Genetic and Phenotypic Parameter Estimates of Total and Partial Lifetime Traits for Dairy Ewes

El-Saied, U.M.; Fuente, L. F. de la; Carriedo, J.A.; Primitivo, F. San

doi:10.3168/jds.s0022-0302(05)73009-5

Cited by 19 publications

(15 citation statements)

References 19 publications

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“…El-Saied et al (2005) (Brash et al, 1994) and 0.08 for Scottish Blackface (Conington et al, 2001)]. The heritability estimated for functional longevity in this study was higher than estimates reported by Chirinos et al (2007) in cattle, ranging between 0.05 and 0.07, whereas Neerhof et al (2000) and Ducrocq and Sölkner (1998b) reported heritabilities around 0.05 for the logarithmic scale and 0.22 for the real scale.…”

Section: Discussioncontrasting

confidence: 51%

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Effect of somatic cell count level on functional longevity in Valle del Belice dairy sheep assessed using survival analysis

Riggio

Maizon

Portolano

et al. 2009

Journal of Dairy Science

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The objectives of this study were to evaluate the effect of somatic cell count (SCC) on functional longevity and to estimate the heritability of functional longevity using survival analysis in Valle del Belice dairy sheep. A total of 4,880 lactations of 2,190 ewes from 11 flocks were used. In this study, SCC was considered as an indication of subclinical mastitis. In case of clinical cases, identified by the technicians at milking time, test-day weights and milk samples of those ewes were not considered. Somatic cells were analyzed as counts, without any transformation, and were grouped in 3 classes based on the observed SCC maximum (mxSCC). The mxSCC classes, expressed as 10 3 cells/mL, were classified as 1 if mxSCC ≤ 500, 2 if 500 < mxSCC < 1,000, and 3 if mx-SCC ≥ 1,000. An increase in SCC was associated with an increased hazard of being culled. Ewes in the highest class of SCC on a test-day had a 20% higher hazard of being culled than those in the lowest class. Therefore, SCC played a role in culling decisions of Valle del Belice dairy sheep farmers. The heritability estimate for functional longevity was 7% on the logarithmic scale and 11% on the real scale, indicating that selection for this trait is possible in sheep. The flock-year-season effect explained 19% of the variation on the logarithmic scale and 27% of the variation on the real scale.

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Section: Discussioncontrasting

confidence: 51%

“…Longevity corrected for milk production level, functional longevity, is an approximate measure for involuntary culling (Dekkers, 1993). At present, only a few estimates of heritability for longevity are available in dairy sheep (Conington et al, 2001;El-Saied et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Effect of somatic cell count level on functional longevity in Valle del Belice dairy sheep assessed using survival analysis

Riggio

Maizon

Portolano

et al. 2009

Journal of Dairy Science

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“…There are few reports in the literature of genetic parameters for ewe longevity in sheep, and those available generally suggest the trait is lowly heritable. For Churra ewes, estimates of the heritability for longevity ranged from 0.02 to 0.06 (El-Saied et al, 2005). Brash et al (1994) and Conington et al (2001) also reported low heritabilities for ewe longevity at 0.06 and 0.08, respectively, in Australian Dorset and Scottish Blackface sheep.…”

Section: Heritabilities Of Longevity Growth Body Composition Mouthmentioning

confidence: 99%

“…Different approaches are used for genetic evaluation of longevity including survival analysis (Ducrocq et al, 1988;Ducrocq, 1994) and linear models (Kersey DeNise et al, 1987;El-Saied et al, 2005). Survival analysis offers several advantages including use of censored and uncensored records (Vukasinovic et al, 1999;Caraviello et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Genetic relationship between longevity and objectively or subjectively assessed performance traits in sheep using linear censored models1

