Agriculture Reference
In-Depth Information
development follows the general pattern of growth priori-
ties, generally in the order of nervous system, organs,
digestive system, bones, muscles, and adipose (fat) tissues.
The organs and tissues have priority for nutrients in that
order so bone deposition precedes muscle development,
and fat is deposited after bone and muscle growth is almost
completed.
Postnatal growth is marked by development of neural
coordination, digestive system development, and changes
in bone, muscles, and fat. Long bones have a progressive
ossifi cation and growth pattern. Muscles change in size
and form, with individual muscle fi ber cells having an
increase both in length and in sectional area (radially)
during muscle development. Adipose tissue cells that are
formed prenatally are infl uenced in postnatal growth by the
nutrition of the animal and the stage of growth. The number
of fat cells increases early in postnatal growth before
increases in the volume or size of each fat cell, which can
occur later, even after maturity.
Locations of body development are anterior to posterior
and ventral to dorsal. Fat (channel fat or kidney, pelvic,
and heart fat) deposition occurs around organs fi rst, fol-
lowed by intermuscular, subcutaneous, and intramuscular
(marbling). Growth and development rates are governed
by both genetic potentials and environmental factors, pri-
marily availability of nutrients and climatic conditions.
The composition of body parts is variable, with bone tissue
containing high levels of minerals, adipose tissue contain-
ing high amounts of lipid, and muscle tissues containing
high levels of moisture. Bone and muscle cells have about
the same protein composition.
PRE - WEANING PERFORMANCE
Weaning is defi ned as the time when animals are no longer
nursing from the doe. Weaning may occur when the doe
no longer will allow the kid goat to nurse, but more often,
it is at an earlier time because the producer will separate
kid goats from the breeding herd for management or mar-
keting purposes. High pre-weaning average daily gains
refl ect the genetic potential of the kid goat and the mother-
ing ability of the doe.
Heavier body weight and faster growth rate are among
the most important pre-weaning traits. Birth weight of
Boer kids ranges from 6.6 to 8.8 pounds (3-4 kg) with male
kid goats weighing about 1.1 pounds (0.5 kg) heavier than
female kid goats. The weight of kid goats at weaning
depends upon the age and methods of weaning, but it is
often 40-60 pounds (18-27 kg). The growth of kid goats
from birth until weaning is highly dependent upon the
availability of milk from the doe and the types and amounts
of feeds available when the young goat begins to eat solid
materials.
Some sources indicate that goats can be successfully
weaned and have desired growth when the kid goats reach
2.5 times their birth weight and are consuming at least 1
ounce (0.06 lb, 30 g) of solid feed each day. Successful
weaning can also be accomplished when kid goat weight
is 20 pounds (9 kg) or age is at least 8 weeks. If the goat
to be weaned is not old enough to have a digestive system
adapted to convert forage or grain feeds into the nutrients
needed for growth and development, early weaning will
result in higher mortality or slower growth rates. The
physiological and other stresses when the goat is weaned
are termed weaning shock. Male kid goats are more sus-
ceptible to weaning shock than females, and healthy kid
goats experience less shock than those with a disease or
infection such as coccidiosis. Weaning shock may be more
severe for kids weaned prior to 4 or 6 weeks, but the tem-
porary weight loss is usually overcome by subsequent
compensatory growth.
Measurement of Growth
Growth in animals is usually determined by producers
with easily obtained measurements, such as age, length,
height, weight, width, or circumference rather than
measuring specifi c physical and chemical components as
is done by scientists. The rate of growth is expressed in
terms of weight or gain per age (weight per day of age),
weight gain per time period, weight change per amount
of time (average daily gain), height at a specifi c age,
time to reach a specifi ed weight, or other easily compared
measurements that provide common points of reference
for growth and development of different animals. Growth
is most often determined as gain in weight. The
average daily gain is the change in weight between two
time periods. Effi ciency of growth and development is
often expressed as the output divided by the input, with
weight of gain per weight of feed input a common
measurement.
Pre - Weaning Growth Rates
It may be expected that healthy kid goats grow at least
one - third to one - half pound (150 - 225 g) per day during the
fi rst 3 months of age. Comparisons in growth rate or of
average daily gain of kid goats must consider the factors
that infl uence growth. Kid goats from the smaller breeds
will tend to grow slower than kids from the larger breeds,
and kid goats from earlier maturing breeds will have a
faster growth rate than kids from later maturing breeds.
Buck kid goats grow 10-25% faster to weaning than doe
kids (Warmington and Kirton, 1990). Kids from triplet
