Direct and maternal genetic effects on lamb survival

Burfening, P. J.

doi:10.1016/0921-4488(93)90051-i

Cited by 19 publications

(20 citation statements)

References 24 publications

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“…The maternal genetic effects were more important than the direct genetic effect for viability at birth. Similar findings on the relative contributions of direct and maternal effects on different lamb survival traits were reported by Burfening (1993), Morris et al (2000) and Southey et al (2001). Using a Weibull model, Southey et al (2001) reported an estimate of heritability of 0.20 for lamb survival from birth to 120 days and from 120 to 365 days.…”

Section: Discussionsupporting

confidence: 77%

“…Most studies of lamb survival (e.g. Burfening, 1993;Olivier et al, 1998;Morris et al, 2000) have used cumulative binary data analyses where animals are classified as alive or dead at the end of a period. However, the use of actual survival times through survival analyses enables the discrimination between lambs dying early or late in the period.…”

Section: Introductionmentioning

confidence: 99%

“…Analysis of actual survival time also allows for the use of records from lambs that were culled or died within the period considered due to reasons not related to their viability, such as slaughter or accidental death, which is relatively common under extensive production systems. Estimates of heritability published in the literature for early lamb survival using binary data are mostly small and within the range of 0.00 to 0.09 (Burfening, 1993;Olivier et al, 1998;Matos et al, 2000). In addition, estimates of genetic correlations between survival and weight traits are still lacking in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Analyses of lamb survival of Scottish Blackface sheep

Conington

Brotherstone

et al. 2007

Animal

126

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Scottish Blackface lamb viability records at birth, and postnatal survival from 1 day to 14 days, from 15 days to 120 days and from 121 days to 180 days were used to determine influential factors and to estimate variance components of lamb survival traits. The binary trait viability at birth was analysed using a linear model whereas the postnatal survival traits were analysed as continuous traits using a Weibull model. The data consisted of about 15 000 survival records of lambs born from 1996 to 2005 on two farms in Scotland. The models included fixed factors that had significant effects and random direct and maternal additive genetic effects and maternal litter effects for viability at birth, and sire and maternal litter effects for the postnatal survival traits. The possible effect of maternal behaviour measured around lambing on lamb survival was investigated in separate analyses. Male lambs were found to be at a higher risk of mortality than females during all periods considered. The effect of type of birth and age of dam was more important during the preweaning period than at later ages. The postnatal hazard rate was not significantly affected by the behaviour score of the dams. The genetic merit of dams had more influence on viability at birth than the genetic merit of lambs themselves. Estimates of heritability for postnatal survival traits were in the range of 0.18 to 0.33 and were significantly greater than zero. These results indicate that lamb survival can be improved through farm management practices and genetic selection. Both animal and maternal genetic effects should be considered in breeding programmes for improving viability at birth.

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Section: Discussionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analyses of lamb survival of Scottish Blackface sheep

Conington

Brotherstone

et al. 2007

Animal

126

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“…at a level of two times the corresponding standard error), accords well with literature values which vary between 0.00 and 0.09 (Olivier et al, 1998;Snyman et al, 1998;Cloete et al, 2001;Matika et al, 2003). Lamb survival is a complex trait influenced by the lamb's own ability to survive and by its dam's rearing ability (Burfening, 1993). The temporary environmental (litter) effect was found to be more important in affecting survival of the lamb than the direct genetic and permanent environmental components.…”

Section: Resultssupporting

confidence: 72%

Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Wyk¹,

Fair²,

Cloete³

2004

SA J. An. Sci.

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Genetic parameters for production and reproduction traits in the Elsenburg Dormer sheep stud were estimated using records of 11743 lambs born between 1943 and 2002. An animal model with direct and maternal additive, maternal permanent and temporary environmental effects was fitted for traits considered traits of the lamb (birth and weaning weight and survival). Fixed effects were sex, birth status, year and age of dam. Weaning weights were pre-adjusted to a 100-day equivalent. For reproduction traits (considered as traits of the ewe), which included number and weight of lambs born and weaned, repeatability models were fitted. The random part consisted of direct additive and ewe and sire permanent environmental effects. Direct and maternal heritability estimates were 0.13 and 0.23 for birth weight and 0.07 and 0.09 for weaning weight. Corresponding proportions of total phenotypic variance due to maternal permanent and temporary environment were 0.09 and 0.28 and 0.06 and 0.22 respectively. The genetic correlation between animal effects was -0.23 in the case of birth weight. The results showed that temporary environment (full sibs within a year) generally has a major effect on all pre-weaning traits. The direct heritability estimate of survival was 0.02 while the temporary maternal environmental variance as a proportion of phenotypic variance was 0.10. The estimates obtained for number and weight of lambs born and weaned were generally low, ranging from 0.03 for number of lambs born to 0.11 for total weight at birth. The permanent environmental effect of the ewe accounted for 6-7% of the total phenotypic variance. Genetic correlations of total weight of lamb weaned with the other reproduction traits were generally high (0.64 to 0.92) with low standard errors. The corresponding phenotypic, environmental and ewe permanent environmental correlations were all medium to high and estimated with a fair deal of accuracy according to low standard errors. The genetic relationship between weaning weight of the ewe and her lifetime reproduction (accumulated over four lambing chances) ranged between 0.40 and 0.67. Correlations between number of lambs weaned per ewe and weight of lamb weaned per ewe were particularly high (0.8 -0.9). It was concluded that the maternal environmental effect should be partitioned into two components (permanent and temporary) when data sets involving multiple births over many generations are considered.

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“…Both literature sources concluded that maternal environment contributed most to the repeatability of lamb survival when viewed as a trait of the dam. In the study by Burfening (1993) h² estimates for lamb survival in Rambouillet, Targhee and Columbia sheep ranged from 0.002 to 0.051 on the normal scale. Corresponding m² estimates ranged from 0.052 to 0.112.…”

Section: Discussionmentioning

confidence: 99%

Environmental and genetic aspects of survival and early liveweight in Western Australian Merino sheep

Cloete¹,

Greeff²,

Lewer³

2001

SA J. An. Sci.

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Abstract(Co)variance estimates for birth weight, pre-weaning lamb survival and weaning weight were obtained for Merino lambs derived from 16 bloodlines. Between bloodline variance ratios (± s.e.) amounted to 0.10 ± 0.04 for lamb birth weight, 0.053 ± 0.036 for lamb survival (logit scale) and 0.18 ± 0.07 for lamb weaning weight. Direct additive genetic variances for weaning weight -expressed as a ratio of the total phenotypic variance within bloodlines (h², direct heritability) -were estimated at 0.18 ± 0.02 for birth weight, 0.094 ± 0.020 (logit scale) for pre-weaning survival and 0.30 ± 0.02 for weaning weight. Corresponding maternal genetic variance ratios (m²) were estimated at 0.15 ± 0.02 for birth weight and 0.08 ± 0.02 for weaning weight. It was not significant in the case of lamb survival. Maternal permanent environmental variance ratios (c²) amounted to 0.08 ± 0.02 for birth weight, 0.044 ± 0.018 for lamb survival (logit scale) and 0.07 ± 0.02 for weaning weight. These results were discussed with reference to sheep production.

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Direct and maternal genetic effects on lamb survival

Cited by 19 publications

References 24 publications

Analyses of lamb survival of Scottish Blackface sheep

Analyses of lamb survival of Scottish Blackface sheep

Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Environmental and genetic aspects of survival and early liveweight in Western Australian Merino sheep

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