Sheep - AgRIS

dwarfs (CC) to produce all comprest (Cc) because the mortality rate of the comprest dwarfs is
so high that they do not survive to maturity and cannnot be used for breeding purposes.
An important fact concerning selection when dominance is incomplete is that the genotype
can be determined by inspection of the phenotype. Therefore, an undesirable gene can be
eliminated from the herd by discarding all heterozygotes.
5. 5.3 Conformanon
Desirable type and conformation have also received attention in sheep as in other classes of
farm animals. With this species, however, attention must also be paid to selection for wool
production in addition to mutton quality and rate and efficiency of gains.
Animals possessing very obvious defects, such as over-shot jaws, undershot jaws, black
wool, wool-blindness, skin folds, shallow bodies, and poor mutton qualities, should be culled
from the flock. If animals with these defects are elimmated from the breeding lock and
selections are made on the basis of body weight and quantity and quality of wool, especially in
the selection of rams, perhaps this will amount to proper attention to type.
Ewes which may be highly productive yet have some objectionable characteristic may be
mated to a ram that is especially outstanding in the trait in which the ewes are inferior. Many
times this corrects the fault in just one cross. This is a principle of mating that could be used to
improve many traits and is effective, as shown by the history of the development of the many
present-day breeds of farm animals.
5. 5.4 Wool and hair Types
The main differences between hair and wool are: wool fibers are usually much smaller in
diameter; the epidermal cells of hair are fastened to the cortex throughout their length; hair is
always medulated; hair never is crimped like fine wool, although some is wavy like the coarser
wools; both hair and wool may have pigment within the cortex, but most wool is free of
pigment. Wool fibers grow much denser on the skin than hair grows. In vely dense-fleeced,
fine-wool sheep there may be more than 50,000 fibers per square inch of skin area. In the
coarser, loose fleeced sheep the number may not exceed 5,000 per square inch.
Wool is one of the natural fibres of animal origin which is hygroscopic. It is a protein fibre
and the protein is called Keratin because it contains sulphur bearing amino acids. The main
sulphur containing amino acid cystein forms the basic linkage in wool through disulphide
bonds. This fibre has a small diameter of the order of 103 to 10-4 compared to its length going
upto 10-12 cm. This property gives it an important place among textile fibres. Its chemical
constituents are mainly about 18-20 amino acids linked through CONH bonds forming the
polypeptides which give softness and resiliency, suitable for a textile fibre. Also its surface
structure, the cuticle has scales which provide cohesion in the fibres when they are twisted into
yarn. The chemistry of the fibre is most suitable for easy dyeing nd other wet processes.
Quality evaluation of textile materials is very important to utilize them for appropriate
products. The properties of the yarn and fabric depend largely on the fibre arrangement and
fibre properties. It is therefore important to know the fibre quality.
The fleece in wild or less developed sheep breeds contains 3 types of fibres, viz. wool, hair
and kemps. The true wool fibres are relatively fine and 15 to 50µ in diameter. Kemp fibres are
very coarse (100 to 200µ) brittle, tapered, heavily medullated and short because of their limited
growth. Hairy or hetertype fibres have a network of hollow, air-filled cell-walls (medulla). The
medullated portion can be fragmented, interrupted or continuous. Medulla is commonly found
in wools coarser than 30µ. The carpet wools are evaluated in terms of average fibre diameter,
staple length and percentage of medullated fibres, viz. kemp and heterotypes.
Variations in wool covering in different sheep are extremely large. Some sheep have wool
fibers that are hard to distinguish from hair. In some, only the main portion of the body is
covered, while in others the wool extends from just above the nostrils to the feet. Wool on any
one sheep is never uniform in length or fineness. The finest and densest wool fibers are found
on the shoulders, about midway between the top of the shoulders and floor of the chest; the
coarsest wool is about the breech and dock, the shortest wool is usually on the belly. Sheep
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