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.
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