Carbohydrates and energy. Important for growth, important for
gain, important for lack.
We need to understand how some of those
requirements
and the content of the feed is calculated
so that we can better understand how to
formulate the right ration for the right set
of animals.
We'll get into into that today on diving
in today diets. I'm Brad White. Joined today
by doctor. Philip Lancaster and nutrition here. It's
Beef Cattle Institute. Good morning, Philip. Keep going,
Brad. So happy to have you with us,
and this is a a great time to
Kinda get into the details, almost said diving
into the details.
Excited about our title here, but get into
the details of,
things like carbohydrates
and energy and understanding
both how cattle use them and how some
of those requirements and contents are calculated,
And I may have you start out by
just giving us some background on the basics
of,
what do we use carbohydrates
for? What are cattle use carbohydrates for?
So the the main thing and really the
only this energy. So carbs
provide the bulk of the energy in beef
cattle diet.
So there... There's lots of different forms of
carbs that beef cattle used, but that's what
they didn't and they provide energy. Not only
for the animal, but they provide energy for
the microbes in the room.
And so that's that's the main thing that
we're concerned about with carbs.
So when we think about making sure that
they have enough, that energy requirement,
varies quite a bit by both stage of
production and age. Right? When when are some
of the maybe high need times versus low
need times?
So the energy requirement varies through the production
cycle of a cow,
where
when she is in early lac, those first...
3 to 4 months after calvin. That's her
highest energy demand,
our highest energy requirement of the whole production
system.
The lowest
energy time is after she leans that calf.
She's in mid gestation for the next 2
to 3 months.
And the fe is
hasn't really ramped up its growth, a whole
lot yet, and so that's her lowest energy.
Environment of the production cycle.
And then as she gets into late gestation,
and that would be kind of the the
in between where that fetal growth is ramping
up and so her energy requirements are increasing,
but they're not as high as they are
during early lac plantation. Given those changes,
when we think about how we're measuring
energy, which is really what we're talking about.
1 of the most common ways that that's
described is through the net energy system. So
what maybe define the net energy system and
tell me how that net energy is calculated.
So the net energy system was
designed to to take us all the way
down from... The gross
energy in a feed or the to
the
energy in a feed that
is
goes to different functions in the animal. So
let's let's walk through it and let's break
it down. So we start with the gross
energy and the feed. That's the total amount
of energy in a feed,
but it tells us nothing about how much
energy the animal is going to get out
of the that feed. And so the next
step or the first step really
is to go from gross, energy in the
feed to that digestible
energy from the feed. And so what we
lose there is the fecal energy, So if
you take gross energy minus the energy that's
in the feces, you get the digestible energy
that is provided by that you feed.
And digestible energy is the biggest part of
the energy that an animal gets out of
that feeds. So fecal energy is generally the
largest loss of energy
from a feed stuff. And so why does
it go through to the feces why doesn't
why don't they digest more of it? Is
it something functional about that type of
energy? No, it's it's... It's something functional about
the type of carbohydrates
that are in that feed stuff. So
let's
take for instance, forage,
We talk about a Td in value or
a digest ability of forge being somewhere around
60 percent. Well, that means 40 percent is
coming out in the feces. So that's a
really big energy loss as a proportion of
the total.
Things like corn grain.
They have a digestive... It has a digest
ability of around 88
percent,
and so
then that means only 12 percent is coming
out in the feces.
And so
we...
Put a lot of emphasis on digestible energy
because it's the biggest
energy
loss or or right there.
And so another term that you probably are
more familiar with is Td in or total
digestible nutrients. And, that is roughly equivalent to
digestible energy. And so lots of times when
we're formulating diets for beef cows. We are...
Talking about Td, not digestible energy. So you...
You're... The 3 terms that we're using Td,
digestible energy and net energy are close to
synonyms or they are synonyms.
No. So digestible energy and Td in are
close to synonyms.
Net energy is no... Not a s for
digestible energy. So the next step... From digestible
energy is the animal has to do something
with those carbs
that it digested and absorbed. And so
We go from digestible energy to what we
call the the amount of energy that's metabolized.
So metabolized
energy of a feed.
And the difference between those is the amount
of energy that is lost to methane.
Which is a little bit weird is how
they use it because really that's lost during
the digestion process, but that's where that
calculation comes in.
