Studies on Ascaridia galli in chickens kept at different stocking rates

The development of Ascaridia galli infections was investigated over a period of 378 days in parasite naive chicken flocks ('permanent flocks') kept at different stocking rates and infected by introducing previously infected chickens (seeder birds). The results of this study indicated that differences in stocking rate may lead to different levels of establishment of A. galli infections in chickens. Furthermore, significantly higher weight gains were seen in the medium stocking rate (MSR) group than in either the low stocking rate (LSR) or the high stocking rate (HSR) groups. Periodically, the egg excretion was significantly different between the groups. Although not significant for the whole period, the general trend was that the egg excretion was lower in the MSR group than the LSR and HSR groups. The mean worm burdens in the permanent flocks at the end of the experiment were not significantly different from each other. To estimate the availability of infective eggs in the houses and pens, tracer animals were introduced into each of the permanent flocks every month. Information derived from tracer animals did not confirm an effect of stocking rate on the availability of infective eggs in the environment, although there was a trend towards higher mean worm burdens in the tracers from the MSR group.