Valuing feed ingredients, 1/2: Feed ingredient composition
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Valuing feed ingredients, 1/2: Feed ingredient composition

October 18, 2019


Hello. I am Hans Stein from the University
of Illinois, and I will talk to you today about methodologies for evaluating quality
of feed ingredients. This is part of a presentation that I gave at the Midwest Animal Science
Meeting in Des Moines in March 2011. And today, I will present the first part of this presentation,
and talk about feed ingredient composition. The remainder of the presentation will be
recorded at a later time. So when we talk about nutrition in general,
we talk about three main areas. The first area we talk about is what we feed to the
animals. That means the composition of the feed ingredients that go into our diets — the
nutrients, the energies and so forth — and also the antinutritional factors and maybe
toxins if they are present. Those are all related to the feed ingredients that we use.
The second area of nutrition is what happens to these feed ingredients when they are ingested
by the animal and get into the GI tract. And here we talk about digestion, absorption,
and excretion of nutrients. And the third part of nutrition is what happens in the rest
of the body after the nutrients have been absorbed from the GI tract. They are metabolized,
new compounds are synthesized, compounds are deposited, and if there are any excesses,
they will be excreted. So, these are the three main areas of nutrition, and today I will
talk only about the first area. So when we look at the nutrient composition
of feed ingredients, we can actually learn a lot just from analyzing the concentrations
of nutrients in these feed ingredients. The first thing we usually look at is the moisture
level, or the dry matter concentration. And, obviously we want the dry matter to be as
high as possible because animals get nutrients and energy from the dry matter part, not from
the moisture part. And usually, most of our feed ingredients have a dry matter concentration
of 86-90% because at that dry matter level, they can be stored for longer periods of time.
If the moisture is greater than 10-14%, we usually have trouble storing our ingredients,
so we try to dry them down to 86-90% dry matter. The second thing we might want to look at
is the concentration of ash in our ingredients. The ash analysis is easy, and it’s inexpensive,
and it tells us a lot about the ingredient we have. And I’ll give an example of that
later. But, we have to remember that it’s in the minerals part that the calcium and
the phosphorus and other minerals are present. And we know that these minerals are needed
by the animal, so we do need to have an estimate of the concentration of calcium and phosphorus
and other minerals in the ingredients. However, we do not want high ash concentrations because
that will reduce the concentration of other nutrients, and also reduce the concentration
of energy in the ingredients. We talk about protein, we talk about amino
acids, and in particular the indispensable amino acids that are needed by the animals,
and we therefore have to analyze our ingredients for amino acid composition. Pigs don’t need
protein, they only need the amino acids. And we can have relatively high protein concentrations
without having high amino acid concentration, and we’ll talk a little bit about that in
a few minutes also. Carbohydrates is not something that we always
analyze ingredients for. However, depending on the ingredient we are looking at, it may
be important to analyze for starch, and if we do that, we should use an enzymatic procedure
to analyze starch because that procedure is the most accurate one. We may also want to
analyze for fiber, and here we can use ADF procedures, NDF procedures, or TDF procedures,
and all of these procedures will tell us something about the concentration of fiber in the ingredient,
and to some degree also about the nature of the fiber that we have in the ingredient.
In the old days, we used an analysis for crude fiber; however, that analysis is now recognized
as not being very accurate, so we usually don’t use that anymore. The last thing we analyze for is fat, and
when we do that, we prefer to use a procedure called acid hydrolyzed ether extract, and
that means that we acid hydrolyze our ingredients prior to extracting the fat with ether. And
this procedure will tell us the total concentration of fat in the ingredient. Sometimes, we may
also want to know the composition of that fat, and if that’s the case, then we need
to analyze for individual fatty acids in the fat. And this is important if we have vegetable
feed ingredients with relatively high concentration of fat, because some of these fatty acids
may have negative impacts on the product quality of pigs and can result in soft bellies and
soft backfat in pigs if they are fed these ingredients. This is an example of why it’s important to
analyze for ash in feed ingredients. In this case, we have two different products. Both
are called whey permeate. You will see what we call Whey-Permeate 1 contains 8.96% ash,
but what we call Whey Permeate-2 contains only 1.72% ash. And we can see how that influences
the concentration of metabolizable energy. We have that measured here in ME in kcal/kg
dry matter, and we can see that Permeate-1 contains 3081 kcal/kg dry matter, whereas
Permeate-2, with the low ash concentration, contains 3593 kcal/kg dry matter. So, this
illustrates why is it important to determine the ash concentration in these ingredients,
because they directly influence the amount of energy that the animal can get out of the
ingredients. Here’s an example of four different ingredients.
They are all co-products from the corn industry. And we have corn gluten meal, corn germ meal,
DDGS, and hominy feed. And listed here are concentrations of crude protein in the blue
bars, acid hydrolyzed ether extract (or fat) in the red bars, NDF, which is the fiber,
in the orange bars, and starch in the green bars. And we will see that corn gluten meal
is a high protein ingredient containing more than 60% crude protein. There is, however,
very little fat in corn gluten meal, there’s a little bit less than 30% fiber so it’s a
medium high fiber concentration, and there’s a low concentration of starch in this ingredient.
