The relationship between faecal nematode egg count and the number of adult
Telordasagia circumcinctawas 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 be− cn, where nis the number of adult nematodes present and yis 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.