Hi, I’m Laia Blavi and I’m a postdoctoral researcher in the Stein Monogastric Nutrition Laboratory
at the University of Illinois. Today I will be talking about the effect of a novel phytase on growth
performance, bone ash, and calcium and phosphorus digestibility in diets fed to growing pigs.

Corn is one of the most important feed ingredients in swine diets, and between 60 to 70% of the
total phosphorus is bound to phytate. Phytate is a mixed salt of phytic acid and consists on a
myo-inositol ring with six phosphates. Phytic acid may form insoluble salts with several divalent
cations such as calcium, zinc, iron, etc. Therefore, phytate can inhibit the absorption of these
minerals. In addition, phosphorus in this form is not available for pigs and poultry, because they
don’t have enough endogenous phytase. Therefore, swine and poultry diets are supplemented with
inorganic phosphorus, like monocalcium phosphate or dicalcium phosphate. But high phytate-phosphorus
excretion in manure is a potential source of environmental pollution.

To reduce the problems that I mention before, we can add phytase in the diets. Phytase hydrolyzes
the phosphomonoester bond of phytate and releases the phosphorus and also the other minerals like
calcium. Therefore, phytase increases the digestibility of phosphorus and calcium. Phytases are
found in plants, animal tissues and microorganisms, like bacteria, fungi and yeast.

Microbial phytase is commonly used as a feed additive and is produced by fermentation, which
requires special care in feed processing and diet formulation. Therefore, the industry has been
looking for an alternative phytase that could be cost-effective. One of these alternative strategies
is producing genetically engineered livestock to secrete phytase in saliva. However, pigs GMO are
not highly accepted by the consumers. Another strategy is producing transgenic crops that express
low phytate levels or microbial phytase. However, crops that express low phytate levels have
problems with germination because phytate is necessary for it.

Therefore, of all the strategies mention before, only crops expressing microbial phytase is a viable
strategy today. Corn is an attractive source for the production of transgenic plants expressing
phytase since it does not require extreme heat during postharvest processing, unlike soybean and
canola. The transgenic plant expressing phytase is generated by microbial phytase-encoding genes
with desired properties cloned and inserted in order to yield increased levels of phytase. So, we
will have corn with phytase expressed in the grain, and then the grain is milled and is ready for
use as a feed additive. 

Therefore, the objective was to determine the effect of graded levels of the novel corn-expressed E.
coli phytase GraINzyme in diets fed to weanling pigs on growth performance, bone ash, bone calcium
and phosphorus, and the digestibility of calcium and phosphorus.

To carry on this trial, we used a total of 60 weanling pigs with an initial average body weight of
10.78 kg. Pigs were randomly distributed to six dietary treatments, so we had ten pigs per
treatment. The diets were based on corn and soybean meal and contained titanium dioxide as an
indigestible marker. The six dietary treatments were the positive control diet, the negative control
diet and the negative control diet plus 500, 1000, 2000 and 4000 FTU of graINzyme.

In the positive control diet, all nutrients were supplied according to the recommendations of NRC
2012. 

The negative control diet was similar to the positive control diet with the exception that inclusion
of calcium was reduced 0.20 percentage units, and inclusion of phosphorus was reduced by 0.18
percentage units.

The rest of the diets were similar to the negative control diet but with 500, 1000, 2000 and 4000
units of phytase included.

Diets were offered on ad libitum basis. Pigs’ weights were recorded at the beginning of the
experiment and on the last day of the experiment, day 28. Feed intake was recorded during all trial
in order to calculate the average daily feed intake. During the last three days of the experiment, a
fecal sample was collected from all pigs by anal stimulation. On the last day of the experiment, all
pigs were euthanized and the right femur was removed to analyze the bone ash, bone calcium and bone
phosphorus.

I will start explaining the results of growth performance. All the results I will present follow the
same pattern. In the X axis, it is represented the six dietary treatments: the positive control,
negative control, and the negative control plus 500, 1000, 2000 and 4000 FTU. And in the Y axis, it
is represented the variable response, in this case the body weight. The orange bars represent the
initial body weight and the blue bars represent the final body weight. There were no differences
among treatments in the initial body weight. However, there was a reduction in final body weight of
pigs fed the negative control diet compared with pigs fed the positive control diet. But the
addition of phytase in the negative control diet increased quadratically the final body weight. So,
there were no differences between pigs fed the negative control diet plus 4000 FTU and pigs fed the
positive control diet.

The results of average daily gain are represented with the orange bars and the results of average
daily feed intake are represented with the blue bars. Pigs fed the negative control diet had lower
average daily gain and average daily feed intake compared with pigs fed the positive control diet.
The addition of phytase increased linearly the average daily feed intake and quadratically the
average daily gain. So, there were no differences between pigs fed the positive control diet and
pigs fed the negative control diet plus 4000 FTU of GraINzyme.

The gain to feed ratio results follow the same pattern. Pigs fed the negative control diet had lower
gain to feed ratio than pigs fed the positive control diet. Gain to feed ratio increased linearly as
the concentration of phytase added to the negative control diet increased. And there were no
differences between the positive control diet and the negative control diet plus 4000 FTU of
GraINzyme.

Now I will show the results of total amount of bone ash, bone calcium and bone phosphorus. Bone ash
is represented in the light blue bars, bone calcium in the orange bars and bone phosphorus in the
dark blue bars. Pigs fed the negative control diet had lower total amount of bone ash, bone calcium
and phosphorus compared with pigs fed the positive control diet. Bone ash, bone calcium and
phosphorus linearly increased as the concentration of phytase added to the negative control diet
increased. So, there were no differences between the positive control diet and negative control diet
plus 4000 FTU of GraINzyme.

And finally, the results of apparent total tract digestibility of calcium, represented in orange
bars, and phosphorus in blue bars. There was a reduction in apparent total tract digestibility of
calcium and phosphorus of pigs fed the negative control diet compared with pigs fed the positive
control diet. The addition of phytase increased quadratically the apparent total tract digestibility
of calcium and phosphorus when added to the negative control diet. And pigs fed the negative control
diet plus 4000 FTU of graINzyme had higher ATTD of calcium and phosphorus compared with pigs fed the
positive control diet.

Therefore, the conclusions are: Addition of GraINzyme to the negative control diet increased the
growth performance, the total amount of bone ash, bone calcium and bone phosphorus and the apparent
total tract digestibility of calcium and phosphorus. And 4000 FTU of GraINzyme phytase allows for
reduced added phosphorus and calcium.

The take home message is that GraINzyme is an effective phytase that may be used to reduce added
inorganic calcium and phosphorus in diets for weanling pigs.

And with that I would like to thank Agrivida for the financial support, and my fellow lab members.
If you enjoyed this presentation and you would like to know more about this topic, or want to learn
more about nutrition, you can visit our web site at nutrition.ansci.illinois.edu. Thank you for your
attention.