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COLLECTION: GOAT HANDBOOK
ORIGIN: United States
DATE INCLUDED: June 1992
Extension Goat Handbook
This material was contributed from
collections at the National Agricultural Library.
However, users should direct all inquires about the
contents to authors or originating agencies.
DOCN 000000022
NO C-1
NUTRIENT REQUIREMENTS AND FEED VALUES
R. S. Adams; Pennsylvania State U., University Park
B. Harris; U. of Florida, Gainesville M. F. Hutjens;
U. of Illinois, Urbana E. T. Oleskie F. A. Wright;
Rutgers U., New Brunswick, NJ
D. L. Ace; Pennsylvania State U., University Park
Nutrition
1 The Ruminant Stomach The dairy goat belongs to the
cud-chewing or ruminant group of animals. This group,
which includes cows, sheep, and deer, has the unique
ability of being able to digest roughages which contain
relatively large amounts of cellulose. Cellulose is
a part of plants and thus one of the largest potential
sources of energy for animals. The digestive system
of ruminants can also manufacture many essential nutrients.
Drawings of the four compartmentalized stomachs of
the ruminant are shown in Figure 1, indicating the
changes from youth to maturity.
2 Rumen -- This is the largest of
the four compartments representing about 80 percent
of the total stomach area. The rumen is often called
a fermentation vat because it contains a large number
of microorganisms bacteria and protozoa, which supply
enzymes that break down fiber and other parts of the
feed. The cellulose is converted to volatile fatty
acids that are absorbed through the rumen wall and
provide up to 75 percent of the total energy needs
of the animal. Protein is produced by the microorganisms
from the nitrogen in the feed. The microorganisms
also manufacture all the B vitamins along with Vitamin
K.
3 A unique feature of the rumen is
that it is located in the beginning of the digestive
system. This position makes it possible for the host
animal to take advantage of all the nutrients produced
by the microorganisms as well as the organisms themselves
further on down in the digestive tract.
4 Reticulum -- This is the second
stomach, sometimes called the ''honeycomb'' due to
the structure of its wall and is located just below
the entrance of the esophagus into the stomach. Act
ually the reticulum is a part of the rumen, separated
only by a partial wall.
5 Omasum -- This portion of the stomach
is shaped like a small cabbage. It consists of hanging
layers of tissue similar to the curtains on a stage.
The relatively large surface area of these folds permits
absorption of moisture from the feed as it passes
through to the fourth compartment.
6 Abomasum -- This part is more often
considered the true stomach. It functions just like
that of the simple-stomached animals. It contains
hydrochloric acid and enzymes that break down feed
materials into simple compounds that can be absorbed
by the stomach wall and the intestines.
7 Food from the mouth passes through
the esophagus and enters the rumen, where it is mixed
with ruminal contents and fermented and degraded by
ruminal microorganisms. Some of the feed is regurgitated
for more mastication (chewing the cud) and then returned
to the rumen for additional fermentation. Fatty acids
resulting from fermentation of the feed are absorbed
into the blood stream from the rumen and reticulum.
The remainder of the feed passes through the omasum
and abomasum where further digestive action takes
place. As feed ingesta enter the small intestine,
enzymes further break it down and the released nutrients
are absorbed into the blood stream for use by the
goat. The ruminant animal is unique in that fibrous
feeds can be utilized with the help of ruminal microorganisms.
Also, all amino acids can be synthesized by the microorganisms
from plant proteins as well as all the required B-vitamins
and vitamin K.
8 Primary Feed Nutrients Generally,
feed nutrients are divided into six groups. Following
is a brief discussion of these nutrients:
9 Protein -- Protein is the only
nutrient that contains nitrogen. Protein quality -
a term referring to the amino acid content - has no
significance in ruminant nutrition, except at exceptionally
high levels of milk production. Rumen microorganisms
manufacture their own body protein, consisting of
all the necessary amino acids, which are later digested
by the host animal.
10 Protein makes up the basic animal
tissue of the body and is vital for growth, milk production,
disease resistance, reproduction, and general maintenance.
The body has very little if any excess protein. Mostly,
the nitrogen is eliminated by the kidneys and the
rest is burned as energy. Since protein is generally
the most expensive part of the ration, it is costly
to feed more than what is needed. Protein requirements
vary between 12 and 16 percent of the ration dry matter
with the latter needed for high milk production.
11 Urea and other nonprotein nitrogen
products can be utilized by the microorganisms of
the rumen for the production of protein. They are
not generally recommended for goats because they are
very selective in their diets.
12 Energy -- One of the first limiting
factors of milk production is a shortage of energy.
This short age is most likely to occur at the very
early stages of lactation. Most of the goat's energy
comes from the breakdown of the fiber of forages,
while the remainder comes from the burning up of concentrate
starches and fats.
13 Energy is measured in two different
ways by the feed industry. The first and more established
method is by Total Digestible Nutrients (TDN). As
the name suggests, the TDN consists of the sum of
the digestible carbohydrates, digestible protein,
and digestible fats (multiplied by 2.25 since fats
contain that much more energy than protein or carbohydrates).
The TDN system takes into consideration only one nutrient
loss - feces. For this reason, the net energy system
is gaining in popularity. This system considers energy
that is lost in the feces, urine, gases, and the work
of digestion. In recent years this system has been
even more refined to account for varying energy utilization
needs for body maintenance, weight gain, or milk production.
14 Minerals -- Many minerals are
required by the goat. Most can be obtained from good
forage and a regular concentrate mixture. The major
minerals of concern are calcium, phosphorus, and salt,
which are usually added to the ration either in the
grain mix or by free-choice feeding. Goats do not
consume minerals free choice according to their needs.
It is, therefore, recommended that minerals be force-fed
through the grain mixture or mixed with a succulent
feed like silage or greenchop, if possible. The ratio
of calcium to phosphorus is important and should be
kept around 2:1. If these minerals must be fed free-choice,
such as to dry goats and yearlings, a good mixture
is one containing equal parts of salt and dicalcium
phosphate, or a similar commercial mix.
15 Vitamins -- Vitamins are needed
by the body in small amounts. Since all the B vitamins
and vitamin K are produced in the rumen and vitamin
C is manufactured in the body tissues, the only vitamins
of concern in ruminant nutrition are vitamins A, D,
and E. During the late spring, summer, and early fall
the animals can get all they need from green pastures
and plenty of sunshine. In addition, they can store
a good supply of these vitamins to carry them into
the winter months. Nevertheless, it is a good idea
to add these vitamins at the rate of 6 million units
of vitamin A and 3 million units of vitamin D to each
ton of grain mix during the winter months as an added
precaution since they are not very expensive.
16 Fats -- Fats are of little importance
in the ruminant ration. Practically all feeds contain
small amounts of fat, and added levels are not practical.
A level of 1.5 - 2.5 percent in the grain mixture
is normal.
17 Water -- This is the least expensive
feed ingredient, yet a deficiency will affect milk
production more quickly than the lack of any other
nutrient. Water is not only the largest single constituent
of nearly all living plant and animal tissue, but
it also performs exceedingly important functions during
digestion, assimilation of nutrients, excretion of
waste products, control of body temperature, and the
production of milk. Ready access to water is important.
Goats with water constantly available have been shown
to produce more milk than those watered twice daily
and over 10 percent more than those watered only once
per day.
NUTRIENT REQUIREMENTS AND FEED VALUES
COLLECTION;GOAT HANDBOOK
ORIGIN;United States
DATE_INCLUDED;June 1992
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