Hello, my name is Carly Rundle and today I will be presenting research conducted at the
University of Illinois in collaboration with DuPont Animal Nutrition investigating the
effects of increasing phytase dose to 1000 FTU/kg on phosphorus and calcium digestibility
in pigs fed diets without inorganic phosphorus.

Phytate is the main form of phosphorus found in plant feed ingredients including seeds,
nuts, legumes, and grains, with about 50 to 60% of phosphorus bound to phytate. This
phytate can form complexes with minerals including zinc, copper, manganese, calcium, and
iron and therefore reduces the digestibility and absorption of many minerals. As
phosphorous is a required nutrient with a crucial role in bone formation, acid base
balance, and general metabolic function, it is crucial that pigs obtain optimum levels of
phosphorous in the diet.

Phytase is an enzyme that catalyzes the release of phytate complexes. However, intrinsic
concentration of phytase is very low in corn and legumes – common ingredients in diets fed
to pigs in the United States. There is also some phytase expressed in the gastrointestinal
tract of pigs, which may result in additional cleaving of the phytate to yield available
phosphorous and calcium for absorption by the pig. However, this is not enough for optimal
utilization of feed ingredients. As a result, exogenous microbial phytase produced on a
large scale through cellulosic biomass fermentation is added to diets fed to pigs to
maximize digestion and absorption of phosphorous in order to reduce feed costs associated
with including inorganic sources of phosphorus.

This increase in digestion and absorption of phosphorous has been shown to improve the
growth performance of pigs, including increases in average daily gain and the gain to feed
ratio, and it has also been shown to improve bone strength and bone density, resulting in
an improvement in overall health of the animal. Including phytase in diets fed to pigs may
then result in a reduction in feed cost, as organic sources of phosphorous including corn
and legumes are utilized more efficiently and lower amounts of inorganic phosphorous may
be included in the diet formulation. Another concern among producers and consumers alike
is the environmental impact of the diets fed to pigs. Considering the phasing out of
minerals such as zinc in livestock feed in the European Union, there is great interest in
investigating ways to reduce mineral deposition in manure to lessen the effects of
livestock production on the environment.

Inclusion of phytase in diets fed to growing pigs may improve the digestibility of calcium
and phosphorus, and subsequently reduce the environmental impact of mineral deposition in
manure through reduced fecal excretion. Therefore, it was the hypothesis of this study
that two sources of phytase, Buttiocella phytase from T. reesei or Phytase B as I will
refer to it throughout this presentation, and a hybrid phytase from A. niger or Phytase H,
would improve the digestibility and therefore decrease the fecal excretion of calcium and
phosphorus when included in diets fed to growing pigs.

There were 8 experimental diets in total. A positive control or PC diet based on corn,
wheat, canola meal, and soybean meal was formulated with monocalcium phosphate and
limestone to contain 0.29% digestible Phosphorous and 0.60% total calcium. The negative
control or NC diet was then based on corn, wheat, canola meal, and soybean meal and
formulated to contain 0.19% digestible phosphorous and 0.48% total calcium formulated with
limestone but without the inclusion of inorganic sources of phosphorus. Three additional
diets were formulated by adding either 250, 500, or 1000 FTU per kilogram of Phytase B
from Buttiocella phytase to the negative control diet, and another 3 diets were formulated
by adding either 250, 500, or 1000 FTU of phytase H from the hybrid phytase to the
negative control. 

80 growing barrows with an initial body weight of around 12.8 kilograms were allotted to a
randomized complete block design. The experimental period consisted of 12 days, in which
days 1-5 were considered an adaptation to the diet. An indigestible marker was fed on day
6, and fecal output was collected from the passing of the first marker until a second
indigestible marker fed on day 10 was passed. These samples were then dried in a
forced-air oven and finely ground prior to analysis. Diets, ingredients, and fecal samples
were then analyzed for calcium and phosphorus concentration in order to determine the
apparent total tract digestibility of these minerals. Apparent total tract digestibility
was calculated by subtracting the amount of each mineral in the feces from the amount
consumed in the feed and dividing that by the total amount of the mineral consumed in the
feed, multiplied by 100 to get a percentage value.

And now, moving on to the results from this experiment:

First setting up the graphs, on the X axis we have the PC and NC treatments in gray bars,
the phytase B treatments shown in blue bars with either 250, 500, or 1000 FTU, and the
phytase H treatments shown in orange bars with either 250, 500, or 1000 FTU. And on the y
axis is the dependent variable. This slide depicts the feed intake in grams per day, and
here we can see that there was no difference in feed intake among treatments.

When comparing both calcium and phosphorus intake in grams per day among treatments, there
was a decrease in intake from the PC to the NC diet, which is expected due to the
decreased calcium and phosphorus in the formulation of the negative control diet. There
were no differences in intake of calcium and phosphorus among the pigs fed diets
containing phytase. 

Next, looking at fecal excretion of calcium in grams per day, we observed that there was a
reduction in excretion of calcium from the PC to the NC diet, as expected. We also
observed both a linear and a quadratic reduction in the fecal calcium excretion as both
phytase sources were included, with the lowest excretion observed in the 1000 FTU
treatments. Comparing sources of phytase, it was also observed that phytase B reduced
excretion of calcium to a greater extent than phytase H.

Comparing the apparent total tract digestibility or ATTD of calcium in % among treatments,
we observed a slight increase in the digestibility of calcium in the NC diet compared with
the PC diet. Additionally, there is both a linear and a quadratic effect of both phytase
sources on the digestibility, with the greatest digestibility observed in the 1000 FTU
treatment for both phytase sources. Comparing sources, inclusion of phytase B resulted in
a greater digestibility than phytase H. The reduction in fecal excretion can largely be
attributed to the increase in ATTD observed on this slide.

Next looking at the fecal excretion of phosphorous in grams per day, we observed a
decrease in the excretion of phosphorus in the NC diet compared with the PC diet, as
expected. There was a linear effect of both phytase sources on the fecal excretion of
phosphorous, with the lowest excretion in the 1000-FTU treatments for both phytase
sources. Additionally, a quadratic decrease in the fecal excretion of phosphorus was
observed among phytase B treatments. Comparing the two sources of phytase, phytase B
inclusion resulted in a greater reduction of fecal excretion of phosphorus compared with
phytase H.

Comparing the ATTD of phosphorus in % among treatments, we observed no difference in the
ATTD of phosphorus between the PC and NC diets. There were both linear and quadratic
effects of the 2 sources of phytase, with the greatest digestibility of phosphorus
observed in the 1000-FTU treatments for both sources. Finally, comparing the two sources
of phytase, the ATTD of phosphorus was greater by the pigs fed the phytase B treatments.

From this experiment, we can conclude that both phytase B and phytase H increased the
apparent total tract digestibility of calcium and phosphorous and reduced fecal calcium
and phosphorous excretion in a dose-dependent manner, with phytase B having a greater
effect on increasing the digestibility of these minerals than phytase H, indicating that
both sources of phytase may be included in diets fed to growing pigs to improve the
utilization of organic sources of phosphorus compared with conventional inorganic sources
of phosphorus. Future research should be conducted in order to determine the optimum
levels of both sources of phytase in later stages of the growing phase and finishing phase
of production for maximum digestibility of calcium and phosphorus by pigs when included in
diets without inorganic sources of phosphorus.

I would like to thank DuPont Animal Nutrition for their financial support of this
experiment.

And with that, I would like to thank you for listening to my presentation, and if you
would like to know more about the research conducted in the Hans Stein Monogastric
Nutrition Laboratory, that information can be found at nutrition.ansci.illinois.edu.