Genetic effects in GrowBulk sheep
J.N. Clarke, R.M.W. Sumner and N.G. Cullen
AgResearch, Ruakura Research Centre, Private Bag 3123, Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1999, 59: 14-16
GrowBulk sheep are a strain of long-wool type sheep growing high
bulk wool developed by introgressing high-bulk genes from Texel and
Dorset rams into Romney ewes. Progeny selection was planned to minimise
decreases in clean fleece weight. Rams have been released to four
multiplier flocks. Genetic effects were evaluated in the nucleus and
multiplier flocks using a restricted maximum likelihood animal model.
Heritability estimates were 0.46±0.05 for bulk and 0.30±0.05
for clean fleece weight with a genetic correlation of -0.48±0.09.
The crossbred genotypes represented in the nucleus flock showed a range
in average breeding merit for bulk of 27 to 31 cm³/g, their weighted
mean genetic superiority over contemporaneous Romneys being 5.3 cm³
/g. The first crop of commercial progeny by rams from this flock showed
an average genetic superiority in bulk over their dams of approximately
4 cm³/g. Genetic trends indicate that selection has been able to
maintain the bulk advantage of the crossbreds while at the same time
improving their fleece weight.
Keywords: NZSAPAB;
wool bulk; genetic parameters; selection responses; outcross performance.
Last Updated 06-08-1999
