title: The value of circulating eosinophil count as a selection criteria for resistance of sheep to trichostrongyle parasites.
abstract: In merino sheep bred for either increased or decreased resistance to Haemonchus contortus, faecal worm egg counts (FEC) were lower in the resistant line (6,831 vs 17,645 epg, P < 0.01), and circulating eosinophils (EOS) were higher, but not significantly so (3.40 x 10(4) ml(-1) vs 1.40 x 10(4) ml(-1), P = 0.1 1). Another flock was artificially infected with Trichostrongylus colubriformis and significant genetic variation was found in both FEC (heritability 0.40 +/- 0.11) and EOS (0.19 +/- 0.08). In a third flock comprising tropical sheep breeds, a natural challenge with T. colubriformis resulted in significant sire effects on FEC (heritability 0.20 +/- 0.10) but not EOS (heritability inestimable). We conclude that EOS offers no advantage over FEC as it selection criterion for resistance.
authors.affiliation: CSIRO Division of Animal Production, PMB Armidale, NSW, Australia.
authors.forename: R R
authors.initials: RR
authors.lastname: Woolaston
authors.forename: P
authors.initials: P
authors.lastname: Manueli
authors.forename: S J
authors.initials: SJ
authors.lastname: Eady
authors.forename: I A
authors.initials: IA
authors.lastname: Barger
authors.forename: L F
authors.initials: LF
authors.lastname: Le Jambre
authors.forename: D J
authors.initials: DJ
authors.lastname: Banks
authors.forename: R G
authors.initials: RG
authors.lastname: Windon
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004804:Eosinophils; D005260:Female; D006188:Haemonchiasis / Q000235:genetics / Q000276:immunology / Q000662:veterinary; D007113:Immunity, Innate / Q000235:genetics; D007958:Leukocyte Count; D008297:Male; D010270:Parasite Egg Count; D011237:Predictive Value of Tests; D012641:Selection, Genetic; D012756:Sheep; D012757:Sheep Diseases / Q000235:genetics / Q000276:immunology*; D014252:Trichostrongyloidiasis / Q000235:genetics / Q000276:immunology / Q000662:veterinary*; D014253:Trichostrongylosis / Q000235:genetics / Q000276:immunology / Q000662:veterinary