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The use of a gamma-type function to assess the relationship between the number of adult Teladorsagia circumcincta and total egg output

Published online by Cambridge University Press:  09 November 2000

S. C. BISHOP  and
M. J. STEAR
S. C. BISHOP
Affiliation:
Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS, Scotland, UK
M. J. STEAR
Affiliation:
Department of Veterinary Clinical Studies, University of Glasgow Veterinary School, Bearsden Road, Glasgow G61 1QH, Scotland, UK
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Abstract

The relationship between faecal nematode egg count and the number of adult Telordasagia circumcincta was examined in 508 naturally infected lambs at 6–7 months of age. The relationship was found to be convex and was empirically described by a gamma-type function of the form y = anb e−cn, where n is the number of adult nematodes present and y is the number of nematode eggs per gramme (epg) of faeces. This equation predicted that the peak expected egg count (277 epg) would occur at a worm burden of 2167 adult worms. The absence of a linear relationship between egg counts and worm numbers is consistent with the existence of severe density-dependent constraints on the fecundity of T. circumcincta.

Keywords

Teladorsagia circumcinctanematodesheepfecunditydensity dependence
Type
Research Article
Information
Parasitology , Volume 121 , Issue 4 , October 2000 , pp. 435 - 440
Copyright
2000 Cambridge University Press

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