The genetic basis for the selection of dairy goats with enhanced resistance to gastrointestinal nematodes.

Felix Heckendorn,Steffen Werne,Chris Stricker,Veronika Maurer,Anastasios Saratsis,Anna Bieber

doi:10.1051/parasite/2017033

Felix Heckendorn, Steffen Werne + Show 4 more

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https://doi.org/10.1051/parasite/2017033

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Abstract

Gastrointestinal nematodes (GIN) severely affect small ruminant production worldwide. Increasing problems of anthelmintic resistance have given strong impetus to the search for alternative strategies to control GIN. Selection of animals with an enhanced resistance to GIN has been shown to be successful in sheep. In goats, the corresponding information is comparatively poor. Therefore, the present study was designed to provide reliable data on heritabilities of and genetic correlations between phenotypic traits linked to GIN and milk yield in two major dairy goat breeds (Alpine and Saanen). In all, 20 herds totalling 1303 goats were enrolled in the study. All herds had (i) a history of gastrointestinal nematode infection, (ii) uniform GIN exposure on pasture and (iii) regular milk recordings. For all goats, individual recordings of faecal egg counts (FEC), FAMACHA© eye score, packed cell volume (PCV) and milk yield were performed twice a year with an anthelmintic treatment in between. The collected phenotypic data were multivariately modelled using animal as a random effect with its covariance structure inferred from the pedigree, enabling estimation of the heritabilities of the respective traits and the genetic correlation between them. The heritabilities of FEC, FAMACHA© and PCV were 0.07, 0.22 and 0.22, respectively. The genetic correlation between FEC and FAMACHA© was close to zero and −0.41 between FEC and PCV. The phenotypic correlation between FEC and milk yield was close to zero, whereas the genetic correlation was 0.49. Our data suggest low heritability of FEC in Saanen and Alpine goats and an unfavourable genetic correlation of FEC with milk yield.

Highlights

Gastrointestinal parasitism is one of the most important diseases of ruminant livestock, affecting pasture-based production systems worldwide [38]
H. contortus was most prevalent in our trial, whereas Trichostrongylus spp. and Teladorsagia spp. were the main Gastrointestinal nematodes (GIN) species in Morris’s study. This could partly explain the pronounced positive correlation found in our study and is further substantiated by the fact that the genetic correlation between faecal egg counts (FEC) specific to H. contortus and test day milk yield in our study was stronger than for overall FEC
Another possibility to explain the discrepancy in results between our study and the work by Morris et al relates to potential differences in pasture infection pressure with GIN

Summary

Introduction

Gastrointestinal parasitism is one of the most important diseases of ruminant livestock, affecting pasture-based production systems worldwide [38]. The control of gastrointestinal nematodes (GIN) relied essentially on the repeated use of anthelmintics. Amongst other factors, this practice has led to a rapid evolution of anthelmintic resistance in goats [40, 44, 54]) and sheep [25, 46]. The scientific community today largely agrees that the control of GIN depending solely on anthelmintics is not sustainable [30, 42]. This situation was and still is a strong driver of the search for more sustainable strategies to control GIN, either by reducing the use of anthelmintics to slow down the process of resistance development, or by trying to replace them completely. In situations where Haemonchus spp. are the dominant GIN species, packed cell volume (PCV) and FAMACHAÓ eye scores have been shown to be good selection traits [4, 32, 51]

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