New Zealand Journal of Agricultural Research abstracts
Estimates of genetic parameters for production and reproduction traits in three
breeds of pigs
M. T. SKORUPSKI
D. J. GARRICK
H. T. BLAIR
Department of Animal Science
Massey University
Palmerston North, New Zealand
Abstract Restricted Maximum Likelihood (REML) procedures for
multiple trait animal models were used to estimate heritabilities, genetic
correlations, and common environmental effects for average daily gain (ADG),
backfat thickness (BF), and number of pigs born alive per litter (NBA). Data
included 5561 litter records and 38622 ADG and BF individual performance
records for on-farm-tested Large White, Landrace, and Duroc pigs fed ad libitum
from three New Zealand nucleus herds recorded over the period 1980-93. A
bivariate animal model for ADG and BF contained fixed effects for
herd-year-season (HYS) of test, sex, and age as a linear covariable, as well as
random litter and animal effects. The NBA model included fixed season of
farrowing and parity effects, and random animal (sow) and permanent
environmental effects. Repeated records for NBA were accommodated by fitting a
permanent environmental effect, uncorrelated to additive genetic effects, for
each sow. The estimates of heritability (h2) for ADG were
0.20, 0.18, and 0.16, and the estimates of the litter variance in proportion to
the phenotypic variance (c2) were 0.11, 0.12, and 0.09 for
Large White, Landrace, and Duroc breeds, respectively. The h2
estimates for BF were 0.44, 0.45, and 0.46 for Large White, Landrace, and Duroc
breed, respectively, and proportionate c2 estimates were 0.06
for all breeds. The phenotypic, genetic, and litter correlations between ADG
and BF ranged from 0.32 to 0.54. The h2 estimates for NBA
were 0.13, 0.09, and 0.16, permanent environmental variance ratios
(m2) were 0.06, 0.05, and 0.05, and repeatability estimates
(t) were 0.19, 0.14, and 0.21 for Large White, Landrace, and Duroc
breeds, respectively. Correlations found in this study between ADG and BF
indicate that selection to improve one trait may be associated with
unfavourable change in the other trait. Therefore, a multiple trait selection
procedure such as a selection index is required to accommodate these
antagonistic associations between traits.
Keywords animal model; genetic evaluation; pigs; restricted
maximum likelihood; variance components
New Zealand Journal of Agricultural Research, 1996, Vol. 39: 387-395
0028-8233/96/3903-0387 $2.50/0 (c) The Royal Society of New Zealand
1996
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