Reproductive performance and genetic parameters for Australian Dorset Sheep

Brash, LD; Fogarty, NM; Gilmour, AR

doi:10.1071/ar9940427

Cited by 30 publications

(15 citation statements)

References 14 publications

(32 reference statements)

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“…The general trends in ewe reproduction with an increase in age were consistent with those reported by Fourie & Heydenrych (1983a), Brash et al (1994a) and Cloete et al (2003). The H line had an advantage (P < 0.01) relative to the L line with regard to lamb output, as was reported previously (Cloete & Scholtz, 1998;Cloete et al, 2003).…”

Section: Discussionsupporting

confidence: 80%

“…The h² estimate for number of lambs born per ewe in Table 3 accorded with estimates in the literature (0.06 - Brash et al, 1994a;0.03 -Brash et al, 1994b;0.07 to 0.12 -Bromley et al, 2000;0.06 to 0.10 -Cloete et al, 2002b;. In the case of number of lambs weaned per ewe, h² was estimated at 0.05.…”

Section: Discussionsupporting

confidence: 76%

“…In the case of number of lambs weaned per ewe, h² was estimated at 0.05. Comparable estimates in the literature were 0.06 (Brash et al, 1994a), 0.03 (Brash et al, 1994b), 0.03 to 0.07 (Bromley et al, 2000); 0.04 (Swan et al, 2001) and 0.04 (Cloete et al, 2002b;. Our estimate for total weight of lamb weaned per ewe (0.05) accorded with those of Bromley et al (2001), ranging from 0.02 to 0.11.…”

Section: Discussionsupporting

confidence: 75%

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Age trends in economically important traits of Merino ewes subjected to 10 years of divergent selection for multiple rearing ability

Cloete¹,

Gilmour²,

Olivier³

et al. 2003

SA J. An. Sci.

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Data were recorded for annual reproduction, wool traits and pre-joining live weight of between 992 (for staple strength) to approximately 1200 production records of Merino ewes over the period from 1997 to 2002. The resource population has been divergently selected from the same base since 1986, either for (H line) or against (L line) maternal multiple rearing ability. When expressed relative to mean L line performance, the advantage in reproduction for the H line amounted to 34% for number of lambs born per ewe, 49% for number of lambs weaned per ewe and 56% for weight of lamb weaned per ewe. Overall trends in reproduction with an increase in age from 2 -7+ years were consistent with corresponding trends in the literature. The shape of these curves did not differ between selection lines, i.e. no significant interaction between selection line and ewe age was found. Maiden H line ewes were heavier than L line contemporaries. Ewe joining weight increased with age in both lines. Line differences were reduced to a tendency in 3-year old ewes, and no subsequent line differences were found. The random non-linear component of the spline for ewe age also interacted with selection line for clean fleece weight. Conclusive advantages in favour of L line ewes were obtained at 3 -6 years of age. In maiden ewes the line difference was restricted to a tendency in favour of the L line while no line difference occurred in 7-year old ewes. Ewes in the L line outperformed H line contemporaries for staple strength at four years of age, but no line difference was found at other ages. Coefficient of variation of fibre diameter and mean fibre diameter did not differ between lines. Coefficient of variation of fibre diameter generally declined curvi-linearly with an increase in ewe age, while fibre diameter showed a near linear increase. Estimates of h² for reproduction traits were 0.09±0.05 for number of lambs born per ewe, 0.05±0.05 for number of lambs weaned per ewe, and 0.05±0.05 for weight of lamb weaned per ewe. Corresponding h² estimates for wool traits were 0.34±0.08 for clean fleece weight, 0.05±0.05 for staple strength, 0.74±0.02 for coefficient of variation and 0.76±0.02 for fibre diameter. A h² estimate of 0.37±0.09 was obtained for ewe live weight at joining. Ewe permanent environment (c² ewe ) for the reproduction traits were 0.15±0.05 for number of lambs born per ewe, 0.19±0.05 for number of lambs weaned per ewe and 0.19±0.05 for weight of lamb weaned per ewe. The corresponding c² ewe estimate for ewe joining weight was 0.40±0.09, while those for annual wool production traits were 0.31±0.08 for clean fleece weight and 0.12±0.05 for staple strength. Coefficient of variation and mean fibre diameter were not influenced by the ewe permanent environment. Line differences in age trends for wool traits and ewe joining weight were attributed to the drainage by reproduction on the reserves of H line ewes. _____________________________________________________________________________________

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Section: Discussionsupporting

confidence: 80%

Section: Discussionsupporting

confidence: 76%

Section: Discussionsupporting

confidence: 75%

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Age trends in economically important traits of Merino ewes subjected to 10 years of divergent selection for multiple rearing ability

Cloete¹,

Gilmour²,

Olivier³

et al. 2003

SA J. An. Sci.

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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%

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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“…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%

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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Reproductive performance and genetic parameters for Australian Dorset Sheep

Cited by 30 publications

References 14 publications

Age trends in economically important traits of Merino ewes subjected to 10 years of divergent selection for multiple rearing ability

Age trends in economically important traits of Merino ewes subjected to 10 years of divergent selection for multiple rearing ability

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

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