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Good morning. I am Hans H. Stein, an associate professor in the Department of Animal Sciences
at the University of Illinois. And I'm here this morning to talk to you about some work
we have done recently in which we measured the energy concentration and phosphorus digestibility
in milk products fed to weanling pigs. This experiment was conducted by myself and my
two co-workers, Dr. Beob Kim and Jung Wook Lee, who is a graduate student here in the
Department of Animal Sciences.
The work I will talk about here will consist of a short introduction; I'll then talk about
an experiment we conducted to measure energy concentrations in the milk products, then
I will talk shortly about a project in which we measured the phosphorus digestibility in
the same three milk products, and then finally a few conclusions.
As a little bit of background, when milk is processed, we get different products coming
out of that processing procedure. First, if raw milk is made into cheese, the casein in
the milk and most of the fat is removed and going into the cheese. So what we are left
with is the whey, which consists of the lactose, a little bit of protein, and also the ash
that is in the milk. From that whey, the whey proteins can be removed to produce whey protein
concentrate, and that will leave us, then, with the whey without the whey proteins, and
that product is called whey permeat. The whey permeat consists mainly of lactose and ash;
and if the ash is removed from the permeat, then we will get a lactose product, or product
that contains mainly lactose.
If we look at the composition of three of these different products, then we can look
at whey powder as it's coming out of the cheese production and has been dehydrated, and that
product usually has 95.8% dry matter. It contains 3647 calories/gram of gross energy, there's
about 13% crude protein, 15 to 16% ash, and a little bit of calcium and phosphorus in
this product. Now, as I said before, whey protein concentrate can be produced from whey
powder by extracting the crude protein out of whey powder. And if that is done, we are
left with a permeat, and in this case we used a permeat called Perlac 850. And Perlac 850
is a typical permeat containing approximately 97.7% dry matter, 3426 calories/gram of gross
energy, and the protein is down to 4.3% because most of the protein was removed from the whey
powder. There's 8.96% ash left in the product, so some of the ash was also removed. And calcium
and phosphorus in this product is down to 0.42% and 0.57%. The last product we used
was called Variolac 960, and Variolac 960 is produced by removing most of the ash from
the Perlac 850 product. And now we have a product that contains 98.4% dry matter, 3657
calories/gram of gross energy, a little over 3% crude protein, and only 1.7% ash. And then
calcium and phosphorus here is down to 0.11% and 0.10% because most of the ash was removed.
So, from this it appears that the majority of the dry matter in Variolac 960 is lactose.
So lactose in Variolac 960 is about 95 to 96%, whereas lactose in Perlac 850 is only
85% and lactose in whey powder is about 72%.
The objectives of the work we conducted here were to measure the DE and the ME in the three
whey products that I just showed. And we also wanted to measure the standardized total tract
digestibility, which is also called the STTD, of phosphorus in each of the three whey products.
In the first experiment, we measured energy concentrations in the three products.
In this experiment, we used 32 weanling barrows. They had an initial body weight of 9.2 kg.
And they were placed in metabolism cages as shown here in the picture. Each cage is equipped
with a feeder so we can measure the amount of feed that each pig is provided every day.
There is a slatted floor, and below that floor there is a screen so we can collect all the
feces from the pigs. Below the screen, there is actually a funnel so we can collect the
urine as well. And that allows us to calculate the digestible and the metabolizable energy
that we have in these diets. We used four different diets, and we had eight pigs per
diet.
The diets we used consisted of a basal diet, and we had a whey powder diet, Perlac 850
diet, and a Variolac 960 diet. The basal diet consisted of 60% ground corn, 28% soybean
meal, 8% fish meal, and 4% vitamins, minerals, a little bit of fat, and other products. We
then took 70% of the basal diet and 30% of each of the three whey products to formulate
our three test diets. So the whey powder diet consists of 70% basal diet and 30% whey powder,
the Perlac 850 diet consists of 70% basal diet and 30% Perlac 850, and Variolac 960
diet consists of 70% basal diet and 30% Variolac 960.
The results from this experiment...
Results are shown in this chart. We have the digestible energy and the metabolizable energy,
and these data are on an as-fed basis. The blue bars are for the digestible energy, and
the orange bars are for the metabolizable energy. Digestible energy is calculated by
subtracting the energy in the feces from the energy intake of the pig, and the metabolizable
energy is calculated by subtracting the energy in the feces and in the urine from the energy
intake of the pig. We have the amount of energy on the left-hand side here, and each of the
three whey products along the X-axis. For the whey powder product, we can see that the
digestible energy was 3494 calories/gram, whereas the metabolizable energy was 3313
calories/gram. The Perlac 850 product contained a little bit less energy, and there was 3177
calories/gram of digestible energy and 3009 calories/gram of metabolizable energy. And
both of these values were significantly lower than for the whey powder. However, when we
went to Variolac 960, we see that the energy increased compared with the Perlac 850, so
we had 3626 calories/gram of digestible energy in Variolac 960, and 3537 calories/gram of
metabolizable energy.
If we look at the data on a dry matter basis, we'll see that the whey powder contains 3646
calories/gram of digestible energy, and 3462 calories/gram of metabolizable energy. Perlac
850 contained 3253 calories/gram of digestible energy and 3081 calories/gram of metabolizable
energy. And Variolac 960 contained 3683/gram of digestible energy and 3593 calories/gram
of metabolizable energy. And we can see here again that the values for whey powder and
Variolac were significantly greater than the values for Perlac. And the reason we see an
increase in energy when we go to Variolac compared with Perlac is that the ash was removed
from the product.
