Faecal nematode egg counts and facial eczema susceptibility in
Romneys
C.A. Morris, N.R. Towers, T.G. Watson, M. Wheeler, N.C. Amyes
and B.C. Hosking
AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123,
Hamilton, New Zealand.
Proceedings of the New Zealand Society of Animal Production, 1996,
56: 84-86
A study was carried out in two groups of flocks to estimate the
relationship between susceptibility to facial eczema (FE) and susceptibility
to nematode parasites. Faecal egg count (FEC) data on lambs born in 1989-
92 from 53 sire groups were collected on the Ruakura Romney flocks which
have been divergently selected for resistance/susceptibility to FE. In
addition, the Romney flocks selected at Rotomahana/Tokanui Stations for
resistance/susceptibility to FEC were sampled to provide the converse (i.e.
FE data) on lambs born in 1988 and 1989, and representing 43 sires. Faecal
samples for FEC were collected from lambs in January and March
(separated by an anthelmintic treatment) and the FEC data were analysed
using a loge transformation. FE susceptibilities, using the enzyme gamma-
glutamyltransferase (GGT) as an indicator, were obtained in the FE flocks at
Ruakura after an oral sporidesmin challenge in May, and in the FEC flocks
at Tokanui after unintentional field challenge; the GGT data were also
analysed using a loge transformation. The weighted average heritabilities of
loge GGT and loge (FEC+100) were 0.44±0.03 and 0.33±0.05, respectively.
At Ruakura, the two traits had a genetic correlation of 0.15±0.15, and at
Tokanui, the corresponding correlation was 0.22±0.12, with a combined
estimate of 0.19±0.09 (P<0.05). These results indicated that there was a
tendency for the two traits to be positively associated among sire groups,
when both types of challenge were applied in sequence.
Keywords: NZSAPAB;
nematodes; faecal egg count; facial eczema; correlation; sheep.
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Last Updated 18-03-1997
