URBANA, Ill. — Phosphorus is a vital nutrient for pig
growth, but the majority of the phosphorus in common plant-based feedstuffs is
bound to phytate and, therefore, is unavailable to pigs.
Diets fed to pigs can be supplemented with microbial phytase
to improve phosphorus digestibility, according to Hans S. Stein, a University of
Illinois professor in animal sciences.
Stein and his team at the U of I recently published results
indicating that a new microbial phytase derived from the bacterium Aspergillus
oryzae is highly effective at releasing phosphorus from the phytate molecule.
“There are many microbial phytases on the market, and
companies are constantly developing new ones to try to release more phosphorus
from the phytate molecule,” Stein said. “Some are E. coli-based, and some are
based on other microbes. This particular enzyme is based on Aspergillus oryzae,
and this is the first time we have worked with it.”
In the study, pigs were fed diets based on corn and soybean
meal. The positive control diet had dicalcium phosphate and limestone added.
The negative control diet contained no microbial phytase and
no dicalcium phosphate, and experimental diets were formulated by adding 500,
1,000, 2,000 or 4,000 phytase units, respectively, to the negative control diet.
Two experiments were conducted: one using weanling pigs with
an average initial body weight of 13.5 kilograms and one using growing pigs with
an average initial body weight of 36.2 kilograms.
Stein explained that when the negative control diet was fed
to weanling pigs, the apparent total-tract digestibility of phosphorus was 40.5
percent. The ATTD of phosphorus increased as phytase was added to the diet, to a
maximum of 68.7 percent.
A broken line analysis was then performed to determine the
optimal phytase level. The breakpoint was at 1,016 phytase units, with an ATTD
of 68.4 percent. This compared favorably to the ATTD of phosphorus in the
positive control diet, which was 60.5 percent.
For growing pigs, the ATTD of phytase was 39.8 percent for
the negative control diet, 59.4 percent for the positive control diet, 72.8
percent at 4,000 phytase units and 69.1 percent at the breakpoint level of 801
Calcium digestibility also was improved by adding microbial
phytase to the negative control diet, the professor said.
In weanling pigs, the ATTD of calcium increased from 63.9
percent in the negative control to 84.7 percent at the optimal phytase level of
1,155 phytase units. In growing pigs, the ATTD of calcium increased from 67.3
percent in the negative control to 83.5 percent at the optimal phytase level of
574 phytase units.
“Because we did not compare this phytase to other microbial
phytases, we cannot say whether or not this is as good as or better than some of
the other commercial phytases, but this is a very effective phytase,” Stein
The new Aspergillus oryzae-based phytase, Ronozyme HiPhos,
is produced in Denmark and has been approved for use in Europe and the U.S.,
where it is marketed by DSM Nutritional Products.
The study, “Effects of a novel bacterial phytase expressed
in Aspergillus oryzae on digestibility of calcium and phosphorus in diets fed to
weanling or growing pigs,” was published in the Journal of Animal Science and Biotechnology
and is available online at www.jasbsci.com/content/4/1/8.