Íslenskar landbúnaðarrannsóknir - 01.03.1971, Blaðsíða 12

10 ÍSLENZKAR LANDBLJNAÐARRANNSÓKNIR
hæfur munur á niilli blendingshópanna.
Samanburður á afurðastigi þrevetlnanna
sýnir, að munur milli stofnhópanna er lítill
og hvergi raunhæfur, nema vestfirzki stofn-
inn kollótti hefur raunhæft lægra afurða-
stig í 95% tilfella, en hálfblóðsærnar F2
og blendingar, sem eru meira en 50% þing-
eyskir.
Þetta sýnir, að frjósemi hyrnda stofnsins
vestfirzka hefur aukizt mikið við íblöndun
þingeyska fjárins, en mjólkurlagnin hefur
lítið sem ekkert breytzt við íblöndunina,
er bendir til þess, að sá eiginleiki sé svip-
aður í báðum stofnum.
Athyglisvert er, að um blendingsþrótt í
fyrsta ættlið er ekki að ræða, hvorki varð-
andi frjósemi né mjólkurlagni. Enn fremur
bendir tafla 3 til, að með tilliti til frjó-
semi og mjólkurlagni sé fremur ávinning-
ur að blanda vestfirzka hyrnda stofninn
meira en minna með jhngeysku blóði.
SUMMARY
COMPARISION OF PRODUCTIVITY
BETWEEN DIFFERENT STRAINS OF ICELAND EWES
Halldór Pálsson and Stefán Sch. Thorsteinsson
Agricultural Research Institute, Reykjavik, Iceland
A comparison is made between different strains of Jceland ewes at the Experi-
mental Farm Hestur regarding two important economic characters, fecundity
and milk yield as measured by points given for dressed carcass weight of lambs
at weaning, corrected for age, sex and type of birth. Only two ancl three year
old ewes are compared as up to that age no culling had taken place on account
of low productivity.
In 1951 the Experimental Farm Hestur was restocked with bought-in lambs
frorn commercial flocks from the North-West peninsula of Iceland of two
strains, pollecl and hornecl. These two strains were not interbred.
Comparision of the ewes born in 1951 of these two strains did not show
significant difference in fecundity whereas the ewes of the pollecl strain got
higher points for dressed carcass weight of lambs both as two years old and
three years old and significantly so at the latter age.
By the use of A.I. an horned strain of sheep from North-East Iceland has
been crossed witli the hornecl North-West strain at Hestur, producing cross-
bred ewes with varying amount of the North-East blood by the repeated use
of A.I. and by interbreeding the crossbred sheep in the flock. However, still
some of the horned North-West strain has been kept purebred. The crossbred
ewes were divided into 4 groups, i. e. those with less than 50% N-East blood,
those with 50% N-East blood of the F-, generation, those with 50% N-East
blood F2 and later generations and those with more than 50% N-East blood
and comparecl inter se as well as with the purebred N-West liorned strain.
All the groups of the crossbred ewes had significantly greater fecundity than
the purebred North-West strain both as two and three years old at the 99.5%