Selection for yearling fleece weight and its effect on fleece shedding in New Zealand Wiltshire sheep

O’Connell, D.; Scobie, D. R.; Hickey, S. M.; Sumner, R. M. W.; Pearson, A. J.

doi:10.1071/an11281

Cited by 13 publications

(19 citation statements)

References 10 publications

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“…In other crossbred populations, sex only appeared to have a slight effect on WS (Pollott, ). However, O'Connell, Scobie, Hickey, Sumner, and Pearson () reported an effect of sex and selection line (similar to contemporary group in our study) on fleece shedding in yearling Wiltshire Horn sheep, which was not observed in lamb fleece shedding. The number of lambs born and reared also had an effect on WS (

P < 0.001

) while age did not (

P = 0.99

), which may be due to the variability in WS (Figure ).…”

Section: Resultssupporting

confidence: 70%

See 1 more Smart Citation

Lamb wool shedding is a good predictor of ewe wool shedding

Jurado

Kuehn

Lewis

2019

J Animal Breeding Genetics

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Interest in reducing labour costs due to shearing has led to development of breed types that shed their wool naturally. Selection at young ages can facilitate response. Reliability of predictions of adult from lamb wool shedding (WS) is thus key in the design of breeding programmes to increase shedding. Our objectives were to estimate heritabilities and genetic relationships between WS measured once in lambs and repeatedly in ewes and to assess the accuracy of lamb WS EBV to predict ewe WS EBV based on a multi‐trait threshold or a repeatability model. Data were 4,971 lamb and 3,335 ewe WS records on a Romanov, White Dorper and Katahdin composite flock. For the multivariate model, WS heritability ranged from 0.47 ± 0.03 in lambs to 0.59 ± 0.04 at 1 year of age. For the repeatability model, WS in adult ewes was moderately heritable (0.50 ± 0.03) and repeatable (0.60 ± 0.02). Genetic correlations were 0.72 ± 0.04, 0.65 ± 0.05, 0.50 ± 0.09 and 0.51 ± 0.09 between lamb WS and 1st through 4th record, respectively. Given the moderately high heritability and high correlations between WS performance in lambs and ewes, selecting animals early in life would effectively increase WS in crossbred flocks.

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P < 0.001

) while age did not (

P = 0.99

), which may be due to the variability in WS (Figure ).…”

Section: Resultssupporting

confidence: 70%

“…The repeatability of WS was

0.60 \pm 0.02

, which was lower than the value of

0.77 \pm 0.01

reported by O'Connell et al () in a New Zealand Wiltshire Horn sheep flock. Permanent environmental effect therefore appears to play a small role, accounting for approximately a 10 per cent of the variation in WS.…”

Section: Resultscontrasting

confidence: 65%

Lamb wool shedding is a good predictor of ewe wool shedding

Jurado

Kuehn

Lewis

2019

J Animal Breeding Genetics

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“…Interestingly, the Wiltshire individuals were sampled from a New Zealand flock that experienced several strong and successive bottlenecks in its recent history. Indeed, its founders were imported in 1974 from Australia where the breed had previously been introduced in 1952 and survived as a remnant population of as few as 12 ewes (O'Connell, Scobie, Hickey, Sumner, & Pearson, ). Assuming a generation time of approximately 4 years in sheep, the distribution of the contribution of the most recent classes to the overall inbreeding is thus consistent with this demographic history.…”

Section: Resultsmentioning

confidence: 99%

A model‐based approach to characterize individual inbreeding at both global and local genomic scales

2017

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Inbreeding results from the mating of related individuals and may be associated with reduced fitness because it brings together deleterious variants in one individual. In general, inbreeding is estimated with respect to an arbitrary base population consisting of ancestors that are assumed unrelated. We herein propose a model-based approach to estimate and characterize individual inbreeding at both global and local genomic scales by assuming the individual genome is a mosaic of homozygous-by-descent (HBD) and non-HBD segments. The HBD segments may originate from ancestors tracing back to different periods in the past defining distinct age-related classes. The lengths of the HBD segments are exponentially distributed with class-specific parameters reflecting that inbreeding of older origin generates on average shorter stretches of observed homozygous markers. The model is implemented in a hidden Markov model framework that uses marker allele frequencies, genetic distances, genotyping error rates and the sequences of observed genotypes. Note that genotyping errors, low-fold sequencing or genotype-by-sequencing data are easily accommodated under this framework. Based on simulations under the inference model, we show that the genomewide inbreeding coefficients and the parameters of the model are accurately estimated. In addition, when several inbreeding classes are simulated, the model captures them if their ages are sufficiently different. Complementary analyses, either on data sets simulated under more realistic models or on human, dog and sheep real data, illustrate the range of applications of the approach and how it can reveal recent demographic histories among populations (e.g., very recent bottlenecks or founder effects). The method also allows to clearly identify individuals resulting from extreme consanguineous matings.

