New Zealand Journal of Agricultural Research abstracts
Faecal egg count and food intake comparisons of Romney
single-trait selection and control lines
C. A. MORRIS
J. N. CLARKE
T. G. WATSON1
A. L. WRIGGLESWORTH
J. L. DOBBIE
AgResearch
Ruakura Agricultural Research Centre
Private Bag 3123
Hamilton, New Zealand
1Present address: Pfizer Laboratories Ltd, CPO Box 3998, Auckland,
New Zealand.
Abstract Two sets of correlated responses were studied in
five Romney selection lines and their controls. The lines were from one
experiment selecting for yearling body weight or yearling fleece weight since
1967, from a second experiment selecting for weaning weight or yearling fleece
weight since 1973, and from a third experiment selecting for yearling body
weight since 1973. Overall, the five selection lines were evaluated whilst
being run together with controls at a single site. The responses were faecal
egg count (FEC) after weaning, using lamb crops born in 1990-93, and food
intake using 1993-born 7-month-old ram lambs. Four or five new sires were used
per line per year, with 1471 and 232 animals being recorded for FEC and food
intake respectively. The three body weight lines were each 20-22% heavier than
their respective controls in March (6 months of age) and May. Average FEC over
this time period was significantly greater by 63% in one of these three lines
whereas there was no difference from the control in the other two body weight
lines. The two fleece weight lines were 10-11% heavier in March-May, with
34-35% heavier yearling fleece weights, than their respective controls, whereas
average FEC was significantly greater (by 35 and 46%) in both selection lines.
Significant correlated increases in estimated food intake were recorded in all
three body weight lines and in one of the two fleece weight lines, and these
increases were proportional to the liveweight response. The implications of the
correlated responses and their variability are discussed.
Keywords sheep; selection; body weight; fleece weight; faecal
egg count; food intake
New Zealand Journal of Agricultural Research, 1996, Vol. 39: 371-378
0028-8233/96/3903-0371 $2.50/0 (c) The Royal Society of New Zealand
1996
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