Corn germ meal contains much less protein, contains very little fat, but contains almost
50% NDF, which means the fiber concentration in this ingredient is very high. Starch is
relatively low as well. DDGS has a medium concentration of protein and relatively high
concentration of fat — about 10% — and a medium concentration of NDF or fiber also
— about 32%. Starch is relatively low in DDGS. However, when we look at hominy feed,
we have low concentration of protein, low concentration of fat, low concentration of
fiber, and high concentration of starch. So, we can see from this that although all four
ingredients here are co-products from the corn industry, they are very different in
terms of their nutritional concentrations. And therefore it is important to analyze the
ingredients to correctly characterize and estimate the nutritional value of these ingredients. Here’s another example of feed ingredient
evaluation. We have sunflower seeds and sunflower meal. And sunflower seeds in the blue bar
contains 54% crude fat, or ether extract, whereas sunflower meal contains only 1.6%.
And this is no surprise because sunflower meal is simply the meal that is left over
from sunflower seeds that have been defatted. So it’s produced by taking the fat out of
these sunflower seeds. However, things aren’t always as we expect
them to be. And we listed here on the left the concentrations of nutrients in sunflower
seeds: 54.5% acid hydrolyzed ether extract, or fat, as we saw before, 22.1% crude protein,
lysine is 0.79%, NDF is 8.1%, and moisture is 10%. If we take these values and we have
measured 1.6% fat in the sunflower meal, then we should be able to calculate how much crude
protein, how much lysine, how much NDF, and how much moisture is left in the sunflower
meal because the sunflower meal is simply the defatted sunflower seeds. And if we do
this calculation, we’ll see that we expect sunflower meal to contain 47.1% crude protein,
1.67% lysine, 17.3% NDF, and 10% moisture. However, we recently conducted experiments
with sunflower meal, and we got sunflower meal and sunflower seeds delivered to the
University of Illinois, and we can see the product we got delivered is listed here on
the right. And the acid hydrolyzed ether extract was 1.6%, as we had expected. However, crude
protein and lysine was only 29.4 and 1.01% respectively, and not 47.1 and 1.67% as we
had expected by calculating simply from the sunflower seeds. So, the delivered sunflower
meal was different from what we expected, and the reason we had this relatively low
concentration of crude protein and lysine in the delivered sunflower meal was that the
NDF was much greater than we had expected. You can see here we have expected NDF concentration
to be 17.3%; however, when we analyzed the sunflower meal, we had 39.3%. So we conclude
from this that it is important to analyze ingredients to know exactly what we have in
there, and sometimes things are not exactly what we expect. Here’s another example of why things need
to be analyzed. And I said before we need to analyze for amino acids, not only crude
protein, to evaluate the crude protein portion of the feed ingredient. We have here three
feed ingredients: soybean meal, corn gluten meal, and DDGS. The crude protein concentration
in these three ingredients are 47.5% in soybean meal, 62.9% in corn gluten meal, and 27.5%
in DDGS. Lysine and tryptophan in soybean meal are 3.02 and 0.65% respectively. However,
corn gluten meal, which contained more crude protein than soybean meal, contains much less
lysine: only 1.18% versus 3.02% in soybean meal. And also much less tryptophan: 0.44%
versus 0.65%. So we can see here that although the crude protein concentration in corn gluten
meal is greater than in soybean meal, the concentration of amino acids is actually much
lower. And the same is true for DDGS. We have a lower crude protein concentration in DDGS
compared with soybean meal, but also a much lower concentration of both lysine and tryptophan.
And to try to evaluate different feed ingredients, we can actually calculate each amino acid
as a percentage of the total crude protein concentration in that ingredient. If we do
that, we will get an understanding of the quality of the protein that we have in the
ingredient. And we can see here for soybean meal, lysine is 6.35% of the total crude protein,
whereas in corn gluten meal, it’s only 1.88%, and in DDGS it’s 2.84%. So, much lower concentration
of lysine as a percentage of crude protein in corn gluten meal and DDGS compared with
soybean meal. And we can see the exact same thing is true for tryptophan; we have a greater
concentration of tryptophan as percentage of crude protein in soybean meal compared
with corn gluten meal and DDGS. So the bottom line here is that it’s not enough to only
analyze for crude protein when we evaluate feed ingredients. We need to evaluate for
amino acids, and if we want to estimate the quality of the protein in our feed ingredients,
then it is a good idea to express the amino acids as a percentage of crude protein in
the ingredient, and compare ingredients that way. That will give us an estimate of the
protein quality in the ingredient. Another thing that may happen in feed ingredients
is that if they are heated or dried, they could be damaged, and that will result in
particular in problems for lysine and lysine digestibility; and this is something that
happens if sugars and proteins are heated together. And we get something that’s called
a Maillard reaction, and during this Maillard reaction, lysine will go through a series
of chemical reactions, and eventually give rise to products we call Amadori products
and melanoidins. Melanoidins are cyclic compounds that are completely indigestible, and give
no protein value to the animal. So the more lysine that has been turned into melanoidines,
the less is the concentration of lysine in that ingredient. Amadori compounds, however,
will to some degree reduce the lysine concentration, but may also reduce lysine digestibility.
