Íslenskar landbúnaðarrannsóknir - 01.03.1970, Side 76

74 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
TABLE 36
Least squares estirnates of effect of colour genotypes of ewes and rarns
on number of lambs per mating
Estimated deviations of
Genotype of parent Ewes Rams
No. of matings Among all White vs. nonwhite No. of matings Among all White vs. nonwhite
1. Three year old ewes.
Overall mean (unadjusted) = 1.282
Ai— 1816 - 0.077 942 0.011
AiAi 599 -0.019
AiAj, i 1 208 - 0.028 518 0.033
White 2024 - 0.088 2059 0.016
Nonwhite 412 0.105 0.088 377 - 0.025 -0.016
2. Four year old ewes.
Overall mean (unadjusted) = 1.370
Ai— 1459 - 0.074 783 0.028
AiAi 512 0.000
AiAj, i^l 243 -0.003 414 - 0.006
White 1702 -0.067 1709 0.013
Nonwhite 309 0.077 0.067 302 - 0.022 -0.013
comparable estimates in table 32. Tliis is
to be expected when it is considered tliat
the ram genotypes were not taken into
account in table 32, and it is seen from
table 34 that they may have inflated the
estimates in table 32.
The effect of colour genotype of the
rams on number of lambs per ewe lamb-
ing in tabie 34 is not significant. It is
noticeable, however, that the estimated de-
viations for rams have the sarne sign as
those for the ewes, but their magnitude is
less.
As regards the effect of colour genotypes
of ewes and rams on number of lambs per
mating, several points of interest emerge
from tables 34—37. Tlie effect of allele At
in ewes is almost the same as that found
with respect to number of lambs per ewe
lambing, which indicates that the effect of
the allefe is operating at a very early stage
of gestation, because a refatively high pro-
portion of the matings resulting in no lamb
is due to return of the ewe on heat.
Among matings with known genotypes at
the A-locus, 183 matings resulted in no
lamb. Of these, 112 or 61.2 per cent, were
due to ewes coming back on heat, while 47
ewes aborted and 24 were barren. If this
failure to conceive was unaffected by the
A^-allele, one woulcl have expected a great-
er discrepancy than that observed between
the estimated deviations for wliite antl non-
white ewes in part 1 and 2 of table 34.
It is seen frorn table 35 that the colour
genotype of the ram has a significant effect