Íslenskar landbúnaðarrannsóknir - 01.09.1975, Side 57

ÍSL. LANDBÚN.
J. AGR. RES. ICEL.
1975 7, 1-2: 55-62
Occurrence and inheritance
of tan colour in Icelandic sheep
Stefan Adalsteinsson,
The Agricultural Research Institute,
Keldnaholti: Reykjavík, Iceland.
ABSTRACT
The paper summarizes results from several investigations on the occurrence and inheritance of tan
fibres in Icelandic sheep carried out in Iceland during the years 1956—1971. In 204 adult rams,
0.6 per cent of the fibres showed tan colour and had an average diameter of 97.4 micron, com-
pared to 30.7 micron for whole wool samples.
A highly significant connection has been found between: a) score for tan colour at birth and
amount of tan colour in lamb pelts at weaning at 4—5 months; b) score for tan colour at birth
and amount of tan fibres in wool of adult ewes; c) amount of tan colour in lamb pelts at wea-
ning and amount of tan colour in flecces at shearing 5—6 months later; d) amount of tan in
pelts of parents at weaning and tan in pelts of progeny at weaning.
Amount of tan in lamb pelts at weaning has been given the following numerical values: 10 = no
tan colour present; 5 = tan on head and feet but not on body; 0 = tan fibres on body.
The heritability of these pelt classes has been found to be 0.46 ± 0.05 by regression of offspring
on midparent ('601 progeny).
A comparison of 240 lambs by '6 sires without tan fibres with 216 lambs from 8 sires with
tan fibres on body showed nonsignificent difference in carcass weight.
In a selection experiment, 272 ewes without tan colour showed slightly lower lamb production than
665 ewes with tan colour, presumably due to lowered selection differential for weight when the
ewes without tan colour were selected for breeding.
Lamb production of 339 two year old daughters from 30 sires without tan colour did not differ
significantly from lamb produaion of 341 daughters from sires with tan colour.
INTRODUCTION
The Iceland breed of sheep, the only sheep
breed in the country belongs to the North
European horned, Shorttailed group of sheep.
It was brought to the country, mainly from
Norway, at the time of settlement during the
period 874—930, and influence of other
breeds on this native breed are believed to
have been negligible. (Sigurdsson, 1937;
PÁLSSON, 1944.)
The wool of the Icelandic sheep is predo-
minantly a mixture of long, rather coarse
outercoat fibres and short, fine undercoat.
Some white and tan kemp fibres also occur
(Adalsteinsson, 1956). It has been sug-