Mekkawy

Roehe

Lewis

et al. 2009

Journal of Animal Science

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Genetic parameters of longevity in crossbred Mule ewes, and genetic relationships among longevity, growth, body composition, and subjectively assessed traits on Mule lambs and ewes have been estimated using Bayesian linear censored models. Additionally, the genetic associations between longevity and culling reasons were examined. Data comprised 1,797 observations of Mule ewes for longevity, culling reasons, growth, body composition, mouth scores, and type traits. Longevity was defined as the time (in years) from 2 yr of age (the age at first lambing of most ewes) to culling or death. Censored data (i.e., observations for which only the lower bound of the true longevity is known, such as when the animals are still alive) comprised 24% of all observations for longevity. Bivariate analyses were used to analyze the longevity of the ewe with each performance trait by fitting linear Bayesian models considering censored observations. Longevity was split into 3 different sub-traits: age at culling due to teeth/mouth conditions, age at culling due to udder conditions, and age at culling due to other culling reasons. These sub-traits and their aggregation into the overall trait of longevity were analyzed in a multipletrait model. The heritability of longevity was moderate at 0.27, whereas heritabilities of the growth and body composition traits ranged from 0.11 for average of shoulder, loin, and gigot conformation to 0.36 for ewe BW at first premating. Mouth scores and type traits had heritabilities ranging from 0.13 for jaw position to 0.39 for fleece quality. All analyzed traits showed low genetic correlations with longevity, ranging from -0.20 for average conformation scores in live animals to 0.18 for tooth angle. Teeth/mouth conditions resulted in the greatest heritability (0.15) among the sub-traits based on the separate culling reasons. Genetic correlations between separate culling reasons were low to high (0.12 to 0.63 for teeth/mouth conditions with udder conditions and other culling reasons, respectively). Longevity may be preferred as a selection criterion because of (i) its moderate heritability compared with its component sub-traits based on specific culling reasons, and (ii) its moderate to high genetic correlation with these component sub-traits. The moderate heritability for longevity reflects the potential of this trait for genetic improvement, especially when longevity is based on clearly defined culling reasons.

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“…As other lifetime traits in animal species, AFL has a skewed phenotypic distribution with evident over-representation of the right tail, thus discouraging its analysis under standard Gaussian-related mixed linear models (El-Saied et al, 2005). Both the generalization of Gaussian models to non-symmetrical patterns and the implementation of non-linear models on the basis of skew parametric distributions have been suggested in previous studies Casellas and Bach, 2012;García et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Comparison between linear and proportional hazard models for the analysis of age at first lambing in the Ripollesa breed

Casellas

2016

Animal

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Age at first lambing (AFL) plays a key role on the reproductive performance of sheep flocks, although there are no genetic selection programs accounting for this trait in the sheep industry. This could be due to the non-Gaussian distribution pattern of AFL data, which must be properly accounted for by the analytical model. In this manuscript, two different parameterizations were implemented to analyze AFL in the Ripollesa sheep breed, that is, the skew-Gaussian mixed linear model (sGML) and the piecewise Weibull proportional hazards model (PWPH). Data were available from 10 235 ewes born between 1972 and 2013 in 14 purebred Ripollesa flocks located in the north-east region of Spain. On average, ewes gave their first lambing short after their first year and a half of life (590.9 days), and within-flock averages ranged between 523.4 days and 696.6 days. Model fit was compared using the deviance information criterion (DIC; the smaller the DIC statistic, the better the model fit). Model sGML was clearly penalized (DIC = 200 059), whereas model PWPH provided smaller estimates and reached the minimum DIC when one cut point was added to the initial Weibull model (DIC = 132 545). The pure Weibull baseline and parameterizations with two or more cut points were discarded due to larger DIC estimates (>134 200). The only systematic effect influencing AFL was the season of birth, where summer-and fall-born ewes showed a remarkable shortening of their AFL, whereas neither birth type nor birth weight had a relevant impact on this reproductive trait. On the other hand, heritability on the original scale derived from model PWPH was high, with a model estimate place at 0.114 and its highest posterior density region ranging from 0.079 and 0.143. As conclusion, Gaussian-related mixed linear models should be avoided when analyzing AFL, whereas model PWPH must be viewed as better alternative with superior goodness of fit; moreover, the additive genetic background underlying this reproductive trait supports its inclusion into current genetic selection programs given its economic importance.

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Genetic and Phenotypic Parameter Estimates of Total and Partial Lifetime Traits for Dairy Ewes

Cited by 19 publications

References 19 publications

Effect of somatic cell count level on functional longevity in Valle del Belice dairy sheep assessed using survival analysis

Effect of somatic cell count level on functional longevity in Valle del Belice dairy sheep assessed using survival analysis

Genetic relationship between longevity and objectively or subjectively assessed performance traits in sheep using linear censored models1

Comparison between linear and proportional hazard models for the analysis of age at first lambing in the Ripollesa breed

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