Evidence for multiple anthelmintic resistance has emerged rapidly. The need to investigate innovative alternatives to maximise nematode control is significantly more critical. Selection of sheep with above average natural or acquired resistance to infection is one such option that is being studied. Progeny testing for faecal nematode egg count (FEC) has been evaluated following natural infection. Research involving 104 sires used on 4 commercial Romney studies over the last 2-5 years demonstrated considerable genetic variation. Heritability estimates for FEC ranged from 0.17 to 0.27. Moderate to strong positive genetic correlations (0.38-0.75) between FEC1 and FEC2 were observed. Furthermore, genetic correlations between FEC1 or FEC2 and production traits, including weaning weight, later liveweights and fleece weight were moderate. Breeders face a philosophical dilemma whether to become involved in selection for nematode resistance or not in the face of the many unanswered questions, including why and how to undertake the work. Results to date indicate that breeders can adopt and apply a screening protocol to add to breeding trait records.
Proceedings of the New Zealand Society of Animal Production, Volume 53, , 311-314, 1993
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