Hello. My name is Laura Merriman, and today I will be discussing some research
that was conducted at the University of Illinois Swine Research Farm. The title
for today's presentation is "The effect of microbial phytase on the apparent and
standardized total tract digestibility of calcium in feed ingredients of animal
origin fed to growing pigs." 

The outline for this presentation is as follows. I'll first begin with the
introduction on the digestibility of calcium in feed ingredients and the use of
microbial phytase in feed ingredients of animal origin. I will then state the
objective of the experiment, provide you with the materials and methods, and
then state the results for the digestibility of calcium and phosphorus in the
ingredients of animal origin, and the effect of adding microbial phytase. I will
then leave you with some conclusions and take home messages.

The current version of the NRC comes to us from 2012 and provides us some
requirements for calcium and phosphorus.

Across the top row, we have the body weight expressed in kg. I have shown here
the requirements for the smallest pig at 7-11 kg up to the finishing pig at
100-135 kg body weight. The requirements for phosphorus are expressed on a total
phosphorus basis as well as the standardized total tract digestible phosphorus,
which is a more accurate depiction of the pig's requirements. You can see that
the requirements for total phosphorus and standardized total tract digestible
phosphorus are reduced as the body weight of the pig increases.

However, when it comes to calcium, the requirements provided by the NRC are only
available on a total calcium basis. But we observe a similar pattern from
phosphorus, that requirements decrease as the body weight of the pig increases.

These total calcium requirements were computed using a ratio of total calcium to
standardized total tract digestible phosphorus at 2.15:1.

It was stated that the NRC would have preferred a ratio that would have been
between digestible calcium and digestible phosphorus. However, due to a lack of
data, that was not possible. In order to calculate diets on a digestible basis,
it is essential that the digestibility of calcium be estimated in ingredients.
Some work has already been conducted to determine digestibility of calcium in
feed ingredients, and I will present all of the available data at this time.

First, I will present the digestibility of calcium in plant ingredients. I will
first set up the slide, which will be the same format as subsequent slides.
Across the top row, we have calcium expressed as total calcium in the
ingredient. Then we have the apparent total tract digestibility of calcium and
the standardized total tract digestibility of calcium in that feed ingredient.
For the plant ingredients, which I have highlighted in green, I have corn,
canola meal, and soybean meal. And again, theses are the only values available
to us in the literature. And the calcium concentration in these ingredients is
quite low. We have 0.02 in corn, 0.69 in canola meal, and 0.35% in soybean meal.
We see that the digestibility of calcium is quite low in these plant
ingredients. The digestibility of calcium on apparent basis is between 35 and
49%. However, when we look at the standardized total tract digestibility, we
only have canola meal values available, and that was at 49%.

Now, keep in mind that canola meal and soybean meal contain relatively high
concentrations of calcium compared with other plant ingredients. And also keep
in mind that soybean meal may have a variable concentration of calcium as some
include limestone in the soybean meal to increase the flowability of that
product.

Now in the bottom half of this table, in white, we have the inorganic
supplements. We can see that the concentration in these ingredients is much
higher. We have dicalcium phosphate, monocalcium phosphate, and limestone. And
the calcium concentrations between 17 and 36% in these ingredients. The
digestibility of calcium is also much higher in these ingredients: between 72
and 83% on apparent digestibility of calcium, and then 78 to 86% for
standardized total tract digestibility of calcium.

Now I have represented in blue the feed ingredients of animal origin. Now, keep
in mind, this is all the available data that we have on these ingredients. Our
current data, we have fish meal, meat and bone meal, and meat meal. The calcium
concentrations in these ingredients are intermediate between those plant
ingredients and the inorganic supplements. And they contain between 4% and 11%
calcium. The digestibility of calcium in these feed ingredients of animal origin
are quite high: between 53 and 81% on apparent total tract digestibility terms.
However, we only have standardized total tract digestibility of calcium for fish
meal, at 76%.

The other component of this is how microbial phytase may impact the
digestibility of calcium in these ingredients of animal origin. One study was
conducted by González-Vega and others, and she had two diets. First was a basal
diet containing fish meal, corn, and corn germ, which contained no microbial
phytase. And then another diet that was similar to this except that it contained
500 units of microbial phytase. She presented findings for the apparent total
tract digestibility of calcium, standardized total tract digestibility of
calcium, and apparent total tract digestibility of phosphorus. And she observed
an increase in the digestibility of each of these with the addition of 500 units
of microbial phytase.

Keep in mind that these ingredients of animal origin do not contain phytate.
However, these ingredients, when in the stomach, combine with the phytate from
the plant ingredients, and therefore reduced performance can be observed even
though phytate is not present in these ingredients. The digestibility of calcium
may be improved by the addition of phytase with fish meal because the phytate
from plant ingredients binds to the calcium in the fish meal when present in the
stomach.

So after this data, we have a couple of questions. First, what is the
standardized total tract digestibility of calcium in the feed ingredients of
animal origin; and how will the addition of microbial phytase impact the
digestibility of calcium in animal proteins other than just fish meal?

And therefore, the objective of the present study was to determine the effect of
adding microbial phytase on the apparent and standardized total tract
digestibility of calcium in meat and bone meal, meat meal, poultry byproduct
meal, and poultry meal.