In the second experiment, we measured the digestibility of phosphorus in the same three
whey products.
In this experiment, we used 32 barrows. In this experiment, the pigs weighed 11 kg at
the beginning of the experiment. And again, the pigs were placed in metabolism cages exactly
like before, but this time we collected only the fecal materials from the pigs and not
the urine. Again, we measured the feed intake of each pig and we collected the fecal materials
over a five-day period. We had four diets and eight pigs per diet in this experiment.
The diets we used were the diet based on whey powder, a diet based on Perlac 850, and a
diet based on Variolac 960, and we also had a phosphorus-free diet in this experiment.
The diet based on whey powder contained 44.5% cornstarch, 30% whey powder, and then there
was sugar, and soybean oil, and a few other ingredients included. All vitamins and minerals
were included in these diets to the recommended levels except that there was no phosphorus
added to the diet. So all the phosphorus in this diet came from the whey powder. Perlac
850 diet was formulated using the same principles again with 44.5% cornstarch, 30% Perlac 850,
and sugar and soybean oil and a few other ingredients. And for the Variolac 960 diet,
we used exactly the same composition and the only difference was that here the 30% whey
product was Variolac 960 instead of Perlac 850. Again, in all of these three diets, the
only phosphorus in each diet was provided by the whey product itself. We used a phosphorus-free
diet that consisted of 29.2% cornstarch, 20% lactose, 20% sugar, soybean oil, and 26.8%
other ingredients, and 20% of these other ingredients was actually gelatin, which is
a phosphorus-free source of amino acids. We also had quite a few synthetic amino acids
in this diet to make it as balanced as possible. The resason for using the phosphorus-free
diet is that by feeding the phosphorus-free diet, we could measure what the excretion
of phosphorus from the pigs were if they were fed no phosphorus, and we could use those
values to correct the data from the other three diets.
Results from this experiment...
The results are shown in this chart, where we have the digestibility of phosphorus in
each of the three products. The blue bars represent the apparent total tract digestibility
of phosphorus and the orange bars represent the standardized total tract digestibility
of phosphorus. You see for the whey powder, the apparent total tract digestibility was
84.3 and the standardized total tract digestibility was 91.2%. For Perlac 850, the apparent total
tract digestibility was 86.1% and the standardized total tract digestibility of phosphorus was
93.1%. And in the Variolac 960 product, we had 55.9% apparent total tract digestibility
of phosphorus and 91.8% standardized total tract digestibility of phosphorus. So what
we see here is that when we look at the apparent total tract digestibility, we had about the
same values for whey powder and Perlac 850, but a much lower value for Variolac 960. However,
when we look at the standardized total tract digestibility, there were no differences among
these three products. The reason we get a different result when we look at the standardized
total tract digestibility compared with the apparent total tract digestibility is that
all values for the standardized total tract digestibility are corrected for the losses
of phosphorus from pigs that were fed the phosphorus-free diet. And by correcting for
these losses, we get a little bit greater value in all products for the digestibility,
but this correction means a lot more for Variolac 960 than for the other products. And the reason
for this is that the concentration of phosphorus in Variolac 960 is lower than in the other
products and therefore, the correction for endogenous losses increases the digestibility
proportionally much more than for the other products. This also illustrates why it is
more correct to formulate diets based on the standardized total tract digestibility of
phosphorus compared with the apparent total tract digestibility of phosphorus, because
the values for apparent total tract digestibility of phosphorus are influenced by the endogenous
losses, which is not the case for the values for the standardized total tract digestibility
of phosphorus. But again, overall for all three products, we saw a very high digestibility
of phosphorus above 90% on a standardized total tract digestibility basis, and this
is much greater than what we will find when we look at vegetable feed ingredients. So
all three products are excellent sources of digestible phosphorus.
A few conclusions that we can draw from these two experiments ...
We have seen that the metabolizable energy on an as-fed basis was 3317 calories/gram
for whey powder. That was greater than in Perlac 850, which was only 3009, but the whey
powder had a similar ME value compared with the Variolac 960 product at 3537 calories/gram.
All three products can be used in diets fed to pigs, but if Perlac 850 is used, we have
a little bit less energy compared with using whey powder or Variolac 960. For phosphorus,
we saw that the digestibility on the basis of standardized total tract digestibility
was 91.2, 93.1, and 91.8% in the three products. If we convert that to percent of standardized
total tract digestible phosphorus in the products, we can do that by multiplying the digestibility
values for phosphorus by the total concentration of phosphorus in the products. And when we
do that, we see that we have 0.57% standardized total tract digestible phosphorus in whey
powder, we have 0.53% in Perlac 850, but we have only 0.09% in Variolac 960. So with these
data, we can formulate diets for weanling pigs using either whey powder, Perlac 850,
or Variolac 960. Each of these products are supposed to be valuable products in weanling
pigs' diets, and now we have data for both the metabolizable energy concentration and
the standardized total tract digestibility of phosphorus in these diets.
I'd like to thank you for your attention. I hope you find this information interesting,
and I would like to draw your attention to our website, where you can find a lot more
information about nutrient digestibility in different feed ingredients and many other
issues related to swine nutrition.