And then the amount that is lost in
urine. So it was... That energy was... So
those carbs.
That those,
actually, it's part of the proteins go into
energy 2. And so the amount of nitrogen
that is treated in urine. It's not completely
ox
or metabolized, so that's a loss of energy
from the total
amount of gross energy that was in that
feed. So that's how we go down to
tab.
And then from
energy, then we go to net energy. And
so the difference between metabolized
energy and net energy is the the amount
of heat that's produced during metabolism
of those carbs.
And so
net energy then has
several different
functions. So if I take if I think
about a feed stuff,
a feed stuff has 1 gross energy value.
It has
1 digestible energy value.
For an animal or a for a a
beef or a cat rum. It has 1
metabolized
energy value but it may have multiple net
energy values because it may have a net
energy for maintenance value, and net energy for
gain value
a net energy for lac location value.
And so it will have several net energy
values depending on how that energy is being
used by the animal. So however, that metabolize
energy is being used,
that trans
formation from metabolized
energy to net energy is different.
So maintenance and lac plantation,
use net energy or use the metabolized
energy more efficiently.
So a feed stuff will have a higher
net energy for maintenance value or a higher
net energy for lifetime value, then it will
a net energy for growth value because that
transformation of
energy to net energy for growth, basically the
growth of muscle and fat,
is lower that that efficiency is lower than
it is if I... If the animal is
using that metabolism energy for maintenance
or lac relaxation.
Okay. So now now you've let me to
several questions. Yeah. Let me make sure I'm
on the right track here. So my...
Total energy in the diet, I really don't
care about. The Td
is what I do care about or the
metabolized energy. Mh. But then
after that step, there are some more losses
before I get to what the animal can
use, and that's where the net energy calculation
comes into play. Yes. Right. And so my
net energy, if I just think of it
simply as, if I have... Let's say I
have a growing calf, and we'll leave lac
plantation out for a second. I've got a
growing calf.
He has to fulfill his net energy for
maintenance requirement every day to maintain his body
weight.
Anything
above and beyond that is net energy for
gain. Right? Yes. So my feed will have
both
M, net energy maintenance and G, net energy
gain listed on it. But the
G number as you're saying is often
smaller, even though it's the same feed stuff.
So I'm struggling to understand. Yeah. Why wouldn't
it just be the same energy because it's
really about how the animal is using the
metabolism
energy. So the conversion from
energy
to net energy for maintenance has an efficiency
of around 0.7.
Alright? So only 30 percent of it goes
to heat production and 70 percent of it
is used to to maintain the animal. The
conversion from metabolized
energy to body tissues, so muscle and fat
has a efficiency of about 0.4.
And so
that means that when I take metabolized energy
times 0.4. I get a much lower number
than when I take metabolized energy times point
set... It. So why why is it that
much so sufficient for gain? What's the basis
behind that? Because of what what we think
and we understand is because of the process,
a coupled different things. The process of s
sizing new molecules,
alright, to grow tissue
requires more
Atp and so you get more heat production
because you're s synthesized new molecules.
And
so proteins in the body are constantly turning
over, even muscle proteins.
And so you've got some
proteins that are being broken down, and then
they gotta be rebuilt, so there's an
inefficiency
there
because proteins that were already built have be
rebuilt
as as that protein turnover happens. And so
there's an there's a... That decreases the efficiency
then of metabolize
energy being used for,
muscle and fat growth. K? So,
I have to understand the differences between those,
and there's also
the net energy for lac relaxation, which obviously
applies to lac cows. Which similar to growth
as less efficiency because we're making new stuff,
basically what you're studying. But but yes, it
does, but not nearly as much. Which
because there's no there's there's no turnover
of
stuff in milk.
It's made once, and it leads.
And so the efficiency of metabolize energy lac
relaxation is is very close to the efficiency
for maintenance. So it's... In fact, the dairy
industry just uses 1 number. They they use
1 number for net energy because those 2
users. So close that it doesn't make that
big a difference when it comes to formulating
die. K. So when I'm using those for
making a irrational, and I'm gonna make a
ration for growing calves,
I have... And and just for example, Let's
say I've got a pound of feed,
and it has a net energy value
of something, and then it has a net
energy gain of something. So would that be,
like, 1 and 0.4
0.9 and 0.4 or something like that? Yeah.
