Genetics of disease resistance in sheep and goats

Bishop, Stephen; Morris, C. A.

doi:10.1016/j.smallrumres.2007.01.006

Cited by 200 publications

(155 citation statements)

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“…The distribution of marker effects and subsequent lack of experimental power could explain, in part, the inconsistencies between results for linkage analyses in the literature (Dominik, 2005 ;Sayers & Sweeney, 2005 ;Bishop & Morris, 2007). Assuming that many past experiments were underpowered to detect the largest effects estimated here, the proportion of true markers identified reduces and the results become almost impossible to reproduce in (similarly underpowered) subsequent experiments.…”

Section: Discussionmentioning

confidence: 89%

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The distribution of SNP marker effects for faecal worm egg count in sheep, and the feasibility of using these markers to predict genetic merit for resistance to worm infections

et al. 2011

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SummaryGenetic resistance to gastrointestinal worms is a complex trait of great importance in both livestock and humans. In order to gain insights into the genetic architecture of this trait, a mixed breed population of sheep was artificially infected with Trichostrongylus colubriformis (n=3326) and then Haemonchus contortus (n=2669) to measure faecal worm egg count (WEC). The population was genotyped with the Illumina OvineSNP50 BeadChip and 48 640 single nucleotide polymorphism (SNP) markers passed the quality controls. An independent population of 316 sires of mixed breeds with accurate estimated breeding values for WEC were genotyped for the same SNP to assess the results obtained from the first population. We used principal components from the genomic relationship matrix among genotyped individuals to account for population stratification, and a novel approach to directly account for the sampling error associated with each SNP marker regression. The largest marker effects were estimated to explain an average of 0 . 48% (T. colubriformis) or 0 . 08 % (H. contortus) of the phenotypic variance in WEC. These effects are small but consistent with results from other complex traits. We also demonstrated that methods which use all markers simultaneously can successfully predict genetic merit for resistance to worms, despite the small effects of individual markers. Correlations of genomic predictions with breeding values of the industry sires reached a maximum of 0 . 32. We estimate that effective across-breed predictions of genetic merit with multi-breed populations will require an average marker spacing of approximately 10 kbp.

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Section: Discussionmentioning

confidence: 89%

“…Genetic variation in resistance to internal parasites has been demonstrated in numerous species, including humans and several livestock species (Kloosterman et al, 1992 ;Quinnell, 2003;Bishop & Morris, 2007). However, the genetic architecture underlying such traits is poorly understood.…”

Section: Introductionmentioning

confidence: 99%

The distribution of SNP marker effects for faecal worm egg count in sheep, and the feasibility of using these markers to predict genetic merit for resistance to worm infections

et al. 2011

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“…Resistance is the ability of the host to moderate the pathogen or parasite life cycle, that is, maintenance of low faecal egg count (FEC) under GINs challenge. Occasionally, 'tolerance' is used to explain a host's ability to resist the pathogenic consequences of infection (Bishop and Morris, 2007), which is more related to resilience. Resilience is the ability of animals to uphold performance in the face of a -E-mail: abubaker_79@yahoo.com disease challenge, that is, to resist anaemia irrespective of FEC of blood-sucking parasites (Bishop and Morris, 2007;Burke and Miller, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Occasionally, 'tolerance' is used to explain a host's ability to resist the pathogenic consequences of infection (Bishop and Morris, 2007), which is more related to resilience. Resilience is the ability of animals to uphold performance in the face of a -E-mail: abubaker_79@yahoo.com disease challenge, that is, to resist anaemia irrespective of FEC of blood-sucking parasites (Bishop and Morris, 2007;Burke and Miller, 2008). A major difference between resistance and resilience is that the extent of parasite resistance is based on FEC and worm load while resilience is associated with changes in packed cell volume (PCV) and body weight (Chiejina et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Markers/parameters for the evaluation of natural resistance status of small ruminants against gastrointestinal nematodes

