Íslenskar landbúnaðarrannsóknir - 01.03.1971, Síða 39

KYNBÓTAEINKUNN ÁA 37
Arí'gengið 0.22 á kynbótaeinkunn áa
gefur tilefni til að benda á, að árlegar kyn-
bótaframfarir í afurðasemi sauðfjár ættu
að geta orðið hlutfallslega mun örari en
kynbótaframfarir í nythæð mjólkurkúa,
einfaldlega vegna þess, að ættliðabil sauð-
fjárins er svo miklu styttra en ættliðabil
nautgripa.
S U M M ARY
SELECTION INDEX FOR EWES
Stefán Aðalsteinsson,
Agricultural Research Institute, Reykjavík, Iceland
The paper describes the use of a selection index for Icelandic ewes in which
the four characters: fecundity of ewes, score for lamb carcass production, wooi
weight and wool class are combined into an index. The system for converting
carcass weights of lambs into scores and the construction of the four character
selection index is described in the paper.
The paper further gives the results from the construction of a two-character
index, where only ewe fecundity and score for carcass weight are included. The
respective heritabilities used in the index were 0.15 and 0.30 and index effici-
ency was estimated to be 0.18. This index was calculated on records frorn 2539
two year old ewes which had lambed in spring and rearecl a lamb during
summer.
The heritability of this index, based on a half-sib analysis of variance, was
found to be 0.22 with the standard deviation 0.05. The heritabilities of the
index components, fecundity and carcass score, were found to be 0.21 and 0.21
with the standard deviations 0.05 and 0.05 respectively. Attention is drawn to
the unusually high heritability of fecundity and to the relatively high herita-
bility of the index which should make index selection for increased produc-
tivity well worth while.