So let's... So
depends we're gonna we're gonna focus on,
mega cows per pound. Alright?
And so you're you're gonna be somewhere... Your
energy for maintenance is gonna be somewhere
around,
you know, 0.7
to 1, somewhere in that ballpark,
and your net for gain is gonna be
somewhere
in around 0.3 to 0.6.
Okay. So so let's say I've got that
feed, and it's 0.7 and 0.3, for example.
Then...
Do do I get both of those out
of that same pound of feed? So can
I use a pound to feed and and
I can say, okay, I'm getting 0.7 from?
Net energy maintenance and I'm getting 0.3 from
gain or do I have to use them
sequentially. I gotta do maintenance before I can
do gain. We...
Technically,
the animals using everything all at the same
time. Right. But mathematically and for our brains
to to handle it, we do it sequentially.
So what we do is we we calculate
the net energy for maintenance requirement.
Of an animal.
And then we use that 0.7 number
to figure out how many pounds of feet
is gonna require or to meet that net
energy for maintenance requirement. And then we've got...
Well, then we've got... So let's say, the
animal is eating
20 pounds of feet. Okay? And so let's
say it took
8 pounds of feed to meet the maintenance
requirement. That means I've got 12 pounds of
feed left
suit that can be used for gain. And
so then I take that 12 pounds since
times the net energy for gain number, the
0.3,
that tells me how many mega calories
of energy are available for gain on it
per day.
And then I can use some other equations
to estimate what the rate of gain would
be for that animal based on having 12
mega cows of net energy for gain available.
Because I can't I can't get the gain
unless I do maintenance first. And and, yes,
they're using them both at the same time.
The analogy that I've used before and you
can tell me if this... Makes sense or
not. Is it it if you had a
pitcher, like a drinking pitcher and you put
a small glass inside of it,
until you... If that glass represents maintenance
until I fill up the glass,
I I don't have any water in my
pitcher, which is gained. And I always have
to fill up the glass first. Is that
is that a reasonable analogy So you you
gotta you you pour the water into the
glass Yep. And then when the glass starts
to overflow, then you have some water that
starts to fill up the rest of the
picture. And, yes. That's of that's a pretty
good analogy that we gotta fill up the
maintenance
glass first
before we can have anything flow over
into the game to get your. And it
doesn't matter if your feed says it's got
a high E g value.
You never use it unless you fill up
that maintenance glass. First. Yep. Exactly. So I
think that that helps me make sense. The
the problem is I I have a grasp
on that Net energy system But then if
I send feed to the lab, when I
get it back, it has things like India,
Td d in.
Ad d f, may even have other... It's
a alphabet soup of... You may... I mean,
you may also have AANDF0DF,
So I appreciate that the nutrition are working
with other professionals on really up in their
acronym game. Right? Really going making everything in
acronyms, so nobody can understand it. We're almost
as good as the government. Yeah. Almost as
good. So help me sort this out,
Td. Let's start with Td d, Ad f
and Nd, What are they? And what do
they mean relative, and and especially, relating back
to Net energy for me. Okay. So Td,
we talked about a little bit about, Td
is total digestible nutrient. So it's the amount
of
carbs
plus protein plus fat
that are
digested. I'm okay. So you add them all
So if I got, you know,
part... My feet is
70 percent carbs and those carbs are 60
percent digested, and then I take that number,
and I've got feed that's 15 percent protein
that is 70 percent digested and I... So
that's how I get that total digestible nutrients.
And that is, like I said, roughly equal
to digestible energy in the net energy system.
In the f is neutral detergent fiber, and
this is a number that's
I say relatively unique to rum
in the fact that,
the old feed analysis system used to use
crude fiber.
And that value was
very
to rum nutrition because it doesn't tell you
much of anything about how much actual fiber
is in there. It works for mono gas,
but not very well for room it's. And
so
the neutral detergent fiber is an estimate of
the total fiber
in a feed stuff. So it's the cellulose,
the hem cellulose and the l.
And and gives me an idea of everything
all the fiber or plant cell wall that's
there.
The Ad
is the acid detergent fiber. And the acid
detergent fiber is a a little bit different
analysis,
it breaks down the hem cellulose. So what
I'm left with is the cellulose and the
Malignant.
