Effect and repeatability of Ascaridia galli egg output in cockerels following a single low dose infection

Three groups of caged 20 Tetra-SL cockerels aged 1 day were orally infected with 30, 60 or 125 embryonated Ascaridia galli eggs. After 11, 12 and 13 w eeks, faecal egg counts (FECs) were determined. All birds were slaughtered after the last sampling. A group of 25 control birds was sampled and slaugh tered in parallel. The gastrointestinal tracts were examined for the presen ce of adult stages of A. galli. A random sample of 10% was also examined fo r the presence of immature stages of A, galli. The group with an infection dose of 125 eggs showed the highest average worm burden (p < 0.05) and numb er of females (p < 0.05), but the mean establishment rate was the lowest in this group. There was no significant difference in the mean log FEC betwee n the groups. The log FEC per female worm was the highest in the low infect ion group (p < 0.05). The average worm length and weight and the birds body weight were not significantly different among the groups. The estimated re peatabilities for mean log FEC of the different samples were reasonably hig h (0.55-0.87). This may open a way of genetic selection for A, galli resist ance in chickens, which will be of importance for birds kept in alternative and organic farming systems. (C) 2001 Elsevier Science B.V. All rights res erved.