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Genetic parameters for faecal egg count following mixed, natural, predominantly Ostertagia circumcincta infection and relationships with live weight in young lambs

Published online by Cambridge University Press:  02 September 2010

S. C. Bishop ,
K. Bairden ,
Q. A. McKellar ,
M. Park  and
M. J. Stear
S. C. Bishop
Affiliation:
Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS
K. Bairden
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
Q. A. McKellar
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
M. Park
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
M. J. Stear
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
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Abstract

Faecal egg counts and live weights were measured on approximately 200 predominantly twin-born Scottish Blackface lambs each year for 3 years, from 1 to 6 months of age. Measurements were made at 4-week intervals following anthelmintic treatment. Heritability estimates (with s.e.s) of log transformed faecal egg count at each age were 0·01, 0·00, 0·12 (0·10), 0·14 (0·12), 0·15 (0·07) and 0·22 (0·13), for ages 1 to 6 months respectively. Therefore, genetic variation exists for acquired but apparently not for innate resistance to infection. Maternal common environmental effects (with s.e.s) were 0·36 (0·11), 0·20 (0·05), 0·27 (0·09), 0·06 (0·08), 0·15 (0·09) and 0·16 (0·08), for ages 1 to 6 months respectively. Genetic correlations between faecal egg counts in lambs older than 3 months were not significantly less than 1·0, indicating that faecal egg counts at different ages are expressions of the same trait. Phenotypic correlations between faecal egg counts were generally positive but small. Measurement error contributed one-third of the observed variation for individual egg counts. The heritability of mean faecal egg count from 3 to 6 months was 0·33 (s.e. 0·15), indicating that selection decisions can be made more accurately using multiple egg counts per animal. Phenotypic correlations between faecal egg counts and live weight were generally negative but close to zero. However, genetic correlations between faecal egg counts and live weight in lambs older than 3 months were close to -1·0, indicating that resistance to gastrointestinal parasites may be an important genetic determinant of growth rate in this environment.

Keywords

faecal egg countsgenetic parameterslive weightOstertagiasheep
Type
Research Article
Information
Animal Science , Volume 63 , Issue 3 , December 1996 , pp. 423 - 428
Copyright
Copyright © British Society of Animal Science 1996

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