Hi everyone. My name is Diego Andres Lopez. I'm a second-year student in Dr. Stein's
group, and today, I will talk about the mineral composition of commercially available feed
phosphates. 

As an introduction, phosphorus is the second most abundant mineral in the body, and to be
delivered to pigs, we have two options. Use plant ingredients, which have a low
digestibility of phosphorus, and this is due to the presence of phytate. Phytate is the
natural storage of phosphorus in plants and is a molecule that needs to be broken down
with the use of an enzyme called phytase. But phytase does not occur naturally in the
gastrointestinal tract of the pigs. The second way to deliver phosphorus is by using
inorganic sources of phosphorus that have a high digestibility of phosphorus. Some of the
ingredients that we can use for this purpose are monocalcium phosphate, monosodium
phosphate, magnesium phosphate, and from now on I'm going to refer as MCP for monocalcium
phosphate, MSP for monosodium phosphate, MgP for magnesium phosphate, and DCP for
dicalcium phosphate. 

First, the production process of feed phosphates will start with the raw material of
phosphate rock, and this can have two different origins: sedimentary or volcanic. The main
difference between those two origins is the presence of different minerals: in the case of
sedimentary, we will observe mainly francolites, whereas in volcanic we can find
fluorapatites and hydroxyapatites. And the difference between these three minerals is the
composition or the presence of impurities. As you can tell in francolites we can observe
more minerals, and it's important to notice that carbonates can decrease the concentration
of phosphates, and this could decrease the concentration of phosphorus in the final
product.

After we obtain the phosphate rock, it can be treated with sulfuric acid to produce
phosphoric acid, and then phosphoric acid will be used in a second reaction with calcium
carbonate to produce DCP and MCP. It is important to explain that DCP and MCP are names of
two ingredients but are also names of two molecules. And in this case, this reaction will
occur from calcium carbonate and phosphoric acid to produce DCP, but if the reaction
continues, we will produce MCP. This will be explained more in depth later. 

Therefore, the objective of this experiment was to test the hypothesis that the production
process of feed phosphate will yield a product with a required concentration of
phosphorus, low impurities, and a low concentration of potentially harmful minerals. 

For this experiment, we procured seven sources of MCP, four sources of DCP, two sources of
MSP, and one source of MgP. And in these 14 feed phosphates, we analyzed macro minerals
such as phosphorus, calcium, potassium, sodium, magnesium, and sulfur; micro minerals such
as cobalt, copper, fluorine, iron, manganese, zinc; and for potential harmful minerals, we
analyzed aluminum, arsenic, cadmium, mercury, lead, and silicon. 

First, I will show you the concentration of phosphorus that we obtained from these feed
phosphates. And in this slide, you will find the concentration of phosphorus in MCP in
blue bars, the concentration of DCP in orange bars, and the concentration of MSP in gray
bars, also, the concentration of MgP in yellow bars. For MCP, what we can observe is an
average of 21.91% with a standard deviation of 0.86, which is good because the regulation
in the United States indicates that MCP has to have a concentration of phosphorus of at
least 21 percent; but since MCP1 and MCP3 were obtained from Europe, this legislation does
not apply, and that's the reason why they have a higher concentration of phosphorus. In
the case of DCP, we obtained an average of 19.18% with a standard deviation of 0.29, which
represents a low variation. And these results were above the minimum required for DCP,
which is 18.5% of phosphorus. For MSP, we obtained results of phosphorus for both sources
that were above the concentrations reported in in previous data. And in magnesium
phosphate, we obtained a concentration of phosphorus below the concentrations reported in
previous data. 

Now, moving into the concentration of calcium, what we can observe is a low variability in
the concentration of calcium for MCP. And from DCP, we can observe that the variation is a
little bit higher.

Now, moving to an explanation of why we can observe these differences between the
concentration of phosphorus and calcium, we need to analyze the chemical structure of MCP
and DCP. As I said before, it is important to have in mind that TCP and MCP are names of
ingredients, but they are also names of molecules. And first, for dicalcium phosphate,
this molecule has a concentration of phosphorus of 22.8% and a concentration of calcium of
29.4%. In the process of production of MCP and DCP, DCP will be the first molecule to be
synthesized, and this is because the high concentration of calcium and phosphorus
available will react in a ratio of one and one—meaning that one calcium will be attached
to one phosphate group and two different oxygens. But as the reaction continues, we can
observe a decrease in the concentration of available calcium, and therefore two phosphate
groups will interact with the same calcium, having a higher concentration of phosphorus of
26.5% and a concentration of calcium of 17.1%. 

