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 previo usly infected chickens (seeder birds). The results of this study indic ated that differences in stocking rate may lead to different levels of establishment of A. galli infections in chickens. Furthermore, signif icantly higher weight gains were seen in the medium stocking rate (MSR ) group than in either the low stocking rate (LSR) or the high stockin g 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 pe rmanent flocks at the end of the experiment were not significantly dif ferent from each other. To estimate the availability of infective eggs in the houses and pens, tracer animals were introduced into each of t he permanent flocks every month, Information derived from tracer anima ls did not confirm an effect of stocking rate on the availability of i nfective eggs in the environment, although there was a trend towards h igher mean worm burdens hi the tracers from the MSR group.