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.