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Generally, leaves are more nutritious than stems and new leaves more
valuable than old leaves. There are some exceptions to this
generalization, especially when certain plant chemicals, such as
tannins prevent proper digestion of the plant tissue. The total effect
of these binding chemicals on the nutritional values of plants are not
fully determined, especially in many of the browse plants.
5 The Goat and Diet Selection
Goats are agile and have exaggerated control of their mouth parts,
allowing them to be very selective for diet. They are able to stand on
their hind legs and climb rock cliffs and low growing trees to gain
access to relished plants and plant parts that are unavailable to other
livestock species. Goats have a mobile upper lip, effective in nipping
off plant parts very selectively. As a result, the goat's diet is very
diversified, consisting of small components of a large number of plant
species. Very simplified vegetation, an all-grass meadow, for example,
does not provide good nutrition for goats over a long period of time.
Goats need access to a wide variety of plants in order to exercise diet
selection, as different plants increase and decrease in nutritional
value with seasonal changes.
6 The Goat as a Brush Control Tool
Many of the browse species have invaded or become overabundant in
old, abandoned fields or on range and pasturelands following prolonged
grazing by other livestock species. These invading species,
collectively called ''brush'', often can be suppressed or eradicated
using goats. Goats are effective as brush control tools, when the
following requirements are met:
1. The brush is either low-growing or is reduced to low growth by
mechanical means,
2. The brush species is preferred by goats,
3. Goats can be concentrated in large numbers for a relatively
short period, then removed for an extended period.
7 Each time the goats are concentrated, they consume the leaves and
twigs of the brush species, as well as a substantial portion of the
grasses. When the goats are removed, the grasses recover more quickly
than the brush. After several sequential grazing and rest periods, the
brush is reduced to a density easily controllable, with a few goats
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GRASSES, FORBS AND BROWSE
included in the grazing herd. This method of brush control has proven
successful in several regions of the United States, as well as at many
locations around the world.
VIDF 79,80
úúúúúúúúúúúúúúúúúúúúThe National Dairy Database (1992)úúúúúúúúúúúúúúúúúúúú
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%f TITLE;GRASSES, FORBS AND BROWSE
%f COLLECTION;GOAT HANDBOOK
%f ORIGIN;United States
%f DATE_INCLUDED;June 1992
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HEAT STRESS
HEAT STRESS
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 000000054
NO F-11
TI HEAT STRESS
AU J. D. Roussel; Louisiana State U., Baton Rouge
RV L. J. Hutchinson; Pennsylvania State U., University Park
DE Anatomy and Physiology
Text
1 Nearly every life form is affected in some way by high
temperatures, and goats are no exception. It is not heat alone that
causes stress to the goat; but it is the combination of temperature and
humidity when some crucial limit has been reached, which shuts down
all bodily functions other than those critical for survival.
2 Water and Feed Intake
The most immediate impact of heat stress can be seen in changes of
water and feed comsumption. As the temperature rises, so does the
animal's need for water. Plenty of water should be provided,
free-choice, at all times. However, if water becomes scarce, goats hold
an advantage over other domestic non-desert species in that they are
better adapted to utilize the water content of feeds. However, rising
temperatures also tend to reduce voluntary feed intake. This is the
result of an attempt by the animal to reduce the production of body
heat especially from fibrous feeds, lower physical activity, seek shade
and change grazing to night hours.
3 Nutrition and Reproduction
A long range result of diminished nutrition due to heat stress is a
reduced kid crop. If the doe is pregnant, especially near the end of
gestation, this heat induced lack of proper nutrition may result in
literal starvation of the fetus. On the other hand, if the doe is not
pregnant, an insufficient supply of energy due to heat stress will
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HEAT STRESS
cause absence of follicular development. The same is true for the buck
in terms of sperm production. Extremes in heat can affect reproduction
directly as well, through 1) sperm and ova degeneration within the
reproductive tract, 2) creation of hormone imbalances via action of the
hypothalamus, and 3) suppression of libido and the physical act of
mating.
4 Removal of Body Heat
In order to keep such drastic events from occur ring, three major
physical processes exist by which heat can be dissipated. They are:
1) convection
2) conduction, and
3) radiation cooling.
Convection cooling occurs when an air stream passes over the body either
by wind or b ++++MISSING DATA++++
5 Hair Coat
Fortunately, the goat has it's own line of defense when
environmental temperatures exceed body temperature. The first means of
protection is provided by the coat, both from it's color and physical
characteristics. The principle behind coat color involves the reflection
of sun rays. It has been documented that white coats provide maximum
protection against radiant heat and black coats give minimum
protection, with variations falling in between. Reflective protection
can be provided through physical characteristics of the coat as well.
Contrary to popular opinion, long hair which lies close to the body is
desirable. In this way, the coat acts as a mat to physically prevent
the sun rays from reaching the animal's body. In addition, long hair
serves as an insulator from the heat, providing an air buffer zone
between the outer environment and the animal's body.
6 Skin Color
The next line of protection is the skin. Color of the skin is
important, except this time darker colors are preferred. The function of
the darker skin is to absorb any ultraviolet light which may have
penetrated the coat, thereby preventing damage to tissue proteins.
Having an excess of skin has also been implicated as providing heat
relief. It is believed that this excess skin serves to increase the
surface area in relation to body size in order to enhance evaporation.
This has been the explanation used in order to account for the large,
floppy ears found on goats and other tropical animals. Horns have also
been suggested as providing benefit by providing an area where blood
can be cooled before reaching the brain. Certainly, the little
understood rete of goats is in this connection a unique anatomical
structure designed to keep the brain of goats cooler than the rest of
the body.
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