Lamb survival in Australian flocks: a review

2014 ◽  
Vol 54 (6) ◽  
pp. 656 ◽  
Author(s):  
G. N. Hinch ◽  
F. Brien
Keyword(s):  
Cold Resistance ◽  
Reproductive Efficiency ◽  
Maternal Behaviour ◽  
The Subject ◽  
Selection For ◽  
Lamb Survival

Lamb survival is known to be a key component of reproductive efficiency in sheep flocks. It has been the subject of a large number of studies over the decades and this review provides an update and insights into the latest understanding of the extent and variability of lamb losses across Australia. The pattern of causes of lamb losses, including dystocia, starvation/exposure, mismothering and predation, are examined. Likewise the importance of birthweight in contributing to such losses is discussed as are strategies for improving lamb survival. The strategies examined include improved ewe nutrition, shelter provision and selection for cold resistance and improved maternal behaviour.

The effects of selection for lean tissue content on maternal and neonatal lamb behaviours in Scottish Blackface sheep

2001 ◽  
Vol 72 (3) ◽  
pp. 555-571 ◽  
Author(s):  
C. M. Dwyer ◽  
A. B. Lawrence ◽  
S. C. Bishop
Keyword(s):  
Genetic Selection ◽  
Maternal Behaviour ◽  
Selection Line ◽  
Median Latency ◽  
Lean Tissue ◽  
Lean Growth ◽  
Tissue Content ◽  
Selection For ◽  
Lamb Survival

AbstractBritish hill sheep are required to give birth to and rear their lambs under harsh extensive conditions. The aim of this study was to investigate whether genetic selection for increased (LEAN) or decreased (FAT) carcass lean content in the Scottish Blackface breed over 7 years had affected the ability of ewes to rear lambs by altering the expression of maternal and neonatal lamb behaviours. The behaviour of 61 ewes (32 LEAN and 29 FAT) and their 119 lambs were recorded at parturition and over the first 8 weeks of life. Overall there were very few effects of selection on the behaviour of the ewes. LEAN ewes were significantly faster than FAT ewes to start grooming their lambs after birth and FAT ewes tended to withdraw more frequently from their lambs than LEAN ewes. There was, however, a highly significant effect of selection line on lamb behaviour. LEAN lambs were significantly quicker than FAT lambs to perform all righting movements (median latency to stand (mins): LEAN = 11·7, FAT = 23·4, P < 0·01), were more likely both to suck (percentage that sucked: LEAN = 81·0%, FAT = 57·1%, P < 0·05), and to play within the first 2 h of birth. The higher rate of sucking in LEAN lambs persisted over the first 3 days after birth (percent observations where lambs were sucking: LEAN = 7·8 (s.e. 0·8), FAT = 5·1 (s.e. 0·6), P < 0·05), when LEAN lambs were also significantly closer to their mothers than FAT lambs. Thereafter, there were no significant effects of ewe or lamb line on behaviours recorded up to 8 weeks after birth. Overall lamb mortality to 8 weeks was 19·3% and was not significantly affected by lamb line. However, lambs that were slow to perform early behaviours had a reduced survival to 8 weeks of age. These data suggest that, although ewe maternal behaviour has not been significantly affected by selection for lean growth, the activity of the neonatal lamb has been affected. Lamb activity was related to lamb survival, even in our indoor lambing conditions. It is likely that the speed with which newborn lambs stand and suck will be even more important for survival under extensive conditions.

A review of the genetic and epigenetic factors affecting lamb survival

2014 ◽  
Vol 54 (6) ◽  
pp. 667 ◽  
Author(s):  
F. D. Brien ◽  
S. W. P. Cloete ◽  
N. M. Fogarty ◽  
J. C. Greeff ◽  
M. L. Hebart ◽  
...  
Keyword(s):  
Direct Selection ◽  
Reproductive Efficiency ◽  
Maternal Behaviour ◽  
Sufficient Information ◽  
Management Options ◽  
Factors Affecting ◽  
Selection Strategies ◽  
Australian Sheep ◽  
Lamb Survival ◽  
Genetic Evaluations

Poor lamb survival pre-weaning is a major source of reproductive inefficiency in Australian sheep flocks. While nutrition and management options have been extensively researched and promoted to improve lamb survival, the present review focuses on the prospects for obtaining genetic gain and helps identify selection strategies for boosting such gains to improve overall reproductive efficiency in the Australian sheep industry. Estimated heritability for lamb survival using linear model analysis is low, although use of threshold models suggests that heritability could be higher, which, if true, could help explain the substantial genetic gains obtained in long-term selection experiments. Epigenetic mechanisms may hinder selection and quantitative trait-loci identification through confounding and/or masking genetic variances and co-variances. With sufficient information, these effects could be considered in genetic evaluations by identifying those components that are amenable to selection. Regarding indirect selection, finding effective criteria for improving lamb survival has proved elusive. Most measures of maternal behaviour, temperament and lambing difficulty researched are poorly correlated genetically with lamb survival. Of lamb behaviours and thermo-genic indicators studied, latency to bleat following handling by humans is moderately genetically correlated with lamb survival, as is neonatal rectal temperature. Industry application remains to be adequately explored for the more promising of these measures. Finally, in lieu of direct selection for lamb survival, there is merit in selecting for multiple-rearing ability or its equivalent, possibly with additional selection criteria for lamb survival and reproductive efficiency.