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“…Interestingly, the Wiltshire individuals were sampled from a New-Zealand flock that experienced several strong and successive bottlenecks in its recent history. Indeed, its founders were imported in 1974 from Australia where the breed had previously been introduced in 1952 and survived as a remnant population of as few as 12 ewes (O’Connell et al , 2012). Assuming a generation time of approximately 4 years in sheep, the distribution of the contribution of the most recent classes to the overall inbreeding is thus consistent with this demographic history.…”

Section: Resultsmentioning

confidence: 99%

A whole-genome-based approach for estimation and characterization of individual inbreeding

Druet

Gautier

2017

Preprint

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1Inbreeding results from the mating of related individuals and has negative consequence because it brings together 2 deleterious variants in one individual. Inbreeding is associated with recessive diseases and reduced production or 3 fitness. In general, inbreeding is estimated with respect to a base population that needs to be defined. Ancestors 4 in generations anterior to the base population are considered unrelated. We herein propose a model that estimates 5 inbreeding relative to multiple age-based classes. Each inbreeding distribution is associated to a different time in 6 the past: recent inbreeding generating longer homozygous streches than more ancient. Our model is a mixture of 7 exponential distribution implemented in a hidden Markov model framework that uses marker allele frequencies, 8 genetic distances, genotyping error rates and the sequences of observed genotypes. Based on simulations studies, 9 we show that the inbreeding coefficients and the age of inbreeding are correctly estimated. Mean absolute errors 10 of estimators are low, the efficiency depending on the available information. When several inbreeding classes 11 are simulated, the model captures them if their ages are sufficiently different. Genotyping errors or low-fold 12 sequencing data are easily accommodated in the hidden Markov model framework. Application to real data sets 13 illustrate that the method can reveal different demographic histories among populations, some of them presenting 14 very recent bottlenecks or founder effects. The method also clearly identifies individuals resulting from extreme 15 consanguineous matings. 16With his pioneering work on self-fertilization, Darwin early noticed that mating relatives generally leads to off-18 spring with a reduced fitness (Darwin, 1876). This phenomenon now referred to as inbreeding depression may 19 mostly result from an increased homozygosity for (recessive) deleterious variants although a lack of heterozygos-20 ity at loci displaying heterozygous advantage (overdominance) might also be involved (Charlesworth and Willis, 21 2009). Accordingly, populations displaying high levels of individual inbreeding show a higher prevalence of mono-22 genic disorders (e.g., Charlier et al., 2008) or complex diseases (e.g., Rudan et al., 2003). Inbreeding depression 23 can thus increase the risk of extinction by reducing the population growth rate (Hedrick and Kalinowski, 2000; 24 Keller and Waller, 2002) although it may be conversely favorable in some conditions by purging deleterious vari-25 ants from the population (Estoup et al., 2016). Assessing individual inbreeding is then of paramount interest to 26 improve the management of populations under conservation or selection, and from a more general evolutionary 27 perspective to better understand the genetic architecture of inbreeding depression. 28The first standard measure for the level of individual inbreeding was introduced by Wright (1922) as the 29 coefficient of inbreeding (F) that he defined in terms of correlations betwe...

show abstract

Selection for yearling fleece weight and its effect on fleece shedding in New Zealand Wiltshire sheep

Cited by 13 publications

References 10 publications

Lamb wool shedding is a good predictor of ewe wool shedding

Lamb wool shedding is a good predictor of ewe wool shedding

A model‐based approach to characterize individual inbreeding at both global and local genomic scales

A whole-genome-based approach for estimation and characterization of individual inbreeding

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