And the difference between those 2 numbers
is
the Nd mdf number tells me the total
amount of fiber and it tells me kinda
how bulky that feed is gonna be. It's
gonna... It's it's somewhat related to intake. How
especially on forage.
How much is that Animal gonna be able
to eat because that
feed is gonna be really bulky and how
much room is gonna take up in her
in the room.
The Ad f value is gonna be somewhat
related to
the Td.
Alright? Because
I took out the most digestible part of
the fiber, which is the hem cellulose, and
the ad, is the cellulose and ligand, which
are the 2 least digestible parts of the
fiber.
So when we talk about forage
an Ad f value that's higher means lower
digest ability. And so most labs
use that Ad value
to estimate the Td. There are some equations
that have been developed
to
relate those 2 things. There are some other
equations that use
Ad f, plus Nd, plus crude protein,
but most labs use
equation that is just based on Ad f.
Because lab don't
The only way to truly get Td in
is to feed the
feed to an animal, and that's not practical.
From a wet lab perspective. And so we
have these equations then that can convert
Ad
to Td d in And the question from
a from a practical standpoint is knowing
what equation they're using and how well that
equation works for your type of forage
because there are some based on alfalfa, there
are some based on grasses and and they're
different
and they they don't necessarily cross over well.
So how do I relate any or all
3 of those to my net energy? Okay.
So good question. So that we said the
Td in is pretty much equivalent to the
digestible energy. So then I can take there's
in the in the beef cattle Rc nrc,
there are...
Couple of equations where I can take Td
in and I can convert that to net
energy. And then lots of times, a feed
lab will do that for you, and they'll
report a Td end and net energy values
on the feed report. Sometimes they don't. But
you can get those equations for from the
Nrc, and you can convert that to,
NEM and E g. To a couple...
And that helps because that's what we've talked
about as far as formulating my ration a
couple other things that we talked about may
show up were a India. And o m
Nd f. What it what do those mean?
So those are adjustments that we've made over
the years to the Nd
procedure.
So the original Nd procedure
just had
the
neutral buffer in there to break down the
cell si, and then what you're left with
was the plant cell wall. Well, different feed
stuff that have
some things that can
hinder that process. So feeds that have a
lot of starch, starch tends to clog up
the filter,
that we use to filter out the cell
valuables. And so then what you end up
with as an inflated number of plant cell
wall because, not all the cell soluble will
go through the filter. So the a in
a and d f means that they have
added alpha amy
to the procedure,
to break down the starch and let it
filter through, and then you can get a
more accurate estimate of the Nd mdf. The...
O m,
part of Nd f is stands for organic
matter. So now what we're doing is we're
we're adjusting Nd mdf as a proportion of
the organic matter not of the total feed.
So we take the
ash out.
And now we look at Nd mdf as
a proportion of the total organic matter instead
of as a proportion of the total diet.
And so when you got some feeds that
have a high ash content,
that can make a pretty big difference.
Excellent. So this... If I send a sample
to the lab, I'm gonna get these type
of values back.
If I'm purchasing a feed
and I look at the feed tag, what...
Which value should I look at to figure
out what my net energy is.
None. Nothing and that is the that is
the biggest
limitation of
manufactured feeds is a feed tag does not
require any kind of
energy value to be reported there. So you
have no way of estimating
the energy value of a
commercial fee. Yeah. But but there's there's no
there's no Td in. There's there's no nothing
reported on the tag. It was it's not
required as...
Part of law,
and so you that you just don't have
anything. So the only thing you can... 2
options. You can call the feed
sure, and they may have something from their
formulation that they might be willing to share,
or you have to send in a sample
of that feed to a lad where they
will do a nut nutrient analysis and give
you an estimate of Td in that you
can then work with. Which which there may
be times that it depends on how much
of that feed I'm feeding and why I'm
feeding it, but there may be times that
that's important. There may be times that's not
as important because I'm feeding it for another
reason. Yeah. So Yeah. Feed tags labeling laws
were designed to,
protect the consumer from fraudulent,
Feed manufacturing, not designed for nutritionists to be
able to form to be ration with those
feeds. Yeah. Absolutely. Great information on energy today,
Philip up. I appreciate you sharing with us.
We walk through the net energy system. We
talked about what we would do with our
feed analysis.
Appreciate you sharing that info. Thanks, Philip. Yep.
Thank you.