Sheep - AgRIS

produced on rations which contain increased amounts of some minerals, the increase is below
the added cost of such feeding at the present time.
Properties of wool as elasticity, pliability, and softness may be influenced by environment,
breed and nutrition, and individual in heritance. Studies have been made to determine how
these features of the wool fiber are related to the external and internal structure of fibers.
Further, it is possible that differences in the readiness with which various wools are dyed may
be related to structural differences or to chemical differences.
In general, wool may be described as showing considerable variation in many of its
properties. Many difficulties are encountered in research work on wool fibers because of the
interrelationships one factor may have to a host of other factors. Thus, the sulphur content of
wool may have a relationship to its elasticity, but other items may have equally important
influences on elasticity or on some other characteristic.
Wool absorbs and holds moisture so that it is released slowly. The absorption of moisture
causes some changes in the fiber, especially in diameter. The swelling of wool from an air-dry
to a saturated condition may amountto almost 15 per cent. From a condition of complete
dryness, the swelling would be considerably greater.
Most work reported on wool fibers has been done without completely controlled
conditions, and this has caused difliculty in comparing reports of variou4s investigators. In the
absorption of water, wool evolves heat. A 45 gm thoroughly dry wool, in changing to a
thoroughly wet condition, is reported as evolving 43 British Thermal Units. This is an unusual
fiber quality. Wool releases its moisture slowly.
Electricity and heat transfer through wool is slow. Undoubtedly, part of the low
conductivity of heat is due to the numerous air cells which fabrics made of wool may contain.
However, the conductivity of the fibers is also low.
Wool is not quickly inflammable, but it will burn and gives off a very disagreeable odor. It
is very different from cotton, which burns readily. When wool is burnt, a charred bead remains
where the burning has stopped. These differences serve; as one easy means of distinguishing
between wool and some other materials. If the material in question contains a mixture of
several fibers, the so called burning test is of no value, and more accurate chemical or
microscopic means are needed. Because wool is subject to severe damage when exposed to
caustics, strong acids, and high temperatures, either moist or dry, care must be used to preserve
its original qualities during the scouring and other manufacturing processes and also after it has
been completely fabricated. These are the reasons why carbonizing of burry wool, for example,
is a rather slow and costly process. Washing of woolen materials must be done with neutral
soap—that which contains no free alkali—and the temperature of the bath must be in the
neighborhood of 120 degrees F. Vlolent agitation of the bath is apt to cause shrinkage of a
fabric or a felting tendency of unmanufactured wool.
Because of its elasticity, the best quality wool gives to fabrics a striking ability to recover
from crushing or compression or from temporary stretching. When the pressure used in baling
wool is released, this resiliency causes the wool to increase gradually in bulkiness. It is this
property too which causes wool to "drape" becomingly on the human form and to retain the
"shape" into which it is pressed when moist and is dried during the process of pressing.
5.6 Inheritance of Quantitative traits
In quantitative inheritance, many pairs of genes are involved, and there is no sharp
distinction between the different phenotypes, the differences being ones of degree only. Many
traits in farm animals which are of the greatest economic importance are good examples of this
kind of inheritance, including fertility, rate of gain, efficiency of gain, milk production, and
carcass quality. The expression of these traits is affected by many pairs of genes as well as by
environment.
Since, in quantitative inheritance, the phenotypes are no distinct and separate but exhibit a
series of varations between the extremes, mathematical methods have been devised for
measuring and describing populations. Some of these methods are given below:
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