This course will explore the concepts driving current food production science (population growth, urbanization, emerging affluence, resource constraints, and underlying biological limits) with the main focus on livestock production. Each of the major food animal species (dairy, swine, beef, and poultry) will be covered in terms of their universal life cycles, constraints to production and emerging societal issues. Throughout the course, we will tackle some difficult and important questions: What are the major health benefits and potential concerns regarding the production and consumption of animal products? How does animal production affect the efficient use of resources and impact our environment? Can cost of production be reduced to meet growing demand for animal products around the globe while maintaining health and safety for both animals and consumers? What are the different types of animal food production systems? Myths and misconceptions surrounding the animal food systems will be discussed. We’ll also look closely at some of the global issues, problems, and challenges in these food systems which scientists, farmers, and veterinarians, are attempting to solve through collaboration. Lectures will be delivered by several experts from the University of Pennsylvania, School of Veterinary Medicine who are intimately involved in the study and advancement of animal production systems. The course is geared towards learners who seek a greater understanding of animal food systems as well as those who might have never visited an animal farm, but have a desire to learn more about where some of our food comes from and issues surrounding sustainability.
What are Roughages?
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Из курса от партнера University of Pennsylvania
Feeding the World
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Animal Feeds and the Environment
This module focuses on animal feeds and their important role in the animal production system. You will gain an understanding of the constituents in feed as well as how feed is classified. We will also examine and explain how nutrients flow through the environment. Finally, we will look at the problem of food waste and identify solutions.
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Dr. David GalliganProfessor of Animal Health Economics
School of Veterinary Medicine
James FergusonProfessor of Nutrition
School of Veterinary Medicine
So what are roughages in animal diets?
Well, first of all roughages are defined as crude fiber greater than 18%, but
the crude protein can vary anywhere from 5 to 25%.
These are important in herbivore diets.
They're bulky, they have a low weight to volume, and
they can be from pastures, hays, or silages.
And within that, we have hays, we have straws, we have fodder,
which would be a residue after processing removing the grain.
We also have corn cobs.
After you shell the kernels of corn, we can feed the hobs, the cobs, excuse me.
Or we have halls, like peanut halls.
After you shell the peanuts,
we have the residue that can become a roughage source for animal diets.
So the types.
NRC classifies these as fresh roughages, like pasture or green chop.
Green chop would be material that we cut every day, and
then feed it to the animals.
We offer it to them within the barn or a wilted forage, where we'll cut it,
and let it sit for about 12 hours to let some of the water come out of it, and
then feed that to the animals.
Hay, you're probably all familiar with,
which is a dry product created in 80% dry matter.
And hays can be either from a legume or a grass.
And then silages usually, these are roughages that are stored wet,
anywhere from 30 to 50% dry matter.
They're fermented for storage, so they can be preserved for a long time.
And silages can be made from grasses.
They can be made from legumes.
They also can be made from grain/forage mixes, things like corn silage, or
wheat silage, or oat silage or barley, barley silage.
And then we have straw and fodder.
After we pick the grain and use that for human use, the plant residue,
like straw or the fodder that remains, can become an animal feed.
And so, again, we have the whole plant.
And we can cut that into silage in an early stage of maturity.
At full maturity, we'll pick the ears and shell the grain.
And then we can have that as shell corn, or
we can grind up the whole ear of corn and have that as ear corn.
And the residue then can become an animal feed, corn fodder, which is the residue
after combining to get the ears, or corn stover, which would include the leaves and
stalk, the leaf, the husk, and the entire material after getting the shell corn.
And so we have both, the whole plant can be fed,
or we can feed the residue after picking the grain.
Just looking here, in this slide, what is the difference?
And so we really have two types of corn.
We have corn that you'll see in the field that's grown for grain, primarily have
large ears relative to the stock, or we have corn that is grown for silage.
Probably 90% of the corn grown in the United States is grown for grain.
However, we look at the whole plant, the whole silage, we see that whether its for
grain or for silage, it has a similar crude protein content,
a similar fiber content, NDF, or plant cell wall, and
a similar digestibility IVNDF is the in vitro NDF digestibility.
When we look at the grain, what proportion of those plants are grain?
Grain corn has a little bit higher proportion of the plant as grain,
43.7%, versus silage, which is about 41%, but, again,
similar content of crude protein fiber and digestibility.
And then as we get into the husk, the shank, the stalk of the plant, the stalk,
the leaves, the cob, you can see they have very similar nutrient contents.
So the main difference between a corn plant that's grown for grain versus silage
is the relative proportion of the ear to the rest of the stalk.
The nutrient content is very similar.
The critical component of forage is when we harvest it.
When the animal grazes, we have the energy cost of the animal grazing that forage,
and we have some dry matter loss,
because they're not that efficient at consuming all the dry matter in a field.
But we like to turn animals in to harvest pasture when it has
an optimal nutrient content.
And oftentimes that would be in grasses
when it's about 10 inches to 15 inches in height.
As it gets higher than 15 inches, actually the nutrient content is getting lower,
because it's getting more mature.
Similarly, when we harvest forages, we can do it when they're wet, or
when they're wilted, or when they're dry.
What we see on this slide, that if we harvest it when it's very wet,
we have high losses from storage.
It's too wet, we get a lot of seepage.
As we let the material dry, we get less losses from
storage losses, seepage, but we get more field losses.
As material gets dried to make hay, we may get what is called leaf shatter,
that the leaves get dry when you go to make it into hay.
You end up with some of those leaves getting broken and lost in the field.