To answer our objective, we used 72 barrows with initial body weight of 14.91
kg. There were nine experimental treatments. The first treatment was a
calcium-free diet and was used to estimate the standardized total tract
digestibility of calcium in these feed ingredients. And then we had four
ingredients—the meat and bone meal, meat meal, poultry byproduct meal, and
poultry meal—either in the absence of phytase or the addition of 500 units of
microbial phytase. And each of these experimental diets was fed to eight
replicate pigs per diet.

In this experiment, pigs were individually housed in metabolism crates, and
total feces were collected using the marker to marker approach. Each period
lasted a total of twelve days. The first five days served as the adaptation
period to the environment and to the diet. And then on day 6, an indigestible
marker was added to the morning meal. And then on day 11, ferric oxide was
included in the morning meal to indicate the ending of collection.

For this experiment, we used the direct procedure and used the following
equation to calculate the apparent total tract digestibility: (nutrient intake –
nutrient output) divided by (nutrient intake) and multiplied by 100%.

And standardized total tract digestibility was calculated as (intake – output
with endogenous losses subtracted) divided by (intake) and again multiplied by
100%.

Now, I'd like to provide you with the analysis of the ingredients. Again, we
have meat and bone meal, meat meal, poultry byproduct meal, and poultry meal. We
can see here that these ingredients are a substantial source of protein. They
contain between 50 and 75% crude protein.

However, the ash content is quite high. Meat and bone meal and meat meal contain
approximately 25% ash, and then the poultry byproduct meal and poultry meal
contain about 13%, indicating that the mineral content of these ingredients is
quite high.

This is evident by the concentrations of calcium. Meat and bone meal and meat
meal contain 8% calcium, and then 3.6% in poultry byproduct meal and poultry
meal at almost 4%.

Phosphorus content is also quite high in these ingredients as meat and bone meal
contains 4%, meat meal contains 2.96%, poultry byproduct meal contains 2.2%, and
poultry meal contains 2.3%.

Now I'd like to explain the composition of the diets. These were primarily corn
and potato protein diets. However, you'll see that the corn concentration does
vary a little bit, as we wanted the concentration of phytate to be equal across
all these diets. Also, these ingredients contained crude protein, and so potato
protein was adjusted to keep the concentration of protein the same across all
diets.

Because calcium was supplied entirely by the test ingredient, the concentrations
of meat and bone meal, meat meal, poultry byproduct meal, and poultry meal were
different across the diets to provide the current requirement for calcium. And
so we see that the test ingredient was included at 8.5, 8.4, 15.25 and 24.5% for
each of the test ingredients.

Monosodium phosphate also supplied some of the phosphorus to get at that
requirement at 0.33 digestible phosphorus.

The other components of this diet include cornstarch, soybean oil, salt, and
vitamin-mineral premix.

For the statistical analyses of this experiment, we used the Mixed procedure of
SAS. The model contained the fixed effects of ingredient, phytase, and that
interaction between ingredient and phytase. Additionally, there was a random
effect of block, and the experimental unit was the pig. Significance was
observed when P-values were less than 0.05.

Now I'd like to set up the slides for the results. The blue bar indicates the
diet containing meat and bone meal, the red bar indicates the diet containing
meat meal, the green bar indicates the diet containing poultry byproduct meal,
and the purple bar indicates the diet containing poultry meal. Across the x-axis
you can see that I've displayed both in the absence of phytase and in the
addition of 500 units of microbial phytase. First, I would like to provide you
with the apparent total tract digestibility of calcium. And you can see that in
the absence of phytase, the diet containing poultry byproduct meal was greater
than the diet containing meat meal or meat and bone meal. However, in the
presence of phytase, there was no difference for the digestibility of calcium
among our dietary treatments.

Next, I have the standardized total tract digestibility of calcium. And we see
the same trend following here, where in the absence of phytase, digestibility of
calcium by pigs fed the poultry byproduct meal was greater than the pigs fed the
diets containing meat and bone meal or meat meal. However, when phytase was
added, there were no differences across our dietary treatments.

Now, I'd like to turn your attention to the apparent total tract digestibility
of phosphorus in the diets. And in the absence of phytase, there are no
differences across the dietary treatments. However, in the addition of microbial
phytase, pigs fed diets containing poultry byproduct meal had greater
digestibility of phosphorus than pigs fed the diets containing meat meal.

So previous work has demonstrated a significant increase in the digestibility of
calcium when phytase was added to a diet containing fish meal. But that was not
observed in the current study.

However, concentrations of phytate were greater in that previous experiment
compared to the present experiment.

And ingredients of animal origin may provide a significant portion of the
dietary calcium, and that calcium is highly digestible by growing pigs.

Furthermore, the digestibility of calcium and phosphorus in meat and bone meal,
meat meal, poultry byproduct meal, and poultry meal is not affected by the
addition of microbial phytase at 500 units/kg.

So the take home message from this experiment is that the addition of microbial
phytase did not affect the digestibility of calcium or phosphorus in ingredients
of animal origin, 

and only small differences in the digestibility of calcium and phosphorus were
observed among the four ingredients.

I would like to acknowledge Darling Ingredients for providing those animal
proteins, AB Vista for supporting this project, and if you'd like to see any
more work by our lab, please visit our website at nutrition.ansci.illinois.edu.
And thank you for listening to my presentation.