Saddiqi¹,

Sarwar

Iqbal

et al. 2012

Animal

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The high prevalence of anthelmintic-resistant gastrointestinal nematodes (GINs) throughout the world has led to the need for alternative worm control strategies. One of the possible substitutes to reduce the problems of drug resistance and residue is the evaluation/breeding of small ruminants for greater resistance to the GINs (organically produced), which in turn would be a helpful tool to predict the performance of an animal. At present, the existing diversity in the genetic potential to resist/tolerate GINs infection both within and between breeds has been validated. Successful selection of animals to define the genotype and identified resistance is related to the employed markers. A number of phenotypic traits such as faecal egg count (FEC), worm burden, serum antibodies, peripheral eosinophilia, packed cell volume, live weight, serum protein and albumin concentrations have been used for this purpose both in natural and artificial infections. Relatively resistant/tolerant animals have also been found to have mastocytosis, globule leucocytes, high levels of histamine and immunoglobulin (Ig) A and IgE concentrations. Of these traits, the principal and most practical measurement used to assess resistance status in animals undergoing similar parasite challenges is FEC. FEC has a positive/negative correlation with other biochemical, cellular and immunological parameters; however, the reliability of individual trial is often questioned and valuable information regarding the genetic makeup can be obtained from pooled data of a large number of trials and parameters. This paper covers all the aspects reported in the literature on various parameters considered to evaluate the resistance status of a range of small ruminant breeds.

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“…Molecular genetics found that this resistance depended on the DQA2 gene of the major histocompatibility complex. Today a test for selection at the molecular level is now commercially available allowing the selection without the need to monitor the phenotypic (clinical) expression of the disease in the flock (Hickford et al, 2004;Bishop and Morris, 2007;Mirkena et al, 2010). Second, mastitis is an inflammation of the mammary gland resulting from bacterial infections.…”

Section: Introductionmentioning

confidence: 99%

Minimising pain in farm animals: the 3S approach – ‘Suppress, Substitute, Soothe’

Guatteo

Levionnois

Fournier

et al. 2012

Animal

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Recently, the French National Institute for Agricultural Research appointed an expert committee to review the issue of pain in food-producing farm animals. To minimise pain, the authors developed a ‘3S’ approach accounting for ‘Suppress, Substitute and Soothe’ by analogy with the ‘3Rs’ approach of ‘Reduction, Refinement and Replacement’ applied in the context of animal experimentation. Thus, when addressing the matter of pain, the following steps and solutions could be assessed, in the light of their feasibility (technical constraints, logistics and regulations), acceptability (societal and financial aspects) and availability. The first solution is tosuppressany source of pain that brings no obvious advantage to the animals or the producers, as well as sources of pain for which potential benefits are largely exceeded by the negative effects. For instance, tail docking of cattle has recently been eliminated. Genetic selection on the basis of resistance criteria (as e.g. for lameness in cattle and poultry) or reduction of undesirable traits (e.g. boar taint in pigs) may also reduce painful conditions or procedures. The second solution is tosubstitutea technique causing pain by another less-painful method. For example, if dehorning cattle is unavoidable, it is preferable to perform it at a very young age, cauterising the horn bud. Animal management and constraint systems should be designed to reduce the risk for injury and bruising. Lastly, in situations where pain is known to be present, because of animal management procedures such as dehorning or castration, or because of pathology, for example lameness, systemic or local pharmacological treatments should be used tosoothepain. These treatments should take into account the duration of pain, which, in the case of some management procedures or diseases, may persist for longer periods. The administration of pain medication may require the intervention of veterinarians, but exemptions exist where breeders are allowed to use local anaesthesia (e.g. castration and dehorning in Switzerland). Extension of such exemptions, national or European legislation on pain management, or the introduction of animal welfare codes by retailers into their meat products may help further developments. In addition, veterinarians and farmers should be given the necessary tools and information to take into account animal pain in their management decisions.

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Genetics of disease resistance in sheep and goats

Cited by 200 publications

References 70 publications

The distribution of SNP marker effects for faecal worm egg count in sheep, and the feasibility of using these markers to predict genetic merit for resistance to worm infections

The distribution of SNP marker effects for faecal worm egg count in sheep, and the feasibility of using these markers to predict genetic merit for resistance to worm infections

Markers/parameters for the evaluation of natural resistance status of small ruminants against gastrointestinal nematodes

Minimising pain in farm animals: the 3S approach – ‘Suppress, Substitute, Soothe’

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