Sheep - AgRIS

humidity and high solar radiation will not produce good quality semen during hot dry and hot
humid seasons. Females oftropical breeds cycle throughout the year. Temperate breeds which
are affected by hours of day light and breed with declining day length. They come in heat in
autumn from August to November, although some may breed up to February.
9.5.1 Natural Breeding (Individual, Pen and FlockManng)
The natural breeding is done either by flock mating penmating & hand mating. In flock
mating system. Sheep can be bred naturally or through artificial insemination. The natural
breeding is done by either flock mating, pen mating or hand mating. In flock-mating system,
breeding rams are usually turned out in the flock during the mating season at the rate of 2 to 3
per cent of the ewes all through day and night. It is most widely practised in the flocks of all
farmers. Semi flock breeding or pen breeding is done to conserve the energy of rams and give
them rest. In this, the rams are turned out for service with the flock in the pen during night, and
confined and stall-fed or grazed separately during the day time. Hand mating is practised when
exotic purebred sires are used, or when it is considered desirable to extend the services of ram
over much larger flocks. Sheep in heat do not manifest behavoioural symptoms. Hence, the
teaser rams are employed for detecting the ewes in heat. These ewes are then taken out of the
flocks and bred to the designated sire of the flock. In pen and hand-mating systems and when
teaser rams are used for heat detection some dye mixed in grease or simple linseed oil is
smeared on the brisket of the ram. This makes it possible to record the date when the ewes is
bred and also to remove them from the breeding flock. The colour of the dye should be changed
every 16 to 18 days so that the repeaters can be discovered, if the bred ewes have not been
removed from the flock. This is termed as marking of ewes by breeding ram and marked ewes
are considered as bred.
9. 5.2 Artificial insemination
It is beacause of this that the possibility of artificially inseminating females exists. From
four to eight ewes may be inseminated from one service of a ram—although as many as 30 to
40 have been reported, but the degree of success was not given as 0.1 to 0.2 cc of semen is
sufficient for the purpose when there is a heavy concentration of sperm in the semen. Great
numbers of sperm are of course needed as they are microscopic in size, and the reproductive
tract of the female through which they must migrate to come in contact with the egg, also
microscopic, is very large indeed in relation to the size of the reproductive cells. Apparently,
most sperm do not survive much more than 18 to 24 hours in the reproduction tract of the ewe.
Russian research workers have reported impregnating from 300 to 400 ewes in one season with
the semen collected from a single ram. They also reported that 90 percent of the ewes so
insemianted became pregnant. This is a far greater number than could be bred to one ram using
natural methods. From 40 to 60 ewes is generally considered a reasonable/maximum for a ram
in one season.
For the purpose of artificial insemination, artificial vaginas are used for the collection ofthe
semen, alSough it may be recovered in some quanitity from the vagina of an ewe. Semen can
be preserved for several days with suitable media and low temperature and has been transported
long distances and used successfully in experimental tests. The semen is diluted for use and is
injected into the vagina or deposited at the base of the cervix through a glass or plastic tube.
Two inseminations at about a 12 hour interval, beginning soon after the onset of heat, are often
recommended.
Although little use has been made of artificial insemination in sheep except in an
experimental way, some of the advantages and disadvantages are known. The chief advantages
are that the usefulness of a superior sire may be greatly extended, the number of rams needed
for a large flock is reduced, and a flock of considerably greater uniformity should result.
Disadvantages include the need for extra equipment and labor, some of which must be skilled
in the work, the need for one or more "teasers" to identify which ewes are in estrus, and the
frequent handling of the ewes during the breeding season.
9. 5. 2.1 Heat detection methods
Visual signs of approaching estrous are, a swelling and redness of the vulva and
restlessness or nervousness indicating a desire for company, but the most abvious sign is
ridding and inturn being ridden. The breeding occurs only during estrous although the ram is
capable of breeding at any time.
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