So it follows from this that if we have heat-damaged feed ingredient, we have a lower digestibility
of lysine and a lower concentration of lysine in this ingredient. And this is because we
have part of the lysine that has been made unreactive or undigestible because of the
heat damage. We called that unreactive lysine, whereas part of the lysine is still reactive
because it was not heat damaged. And here’s an example of soybean meal that
was heat treated. You can see on the left we have a control soybean meal; we did not
heat treat that. The second sample of soybean meal had been autoclaved for 15 minutes at
125 degrees Celsius. The third sample had been autoclaved for 30 minutes at 125 degrees
Celsius. And the fourth sample was oven dried for 30 minutes at 125 degrees Celsius as well.
And you can clearly tell here that the color of the two autoclaved samples changed as we
autoclaved them, whereas the oven dried soybean meal did not change in color. And this is
illustrated also in the numbers that are shown here for the L* value, which gives an indication
of the lightness of the product. And as you would expect, the more we heat these samples,
the lower is the L* value for the products going down from 76.7 to 61.7 and 52.5 for
the soybean meal that was autoclaved for 30 minutes at 125 degrees Celsius. However, the
oven dried soybean meal did not change in L* value, and that indicates that this sample
was not heat damaged. When we look at a*, which is the measure of the redness of the
colors, we can see the a* went up from 3.4 to 10.0 and 12.5% in the two autoclaved samples
as they got heat damage, whereas the oven dried sample did not change in a* value. So
again, we clearly see here that two of the samples that were autoclaved, they changed
in color as they were heat damaged. We fed all four of these soybean meals to growing
pigs, and we determined the digestibility of amino acids in these samples. And this shows the effect of autoclaving time
on the apparent ileal digestibility and the standardized ileal digestibility of lysine.
And we can clearly see here that when we autoclaved the samples for 15 minutes or for 30 minutes,
we reduced both the apparent ileal digestibility and the standardized ileal digestibility of
lysine. And the standardized ileal digestibility went down from 93% to 84.2%. When we take a look at the concentration of
lysine and crude protein in these four samples of soybean meal, we see that the concentration
of crude protein did not change as we heat treated these soybean meals. So crude protein
stays constant. However, the concentration of lysine was reduced from 3.05 to 2.83 and
2.69% as we autoclaved the samples. Whereas the oven dried soybean meal had the same concentration
of lysine as the control sample, indicating that the oven dried sample was not heat damaged.
And we saw before that as we autoclaved the soybean meal samples, we reduced the digestibility
of lysine in these samples. And now we see here that we also reduced the total concentration
of lysine in the samples. And that fits with our hypothesis that heat treatment and heat
damage will reduce the digestibility of lysine and the total concentration of lysine at the
same time. We can get an estimate of this heat damage by calculating the lysine:crude
protein ratio. And then express lysine as a percentage of crude protein. And we can
see here that in the control soybean meal, the lysine:crude protein ratio is 6.29%, whereas
in the two autoclaved samples, it’s only 5.75 and 5.57%. So, this shows also that the two
autoclaved samples were heat damaged because the lysine:crude protein ratio goes down.
In contrast, the oven dried sample had a lysine:crude protein ratio that was not different from
the control. So what this indicates is that if we analyze our feed ingredients for both
crude protein and lysine, then we can calculate the lysine:crude protein ratio. And if we
know what that ratio is for the undamaged or the control ingredient, we know what it
should be, then we can look at each delivered ingredient and determine if that ingredient
was heat damaged. The control, or the undamaged, ingredient will have a different lysine:crude
protein ratio for each ingredient. So that is something that is unique for each ingredient.
But once we have established that, we can actually look at each delivered ingredient
and determine what the degree of heat damage in this ingredient is. So again, calculaitng
lysine:crude protein ratio helps us estimate the quality of the protein in the ingredients. So this concludes the first part of our presentation
on methodologies to evaluate feed ingredients. And the second part will be available shortly,
and in the second part, we will discuss what happens to the nutrients that are present
in the feed ingredients after the pig has ingested the feed. So with that, I would like
to thank you for your attention, and if you are interested in more information, please
visit our website at nutrition.ansci.illinois.edu. Thank you very much.

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  1. Mr Hans sir, Your have explained it really well. I need your support on understanding little bit more on feed nutrition for broiler. Please let me know how can I contact you. Please mail me on [email protected]

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