Íslenskar landbúnaðarrannsóknir - 01.03.1970, Blaðsíða 7

COLOUR INHERITANCE IN ICELANDIC SHEEP 5
by law, be housed from the beginning of
November, as the ewes may start coming
on heat during the first or second week
of November.
The beeding season usually starts from
15th—30th of December, varying somewhat
from one part of the country to another.
3. Detection of ewes on heat
Because correct information about par-
entage is of vital importance in connec-
tion with inheritance studies, a detailed
description of the practices followed dur-
ing the breeding season seems justified.
During the breeding season, the most
common practice is to take an entire
teaser ram to the shed where the ewes are
kept. This ram is led by a rope, tied
around the base of the liorns on horned
rams, but around the neck on polled rams.
The ram is allowed to run into the ewe
pen ahead of the man who leads him, and
care is then taken that the ram only de-
tects ewes on heat without serving them.
The ewes on heat are usually taken out
of the pen, when they have been detected,
as they will otherwise distract tlie ram
from further search. If only one man is
on the job, he has to tie the ram securely
inside the pen, while he takes out the de-
tectecl ewes. If the ram is loosely tied, he
may then serve ewes on heat, which still
remain in the pen.
In order to ensure that the teaser ram
does not serve the ewes accidentally, some
farmers tie a jute apron under tlie belly
of the teaser ram, before lie is taken into
the ewe pen. Tliis is the practice on the
Agricultural Reasearch Institute’s Experi-
mental Farm at Hestur, where much of the
data in the present study were collected,
but relatively few farmers use this practice.
After the ewes on lieat on a particular
day have been detected, they are taken to
a place near the rams’ pen, where the mat-
ing takes place. Tlie farmer has usually
decided beforehand to wliich ram each ewe
is to be mated, and the ewes are then in
turn mated to the rams they have been as-
signed to.
Each ewe is ordinarily only mated once
during the heat. Sometimes a ewe may be
remated to the same ram the next day, if
she is still on heat, but this is not ordin-
ary pratice during the peak of the mating
season, as the number of rams available is
usually limited, and tliis would mean a
much heavier use of each ram. Repeated
mating may, however, be used during the
second heat of a ewe, i.e. if she has failed
to conceive at the first heat.
Usually only one round is done each day
in the ewe pens to detect ewes on heat,
and the mating generally takes place from
0—2 hours from detection. Tlie ewes may
thus have been on lieat from 0—26 hours,
when the mating takes place, and on the
average about 12—13 liours.
This system of mating should give ac-
curate records of parentage when the super-
vision is carried out with care. The most
likely sources of faulty parentage arising at
the time of mating are the following:
1. Accidental, unnoticed mating of a ewe
with the teaser ram.
2. Mistaken identity of the ewe during
mating causing faulty records, i.e. the
ewe mated is not the one that is re-
corded as being mated. l’lie fault will
eventually be discovered later, when
the ewe, which was thought to have
been mated, comes on heat, but the re-
cord may not be properly corrected.
Mistaken identity of rams during mat-
ing may occur, but is very unlikely.
3. Records of the matings on a particular
day may somtimes be written down
from memory. after all the ewes on
heat that day have been mated. It is
obvious that this practice may intro-
duce errors.