Íslenskar landbúnaðarrannsóknir - 01.03.1970, Blaðsíða 8

6 ÍSLENZKAR LANDBUNAÐARRANNSÓKNIR
4. If the ewe does not conceive at the first
rnating, and another ram is used at
the seconcl heat, this change of ram
may not be entered into the recorcl
book.
5. Rams may occasionally break out of
their pens and into the ewe pens. Then
they are usually assumed to have mat-
ecl all the new ewes on heat in the
pen where they are found. If ewes from
previous day’s mating are still on heat
in that pen, they are assumed to have
conceived at the rnating the previous
day, and not to the second ram, and
no account is given of sucli incidences
in the record books.
6. The original records of the matings
are usually made in notebooks, and
transferred from there to the ilock
books. Sorne errors may occur during
this transcription of the records.
The most likely source of faulty recorcls
among those listecl above is accidental mat-
ing by the teaser ram, although the other
sources can not be excluded.
On relatively few farms in the country,
the ewes which it is intended to mate to
a particular ram are put into a separate
pen and the ram let loose in that pen. No
measures are then taken to determine
how many and which ewes are on heat
each day. This system is not widespread.
It was used on only one of the farms where
the colour inheritance data were obtained.
4. Supervision at lambing time
The lambing season usually starts some
time between the 5th and 25th of May.
The lambing may take place either in the
sheds or outdoors, but the earlier the lamb-
ing is the more likely it is to take place
in tlie sheds.
When the lambing takes place in the
sheds, it occurs every now and then that
two ewes, one or both giving birth to
twins, lanrb almost simultaneously and very
close together. Then the ewes themselves
don’t discriminate between their own
lambs and the other ewe’s lambs. If this
happens when nobody is supervising the
sheep, the supervisor will try to sort out
the mess when he arrives. If one takes for
the sake of argument, a case where the
farmer finds two ewes sharing 5 newborn
lambs, when he enters the shed, he will
give the three lightest lambs to the ewe
which is known to be rnore fertile. He may
in case of similar sized larnbs, look for
other signs which might indicate the cor-
rect mother of each lamb. If one or rnore
of the lambs are nonwhite, and one of the
ewes has earlier given birth to nonwhite
lambs, she will most likely by given the
nonwhite lamb or lambs. Incidents of this
kind are rarely recorded in the flock books.
The decision the supervisor makes is re-
garded as the correct one, and the incident
is forgotten.
It frequently happens when lambing
takes place in the sheds, and occasionally
outdoors, that ewes which are about to
lamb try to steal a lamb from another ewe.
Sometimes they are successful, particularly
if they come across a ewe which has al-
ready given birth to one twin and the se-
cond twin is being born. If this happens
during a period of no supervision, the re-
sult is a permanent fault in the record.
Mismothering, as described above, will
always be a relatively rare phenomenon,
and with careful supervision at lambing
time, mismothering should not occur at all.
But this possibility has to be recognized
when dealing with sheep records from com-
mercial flocks, where rouncl the clock super-
vision at lambing time may be very diffi-
cult to achieve. The farms where the re-
cords in the present studv were collected
are all regarded as having relatively close
supervision of ewes at lambing time. The
possibility of faulty records clue to mis-
mothering can not, however, be excluded.