Slide 1
Hi. My name is Caroline Gonzalez-Vega, and I am a Master's student at
the University of Illinois in the Stein Monogastric Nutrition
Laboratory. And today, it's my pleasure to talk about determination of
endogenous intestinal losses of calcium in canola meal fed to growing
pigs.
Slide 2
So this is the outline of this presentation. First I would like to talk
about endogenous losses, and then I will mention the objective of the
experiment, the materials and methods that we used, also the results and
the discussion, and finally some conclusions.
Slide 3
This is a picture of the gastrointestinal tract of a pig to explain the
definition of endogenous losses. So the green circle represents the
nutrients in the feed, and the red stars represent the nutrients of
endogenous origin that have been secreted into the gastrointestinal
tract.
Slide 4
Some of the nutrients that have been endogenous secreted are reabsorbed,
but those nutrients that have not been digested and reabsorbed before
excretion are considered endogenous losses.
Slide 5
So the endogenous losses will be excreted with the nutrients from
dietary origin that were not absorbed by the animal.
Slide 6
So now let's see why endogenous losses are important to consider. For
apparent total tract digestibility, abbreviated as ATTD, may not be
additive in mixed diets if there is an endogenous loss of the nutrient,
because ATTD values are influenced by endogenous losses. On the other
hand, true total tract digestibility values, abbreviated as TTTD, are
additive in mixed diets, but to calculate TTTD, it is necessary to
correct apparent digestibility values for total endogenous losses.
Slide 7
It has been demonstrated that there is endogenous losses of amino acids
and phosphorus. However, there are not definitive data on whether or not
there is endogenous losses of calcium from pigs, and also there is not
information about if adding phytase to the diets has an impact on
endogenous losses of calcium. So the problem here is that we don't know
if apparent digestibility values of calcium are accurate to use, but if
in fact there is endogenous losses of calcium, apparent digestibility
values are likely not additive and therefore we expect that by
correcting apparent digestibility values by the endogenous losses of
calcium to calculate the true digestibility, these values will be
additive and therefore will be more accurate to formulate mixed diets.
So that is why we need more research in this area.
Slide 8
So our hypothesis for this study was that endogenous calcium is lost
from the gastrointestinal tract of growing pigs, and therefore, values
for true digestibility of calcium are different from values for apparent
digestibility of calcium. And the objective was to determine the
apparent digestibility and true digestibility of calcium in canola meal
with and without added microbial phytase.
Slide 9
For this experiment, we used 48 growing pigs with initial body weight of
16.7 kg, housed individually in metabolism cages. Also, the pigs were
allotted to a randomized complete block design with 8 treatments, and we
collected fecal samples using the marker-to-marker approach.
Slide 10
So we have 8 diets, all diets contain canola meal as the only source of
calcium. Four diets did not contain phytase, and these are represented
by the orange color. The other four diets contained 1,500 units of
phytase, and are represented by the blue color. We used microbial
phytase from E. coli from AB Vista, and this phytase is thermostable. In
each group of diets, we had four different levels of calcium lower than
the requirement to make sure we stay on the linear portion of the
response curve. And these levels were 0.08, 0.16, 0.24, and 0.32.
Slide 11
The reason that we used canola meal for this experiment was because we
were looking for a plant ingredient that was high in calcium and also in
phytate,. And we found that canola meal has 0.66% of calcium which is
pretty high for a plant ingredient, and also contains 2.58% of phytate.
Also we were looking for protein ingredients that we can use without
adding more calcium to the diets, and we found that corn gluten meal and
potato protein have 0.02% and 0.03% of calcium respectively.
Slide 12
So here we have a table with the composition of the diets. To increase
the level of calcium in the diet, we increase the inclusion level of
canola meal and reduce the amount of corn gluten meal, potato protein
and cornstarch and monosodium phosphate to maintain the protein and
phosphorus level constant. We used monosodium phosphate as source of
phosphorus instead of mono or dicalcium phosphate to avoid more
inclusion of calcium. The other four diets were similar to these four,
but 0.03% of phytase was included at expense of cornstarch.
