concluded from 12 experiments performed at
effect on DM digestibility is to a large extent their own experimental station that this ratio was
attributed to phytase’s positive effect on ash di- 0.5560.19. In the current experiment this ratio was
gestibility, because no effect of microbial phytase on 0.39 0.6950.56, which is equal to a mean value
OM digestibility could be demonstrated. This is in found from those experiments. However, the mean
line with the literature data compiled by Jongbloed et ratio from data compiled by Jongbloed et al. 1996
al. 1996 from outside of his experimental station, outside of their own experimental station was higher,
where the effect of microbial phytase in nine experi- i.e. 0.8460.38. Maybe, the higher Ca concentrations
ments was 0.3360.72-units, which is not signifi- in these diets can explain the higher ratio Mroz et
cantly different from zero. In this study the organic al., 1993.
21
acids significantly enhanced the total tract digestibili- As expected, microbial phytase 410 FTU kg
ty of DM 10.86-units and OM 10.64-units increased the apparent digestibility of P 16.5-
21
significantly. Since maize starch estimated DM units which is equal to 0.69 g of digestible P kg
digestibility equals 100 was exchanged by these of diet. This value fits fairly well with the dose–
acids in the diets, the positive effect of the acids is response curve developed by Beers and Jongbloed
21
even slightly underestimated. Gabert and Sauer 1992a, where 500 FTU kg
generated 0.80 g 1994 reviewed that supplementing diets for weanl-
digestible P. In the diets without microbial phytase, ing pigs with organic acids increased nutrient and
both organic acids had a positive effect on the energy digestibilities up to 4-units. For growing
digestibility of P, which was 4.9-units and equal to
21
pigs 20 to 40 kg, Partanen and Mroz 1999 0.2 g digestible P kg
. However, there was a reported improvements of digestibility of nutrients,
significant interaction between phytase and acids, in particular on protein and energy, which seems to
which showed to be synergistic. The formic acid, but depend on the type and level of acid applied. The
not lactic acid, in combination with microbial improvement in digestibility they observed in grow-
phytase showed a further positive effect equal to ing pigs by the addition of organic acids was
4.9-units. Also, Kemme et al. 1999 reported that 1.0161.07 and 0.9460.54-units, respectively n 5
in pigs fed a maize–soybean meal diet a synergistic 8. The improved performance and digestibility as
effect of lactic acid and microbial phytase was affected by organic acids may be due to 1 lowered
found, being equal to 8.1-units or 0.24 g digestible
21
pH resulting in a higher dissociation of the mineral P kg
. Although Radcliffe et al. 1998 could not compounds, 2 reduced rate of gastric emptying, 3
show a significant interaction between microbial formation of chelated mineral complexes, that are
phytase and citric acid, a numerical increase in the easily absorbed, and 4 improved gut health of the
digestibility of P was found in the diets with animals because some are effective antimicrobials
microbial phytase and citric acid. The difference in Kirchgessner and Roth, 1982; Ravindran and Kor-
effects of lactic acid and formic acid in combination negay, 1993; Partanen and Mroz, 1999.
with microbial phytase between this experiment and of Kemme et al. 1999 needs to be further clarified.
21
4.3. Apparent total tract digestibility of Ca and P The dose of 32 g kg
lactic acid, however, had the same acid equivalency as the 30 g kg lactic acid in
In this experiment, no interaction was observed the experiment of Kemme et al. 1999 due to water
between microbial phytase and organic acid on the inclusion in the current preparation. So far, we
digestibility of Ca. Microbial phytase and the organic cannot exclude that this difference may derive from
acids enhanced the digestibility of Ca by 7.2 and the fact that lactic acid in the current experiment was
5.9-units, respectively. This increase is equal to in
D
-lactic acid, whereas
L
-lactic acid was applied in
21
0.39 and 0.32 g digestible Ca kg diet, respectively.
the experiment of Kemme et al. 1999. However, When expressing the effect of microbial phytase on
we have not analysed the lactic acids for their optical the digestibility of Ca in terms of the ratio of
isomerism, and no indication was found in the
A .W. Jongbloed et al. Livestock Production Science 67 2000 113 –122
121 Bos, K.D., Jetten, J., Schreuder, H.A.W., Venekamp, J.C., 1993.
literature about the impact of stereoisomerism of
Enzymatische bepaling van inositolfosfaat in veevoedergrond-
lactic acid on digestion and performance on pigs.
stoffen. In: Rapport TNO-Voeding nr. B 93.105.
The experiments showed that the positive effect of
Cromwell, G.L., Coffey, R.D., Parker, G.R., Monegue, H.J.,
the organic acids on the digestibility of Ca and P was
Randolph, J.H., 1995. Efficacy of a recombinant-derived phytase in improving the bioavailability of phosphorus in
similar at both supplementation levels. An open
corn–soybean meal diets for pigs. J. Anim. Sci. 73, 2000–
question still remains at what level of supple-
2008.
21
mentation of organic acids below 8.0 g kg , as used
CVB, 1996. Verkorte tabel. Voedemormen landbouwhuisdieren en
in this study, equally enhanced response to digestion
voederwaarde veevoeders. In: CVB-reeks nr. 20. Centraal Veevoederbureau, Lelystad, The Netherlands.
and growth will be maintained.
¨ Dungelhoef, M., Rodehutscord, M., 1995. Effects of phytase on
¨ ¨
the digestibility of phosphorus in pigs. Ubers. Tierernahrg. 23, 133–157.
Easter, R., 1988. Acidification of diets for pigs. In: Haresign, W.,
5. Conclusions
