Comparative genetic resistance to Ascaridia galli infections of 4 different commercial layer-lines.

1. The objective of the study was to compare the establishment and effect of Asaridia galli infections in 4 different layer-lines. 2. A total of 160 birds comprising 4 different commercial layer-lines, ISA Brown, New Hampshire, Skalborg and a cross of New Hampshire(NH) and Skalborg (Sk), were infected with A. galli eggs. The birds were examined for the presence of parasite eggs and parasites at weeks 3, 6 and 9 post infection (pi). 3. At week 6 pi the chickens of the NH line harboured more larvae compared with the three otherlines. The Sk line chickens excreted more A. galli eggs throughout the study compared with the other lines. Female worms in the Sk line were more fecund than the worms in the other lines. Male and female worms recovered from the Sk line at week 9 pi were longer. Male worms recovered from the NH line 6 weeks pi were shorter than male worms from the other lines. Female worms recovered from the NH line were shorter than the female worms from the ISA line and the Sk line. No differences were seen in weight gain among the 4 lines. 4. The results suggest that genetic factors are involved in the establishment and survival of A. galli in the intestine of layers. Further studies are needed to elucidate the genetic mechanisms behind the observed parasitological findings.