Slide 13
We calculated the apparent and true digestibility values of calcium of
the diets. To estimate the endogenous losses of calcium we used the
regression procedure. And for this procedure we regress back to zero the
calcium intake. And we analyzed the data as a 4 x 2 factorial using Proc
MIXED procedure in SAS.
Slide 14
Now let's move into the results.
Slide 15
First let me set up the slide. In the x axis we have the level of
calcium expressed as percentage, we have the four levels of calcium
under the requirement and these are 0.08, 0.16, 0.24, and 0.32%. In the
y axis we have the calcium intake in grams per day. The blue bars
represent the canola meal diets without phytase and the orange bars
represent the canola meal diets with phytase. On the top we have the
P-values for the calcium level, phytase, and the interaction. The
P-values in red are significant. So here we observed that calcium level
was significant, which means that by increasing the level of calcium in
the diet, calcium intake also increased. And phytase did not have an
effect on calcium intake.
Slide 16
For total fecal calcium output in grams per day, the P-values for
calcium level, phytase, and the interaction between calcium and phytase
were significant. And because we got a significant interaction, this
means that we have two different slopes in the response, which means
that the total fecal calcium output increased as calcium level in the
diets increased. However, there is less calcium excreted when phytase is
included in the diets compared to the diets that phytase was not
included.
Slide 17
For apparent digestibility of calcium expressed as percentage, calcium
level was significant, which means that by increasing the level of
calcium, the apparent digestibility of calcium increased. And phytase
was also significant, so the diets that contained phytase had greater
apparent digestibility of calcium than the diets that did not contain
phytase.
Slide 18
And as I mentioned before, we used the regression procedure to determine
if there was endogenous losses of calcium. But let me first set up the
slide. In the x axis we have the dietary calcium intake in g/kg dry
matter. And in the y axis we have the apparent total tract digested
calcium in g/kg dry matter intake. The orange line represent the canola
diets without phytase and the blue line represent the canola meal diets
with phytase. By using the regression procedure we obtained two linear
equations. The negative intercept represent the endogenous losses of
calcium expressed in g/kg dry matter intake, and the slope represent the
true digestibility of calcium. And we also got an R-square. So for the
canola meal diets without phytase, we got a negative intercept of 0.16
and also we got a slope of 0.46 which means that the true total tract
digestibility of calcium in canola meal is 46%. Regarding to the canola
meal diets with phytase, we got a negative intercept of 0.19. Also we
got a slope of 0.70, which means that the true total tract digestibility
of calcium in canola meal when phytase is added to the diets is 70%. So
the two intercepts that we got from these two linear equations represent
the endogenous losses of calcium: 0.16 for the canola meal diets without
phytase and 0.19 for the canola meal diets with phytase. We test if
these two values were different from each other, and they were not
significantly different. Therefore, microbial phytase does not have an
impact on endogenous losses of calcium in pigs.
Slide 19
So once we determined that there was endogenous losses of calcium, we
were able to correct the apparent digestibility values by the endogenous
losses to calculate the true digestibility values of calcium. Remember
before, the values of apparent digestibility of calcium change as we
increase the calcium level, but it is not significant anymore with the
true digestibility values. This is a similar concept that we have seen
in phosphorus. And because of this, apparent digestibility of calcium
are likely not additive and we expect that true digestibility values are
additive. The true digestibility of calcium was increased when phytase
was added to the diets from an average 48.2 to 68.8, close to the values
obtained in the linear equations -- 46 and 70, respectively. And no
significant interaction between calcium and phytase was observed.
Slide 20
So with this, we conclude that endogenous calcium is lost from the
gastrointestinal tract of growing pigs. And therefore, apparent
digestibility values are different from true digestibility values for
calcium. Also we conclude that values for apparent digestibility of
calcium are influenced by the level of dietary calcium, but that is not
the case for values for true digestibility of calcium.
Slide 21
And finally, we conclude that microbial phytase increases the apparent
and true digestibility of calcium in canola meal, but it does not
influence the endogenous losses of calcium.
Slide 22
And with this, I want to thank you for your attention. And also we want
to thank AB Vista for the financial support. And for more information on
this and other topics related to monogastric nutrition, you can visit
our website: nutrition.ansci.illinois.edu. Thank you once again.