Measurement of phenotypic resilience to gastro-intestinal nematodes in Merino sheep and association with resistance and production variables

Kelly, Gareth Andrew; Kahn, Lewis; Walkden‐Brown, Stephen W.

doi:10.1016/j.vetpar.2012.12.018

Cited by 15 publications

(8 citation statements)

References 20 publications

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“…Joint selection for productivity and WEC also leads to animals being selected to be resistant to the consequences of infection, referred to as resilience. One way to measure resilience is to measure growth under worm challenge (Kelly, Kahn, & Walkden‐Brown, ). Both resistance and resilience are important traits and are likely to be correlated, but also affect WEC via the environment, as excretion of eggs onto the pasture increases the average worm burden, which in turn increases the chance of (re‐)infection within a flock (Bishop, ).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of the breeding values for growth rate and worm egg count to environmental worm burden in Australian Merino sheep

Hollema

Bijma

Werf

2018

J Animal Breeding Genetics

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The objective of this study was to explore the sensitivity of breeding values for growth rate and worm egg count (WEC, cube root transformed) to environmental worm burden, measured as the average WEC for each contemporary group (CGWEC). Growth rate and WEC were measured on 7,818 naturally infected Merino lambs in eight flocks across Australia, linked through common use of AI sires. Through bivariate analysis, genetic correlations of 0.55 ± 0.23 and 0.30 ± 0.16 were found for growth rate and WEC between low and high CGWEC, respectively. In a second analysis, breeding values for growth rate and WEC were regressed on CGWEC with a random regression model. The heritability for growth rate varied from 0.23 to 0.16 from low to high CGWEC, and the heritability for WEC varied from 0.25 to 0.36. Results suggest that breeding values for both growth rate and WEC are sensitive to environmental worm burden. Animals expressed less genetic variation for growth rate and more genetic variation for WEC in high CGWEC than in low CGWEC. This form of genotype-by-environment interaction should therefore be considered in genetic evaluation of both growth rate and WEC, to increase the efficiency of selection for animals that are more parasite resistant and more resilient to environmental worm challenge.

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Section: Introductionmentioning

confidence: 99%

Sensitivity of the breeding values for growth rate and worm egg count to environmental worm burden in Australian Merino sheep

Hollema

Bijma

Werf

2018

J Animal Breeding Genetics

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“…First, it advances our understanding of parasite-mediated selection on hosts, for some of the most prevalent and abundant parasite taxa on Earth [1] . Second, quantifying variation in tolerance may inform management of livestock to enhance productivity during nematode infection [19] – [21] . Third, the quantitative approach to studying variation in nematode tolerance applied here, in a natural animal population, may also prove useful in future studies of how variation in human health with increasing gastrointestinal nematode burdens [1] , [2] , [22] is generated and/or maintained.…”

Section: Introductionmentioning

confidence: 99%

Natural Selection on Individual Variation in Tolerance of Gastrointestinal Nematode Infection

et al. 2014

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“…The rise in FEC in the selective treatment group in January was the result of the presence of animals that were not selected for deworming in December, so they showed high FEC indicating the possible existence of resilient animals in the flock (Kelly et al 2013). This is indicative of one of the major advantages of selective treatment, namely maintaining a population in refugia which will contribute to prolong the efficacy of drugs (Kenyon and Jackson 2012).…”

Section: Discussionmentioning

confidence: 99%

Effect of selective anthelmintic treatments on health and production parameters in Pelibuey ewes during lactation

Arece-García

López-Leyva

González-Gardúño

et al. 2015

Trop Anim Health Prod

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A study was conducted from December to April 2013, with the aim of evaluating a system of selective antiparasitic treatments using the FAMACHA© color chart compared with a conventional suppressive deworming system every 30 days in Pelibuey ewes during lactation. For the study, 54 ewes were used. They were randomly divided into two groups: FAMACHA and chemical treatments. The ewes in the first group received selective treatment depending on the ocular mucosa coloration (FAMACHA) and body condition score (BCS), while in the second group (chemical) all the animals remained under routine deworming every 30 days. Fecal nematode egg counts, proportion of third-stage trichostrongylid larvae, body condition, coloration of the ocular mucosa, and packed cell volume in the ewes were determined, while in lambs only body weight (BW) was recorded. No significant differences (p > 0.05) were observed in any of the studied variables between groups; however, the use of antiparasitic drugs was reduced during the experimental period in the FAMACHA group and no deaths of lambs or ewes were recorded. The results indicate that during the lactation of ewes, a strategy of selective treatments can be implemented without showing deterioration in major health and productive parameters of these animals.

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Measurement of phenotypic resilience to gastro-intestinal nematodes in Merino sheep and association with resistance and production variables

Cited by 15 publications

References 20 publications

Sensitivity of the breeding values for growth rate and worm egg count to environmental worm burden in Australian Merino sheep

Sensitivity of the breeding values for growth rate and worm egg count to environmental worm burden in Australian Merino sheep

Natural Selection on Individual Variation in Tolerance of Gastrointestinal Nematode Infection

Effect of selective anthelmintic treatments on health and production parameters in Pelibuey ewes during lactation

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