Genetic parameters and performance of flocks selected for
advanced lambing date
J.F. Smith, D.L. Johnson, T.C. Reid
AgResearch, Ruakura Agriculture Centre, Private Bag 3123,
Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production.
1992, 52: 129-132
Data for the years 1986 to 1990 from the "Kamo" out-of-season
lambing flock were subjected to analyses to determine the genetic
variation for lambing date. The response variate was date of lambing
(provided the ewe had a chance to mate for an autumn lambing) and this
was transformed to an underlying normal scale by treating it as an
ordered categorical response. Restricted maximum likelihood (REML)
analyses were performed using an animal model. Year of record and age
of ewe were included as fixed effects. There were 870 ewes having a
total of 1967 lambing records. The estimate of heritability for
standardised lambing data was 0.23 and repeatability 0.36 while the
heritability for litter size was 0.03. Preliminary multivariate
analysis indicated that the genetic correlation between standardised
lambing date and litter size to be 0.09.
At the time of disbanding of the flock samples of ewes selected on the
phenotypic response (i.e. number of times lambed in autumn) of the ewe
or of her dam, were brought to Ruakura. In 1991 following a best linear
unbiased prediction (BLUP) analyses these were assigned to Autumn and
Spring lambing flocks on the basis of their breeding value (BV) for
standardised date of lambing. The average BV for the Autumn flock was -
0.13 while that for spring was +0.07 and there was a 26 day difference
in mean lambing date (167 vs 193).
Keywords: NZSAPAB;
Out-of-season lambing; heritability; genetic parameters; lambing
performance; litter size; selection; breeding values; lambing date;
season.
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Last Updated 25-01-1997