And so what we'd like to do is actually harvest it somewhere there in the middle,
where we have minimal storage losses, minimal field losses, and
that would be for making silage.
So the roughage nutritional quality varies.
First of all, we have types, grass versus legumes.
Secondly, maturity at harvest.
One of the great attentions farmers have is that as they let grasses get more
mature, or legumes, yield increases, but nutrient quality decreases.
And so there's an optimal yield digestibility at which they should
harvest that plant.
And what makes the nutrient content decrease is
lignin increases as the plant matures.
That give the plant rigidity, so it can stand up, but
it also lowers the digestibility.
And so, if we look here at comparisons of grasses versus legumes,
versus corn silage, the important point is that legumes are high in protein, 19.8%,
grasses are about 10.2%, corn silage is about 7.7.
The NDF content, the fiber, legumes are about 40%, grass is about 58%,
notice higher fiber in grass, and corn silage is about 42%.
Starch content is low in legumes, 2.9%, it's low in grasses, 2.1%,
and it's high in corn silage, because it contains the ears of corn, 31.5%.
Notice that legumes have high calcium, 1.48%,
versus calcium in grasses of 0.61%, and calcium in corn silage of 0.24%.
So the main difference in a legume versus a grass, high protein content in legumes,
high calcium content in legumes, lower protein content in grass,
higher fiber content in grass, and lower calcium.
Whereas corn silage, it's a grass, but
because it contains ears of corn, it has a higher starch content.
So let's consider hay a little bit, the dry forage.
Many different ways to store hay, in stacks or bales.
Again, the key critical thing with hay is the major factors that affect its quality
is the moisture content.
We have to let the hay dry.
Or if it's too wet,
if it's greater than 20% moisture when we make those bales of hay, it will mold.
And also, worse, it can heat and also burn.
And so it has to be under 20% moisture or over 80% dry matter.
Then the stage of maturity has a major affected baling.
And we see on this slide that as we get more mature, we increase dry matter yield
up on the right, but the nutrient content is diminishing.
And what we'd like to do is maximize yield and maximize nutrient content.
And then, we see on the bottom right that legumes tend to have
a higher digestibility than grasses, and that influences the quality.
And this looks at just what are we talking about.
So, here's an alfalfa plant.
In the middle, we see we have buds and flowers.
On the upper left, we see a full alfalfa flower.
Up on the upper right, we have alfalfa that's just reaching a bud stage.
And that would have the highest protein, the lowest fiber.
And then in the middle on the right, we see it's just coming into 10% bloom.
And so fiber is increased a little bit, protein is decreased a little bit, but
yields will be slightly higher.
And on the bottom right, we have an alfalfa field that's gone into full bloom.
We want to harvest the alfalfa material when it's just in bud or
just at 10% bloom to maximize yield and quality.
Drying the forage in a field, if drying is not complicated by weather, if it doesn't
rain while you're doing it, there's little effect on the nutrient content.
And it's similar to having it fed as fresh forage.
Silage is produced by controlled fermentation of high moisture herbage.
The feed needs to be wet, usually about 35% dry matter,
although it can range from 25 to 50%.
You need to exclude oxygen,
and you need to have a supply of fermentable carbohydrate,
usually sugars that are present in the plant when you put it in the silo.
And lactic acid is produced to stabilize the material by dropping the pH.
The chemical changes, first when you put silage in, it heats for
the first two days.
If it's too dry, this is a dangerous time, because it can catch on fire.
And also this is a time when that heating can also damage protein and
make it indigestible.
After two days, the oxygen is used up.
The plant cells begin to die.
They quit respiring.
Anaerobic bacteria kick in.
They begin to produce acetic acid, dropping the pH.
Eventually, as the pH drops, those bacteria die.
Lactic acid bacteria take over.
And when we get down to a pH under five, usually, those bacteria die, and
we have about 7 to 8% lactic acid levels, a low pH, below 5, and
that product is stable for years.
It usually takes about three weeks for this to happen.
That product is stable as long as we cover it and
keep it protected during this time in storage.
And this looks at an overview of the process.
The material needs be chopped into a certain particle size so it packs well.
It needs to be then packed, so it's packed tight to exclude as much oxygen as
possible, covered, preserved, and then when it's fed out,
it needs to be done to keep the phase of the silo very vertical, so
we don't have a lot of secondary spoilage.
Bad silage too wet or
too little sugars, we have growth of Clostridia and botulism toxins can grow.
The pH stays about 5.5, and that can kill animals.
And then production of amines from some of the protein breakdown can create
biogenic amines that are undesirable odors, and
also have negative affects on animal performance.
Butyric acid can happen from Clostridia fermentation, and
it'll have a bad odor, and animals will not want to eat it.
And the pH characteristic on these bad silages is a pH that's above 5 that they
did not preserve well.
However, if we put it in too dry, it doesn't pack well,
there's too much oxygen, excessive heating, molds can grow, and
we have problems with toxin production.
So there's an art to making silage and preserving feed in this forage material.
When it's fed out, it needs to be kept vertical to protect the face to keep it
fresh to prevent excessive spoilage and
excessive oxygen from penetrating into the face of the trench.
And, usually, we need to remove about 6 to 12 inches a day, so
that the material stays fresh for feeding.
And when that's done poorly, there's problems.
Here we see in the upper left, a silage trench that has not been managed well.
The face is very irregular.
And over on the bottom right,
we see hunks of mold that's been produced in the silage, which are unacceptable for
animal feed, and they should be removed prior to feeding
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