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

The relationship between faecal nematode egg count and the number of adult Teladorsagia 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 = an(b) 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 2,167 adult worm is consistent with the existence of severe density-dependent constraints on the fecundity of T. circumcincta.