| Issue |
Genet. Sel. Evol.
Volume 37, Number 2, March-April 2005
|
|
|---|---|---|
| Page(s) | 199 - 213 | |
| DOI | https://doi.org/10.1051/gse:2004044 | |
DOI: 10.1051/gse:2004044
Genetic parameters and responses of performance and body composition traits in pigs selected for high and low growth rate on a fixed ration over a set time
Nguyen Hong Nguyena and Cameron P. McPheeba School of Veterinary Science, University of Queensland, QLD 4072, Australia
b Animal Research Institute, Queensland Department of Primary Industries, Australia
(Received 26 May 2004; accepted 11 October 2004)
Abstract -
Two lines of Large White pigs of common genetic origin
were divergently selected over four years for high and low growth rate
during a 6 week post-weaning test period in which all pigs were fed the same
total amount of food (80% of estimated ad libitum intake). Genetic parameters and
direct and correlated responses in performance and carcass traits were
estimated on 2884 pigs with pedigrees comprising a total of 5324 animals,
with restricted maximum likelihood and best linear unbiased prediction
methods applied to a multi-trait animal model. Estimates of heritability
(
SE) were
for lifetime daily gain (LDG),
for test daily gain (TDG),
for ultrasound P2 backfat
(UBF) and
for food conversion ratio during test (TFC), and
for daily carcass weight gain (CDG),
for
carcass backfat (CFT) and
for carcass lean percentage
(LEAN). Common litter effects for TDG, UBF and TFC were less than 5% and
for LDG, 17% of total phenotypic variance. Genetic correlations between
performance and carcass traits were moderately to highly favourable. After
four years of divergent selection for growth rate, the selection responses
in estimated breeding value (EBV) for TDG were 40.14 and -41.11 g (SED
2.95) for the high and low growth lines, respectively. The regressions of
EBV on year of birth, indicate that the annual genetic trend for TDG, was
8.73 g/yr in the high and -8.48 g/yr in the low lines (
P<0.001).
Correlated genetic responses in the high and low lines respectively were
5.28 g and -12.40 g (SED 2.09) in LDG, -0.35 mm and 0.56 mm (SED 0.009) in
UBF, -0.145 units and 0.185 units (SED 0.012) in TFC, 3.17 g and -10.97 g
(SED 1.53) in CDG, -1.13 mm and 1.01 mm (SED 0.155) in CFT and 1.24% and
-1.27% (SED 0.150) in LEAN. It was concluded that selection for increased
post-weaning daily gain on a ration of fixed amount reduces the age at
slaughter and the level of backfat and increases the efficiency of food
utilisation, weight and leanness of pig carcasses.
Key words: divergent selection / pig / growth / restricted feeding / genetic responses
Correspondence and reprints: nhongnguyen@yahoo.com
© INRA, EDP Sciences 2005