Susceptibility of Romney and Perendale sheep to flystrike by the
Australian Green Fly, Lucilia cuprina (Wied.), and fly attractant
trials
G.L. Blackwell, M.A. Potter, Y.H. Cottam and H.T. Blair
Department of Ecology, Massey University, Private Bag 11222,
Palmerston North.
Proceedings of the New Zealand Society of Animal Production. 1997,
57: 37-40
The incidence of flystrike in New Zealand flocks is about 3% in
most years. This low level of prevalence makes it difficult to
discriminate between potential flock replacements based on naturally
occurring flystrike. Selection decisions could be improved if either the
rate of flystrike could be raised artificially or an easily measured
trait that has a higher level of occurrence could be found. The second
approach is used in Australia where fleece-rot has both a higher
incidence rate than flystrike and is highly genetically correlated to
susceptibility to flystrike. However, the incidence of fleece-rot in New
Zealand dual-purpose sheep is not sufficiently high to allow its use as
an indirect indicator. In a effort to find a means of artificially
increasing the incidence of flystrike, groups of hoggets were brought
indoors and exposed to the Australian green fly Lucilia cuprina. In
total, 5 trials (10 animals/treatment) were run to compare: the
susceptibility of Romney vs Perendale sheep, using wetting, dung or
homogenised liver as attractants. Wetting was applied along the back
from a watering can while the other attractants were applied to a patch
on the shoulder, mid-back and rump. About 2000 gravid flies were
released into a fly-proof room along with the penned sheep. The main
results of these trials were: a) It was very difficult to get an
established maggot population on clean wet sheep; few eggs were laid and
no cases of established strike occurred; b) Dung acted as a moderately
successful attractant; maggots were hatched on the sheep but none
developed to the skin penetrating stage; c) Liver acted as a very
successful attractant and maggots developed on all treated sheep. No
between-breed differences occurred with wetting, dung or liver
attractants. Further studies are required to refine the use of
attractants. In particular, an attractant that is less powerful than
homogenised liver but more potent than wetting or dung is required
before moving onto large-scale field trials.
Keywords: NZSAPAB;
Flystrike; fly attractants; selective breeding
Last Updated 12-09-1998