Then moving into the minerals that we analyze as impurities, we can observe that for MSP
and for MgP, the concentration of sodium and magnesium will be high respectively because
the source of minerals used in the production of these feed phosphates will be high in
sodium and magnesium. But for the concentration of magnesium in MCP and DCP, what we can
observe is a small concentration with a high variability, whereas for potassium we can
observe a low concentration with low variability. And for sulfur, we can observe a low
concentration with some variability, and this is due to the use of sulfuric acid in the
process of production of feed phosphates. 

Moving into micro mineral concentration, for the sake of time, I will not include all the
minerals that we analyzed, but I will show you the tendency of all the results. For
copper, we obtained low concentration with high variability. The same as for iron—low
concentration with high variability. In this case, monosodium phosphate concentrations
were non-detectable. It is important to notice that some of the minerals that I am showing
you can also interact with phosphates to create phosphate salts, such as iron and
aluminum. 

Now moving into potentially harmful minerals, for the results of aluminum, we can observe
again a low concentration with high variability. And it's the same for all other potential
harmful minerals, such as arsenic, which I'm showing in this case.

With all these concentration of minerals, we can draw a picture of a sample in our head
that will look something like this: a sample with a concentration of phosphorus, calcium,
magnesium, and all other minerals that I mentioned before. 

But in reality, what we can observe is something completely different. Yes, we'll have all
these minerals, but we can also find some elements that we cannot analyze, such as oxygen,
hydrogen, and carbon. And we also have to take into consideration that all these minerals
and elements will be interacting with each other, creating compounds such as monocalcium
phosphate; dicalcium phosphate; phosphate salts such as aluminum phosphate, ferrous
phosphate, magnesium phosphate, and monosodium phosphate; and also some molecules that
will not contain any concentration of phosphorus, such as calcium carbonate. And we can
also find some of the minerals interact in ways that we cannot predict without more
analysis. 

With all this in mind, we also calculated the phosphorus bound to impurities in the
sources of MCP that we used in this experiment, and for this I would like to set up my
slide. In first graph on the left, you will find the concentration of phosphorus bound to
impurities as the concentration of total phosphorus in the sample, whereas in the graph on
the right, you could find the phosphorus bound to impurities as a percentage of the total
phosphorus bound to impurities. Starting with ferrous phosphate which will be represented
in blue, then red will represent aluminum phosphate, yellow will represent magnesium
phosphate, black will represent sodium phosphate, purple will represent phosphoric acid,
and then the phosphorus bound to DCP will be represented in orange and the phosphorus
bound to monocalcium phosphate will be represented in blue. As you can observe, the
phosphorus bound to impurities is less than 10% in most of the samples except for
monocalcium phosphate number seven, and with a low variability on the impurities that we
can find. 

Moving into DCP, we also did the same process, and we obtained results for iron phosphate,
aluminum phosphate, magnesium phosphate, sodium phosphate, and monocalcium phosphate. And
in this case, we also include a molecule called hydrated dicalcium phosphate, which is a
molecule of DCP but interacting with a molecule of water. What we can observe is that
there is some higher variability on how phosphorus will be bound to MCP or DCP molecules,
but again, the impurities are in a low concentration. 

Now, doing the same process but calculating the calcium bound to impurities, we obtained
results for calcium fluoride in green, calcium sulfate in yellow, calcium carbonate in
red, and again the calcium bound to DCP will be represented in orange and the calcium
bound to MCP will be represented in blue. What we can observe here is that mainly the
calcium that will be bound to impurities will be bound to calcium carbonate, which is
expected since the process of producing MCP will be stopped after the product can reach a
concentration of phosphorus desired. 

Moving into the same calculations for DCP, we also observed the same molecules— calcium
fluoride, calcium sulfate, and calcium carbonate—and in this case we also include hydrated
dicalcium phosphate. As you can tell, the concentration of impurities are a little bit
less variable in DCP, mainly because the calcium carbonate in this case is more abundant. 

Now moving into my conclusions, we observed that the process to produce feed phosphate is
effective to remove most impurities, and this process will also yield a product with a
minimum concentration of phosphorus. Also, the concentration of potential harmful minerals
will always be below the levels of tolerance of these minerals in the animal. And then we
also observe that there is a variable concentration of other minerals. However, these
minerals are in a small concentration and since these feed ingredients are used in a low
concentration in the diets, this presence of minerals will not be harmful for the animal. 

With that, I would like to acknowledge Yara for the financial support of this project. 

I would like to say thank you also to all the people in the Monogastric Nutrition
Laboratory of Dr. Hans Stein, and if you are interested in nutrition or want to know more
about feed phosphate, please follow us or listen to our podcast. Thank you so much.