Maternal behaviour at parturition in outdoor conditions differs only moderately between single-bearing ewes selected for their calm or nervous temperament

2010 ◽  
Vol 50 (7) ◽  
pp. 675 ◽  
Author(s):  
S. L. Bickell ◽  
R. Nowak ◽  
P. Poindron ◽  
D. Ferguson ◽  
D. Blache
Keyword(s):  
Maternal Behaviour ◽  
Human Observer ◽  
Recording Device ◽  
Maternal Experience ◽  
Early Postpartum ◽  
Lower Reactivity ◽  
Extensive Field ◽  
Ewe Lamb ◽  
Selection For ◽  
Lamb Survival

Maternal and lamb behaviours play a major role in lamb survival and there is evidence that selection for calm temperament may help improve lamb survival by improving maternal behaviour. However, the apparent better maternal behaviour of calm ewes might be due partly to their lower reactivity to the presence of the human observer rather than to better maternal behaviour per se. The extent to which the selection for temperament influenced the behaviour of the ewe and lamb after parturition with minimal human disturbance was investigated in the present work. Single-bearing multiparous and primiparous ewes were observed to determine any interactions of temperament with maternal experience on ewe and lamb behaviours. Postpartum ewe-lamb interactions under outdoor lambing conditions were captured by continuous video recordings by a remote controlled recording device for up to 2 h postpartum. Calm ewes licked their lambs more and tended to stay longer on the birth site. Nervous lambs stood up earlier and were quicker to start performing exploratory behaviour. However, duration of suckling during the observation period did not differ between the calm and nervous lambs. There were no effects of maternal experience on the behaviour of the lamb and there were no interactions between temperament and maternal experience on the behaviour of the ewe or lamb. Our study indicates that temperament does influence the early postpartum behaviour of ewes and lambs under extensive field conditions.

Composite trait selection to improve reproduction and ewe productivity: a review

2009 ◽  
Vol 49 (1) ◽  
pp. 9 ◽  
Author(s):  
G. D. Snowder ◽  
N. M. Fogarty
Keyword(s):  
Individual Component ◽  
Genetic Relationships ◽  
Reproductive Efficiency ◽  
Component Trait ◽  
Litter Weight ◽  
Growth Selection ◽  
Component Traits ◽  
Selection For ◽  
Genetic Responses ◽  
Lamb Growth

Reproduction and ewe productivity are complex composite traits that are influenced by several component traits. Genetic improvement by selection for an individual component trait may not always be advantageous because adverse or neutral genetic relationships can exist among the component traits. Selection for an overall composite trait of ewe productivity, defined as litter weight weaned per ewe joined, can result in a balanced biological composite trait with favourable responses in component traits including fertility, number of lambs born, lamb survival, lactation and lamb growth. Selection for litter weight weaned may also overcome adverse genetic relationships among reproductive component traits. This review examines the genetic responses of selecting directly for litter weight weaned, compared with selection responses for one or more of its component traits. It is concluded that selection to improve reproductive efficiency and ewe productivity, under most production and environmental systems, would benefit from selection for a composite trait such as litter weight weaned, rather than for a single component trait.

scholarly journals Gene Selection in Cancer Classification Using Sparse Logistic Regression with L1/2 Regularization

2018 ◽  
Vol 8 (9) ◽  
pp. 1569 ◽  
Author(s):  
Shengbing Wu ◽  
Hongkun Jiang ◽  
Haiwei Shen ◽  
Ziyi Yang
Keyword(s):  
Logistic Regression ◽  
Gene Selection ◽  
Classification Performance ◽  
Cancer Classification ◽  
Sparse Logistic Regression ◽  
The Subject ◽  
Selection For ◽  
Microarray Datasets ◽  
Sparse Methods

In recent years, gene selection for cancer classification based on the expression of a small number of gene biomarkers has been the subject of much research in genetics and molecular biology. The successful identification of gene biomarkers will help in the classification of different types of cancer and improve the prediction accuracy. Recently, regularized logistic regression using the L 1 regularization has been successfully applied in high-dimensional cancer classification to tackle both the estimation of gene coefficients and the simultaneous performance of gene selection. However, the L 1 has a biased gene selection and dose not have the oracle property. To address these problems, we investigate L 1 / 2 regularized logistic regression for gene selection in cancer classification. Experimental results on three DNA microarray datasets demonstrate that our proposed method outperforms other commonly used sparse methods ( L 1 and L E N ) in terms of classification performance.

Opportunities for genetic improvement of lamb survival

2010 ◽  
Vol 50 (12) ◽  
pp. 1017 ◽  
Author(s):  
F. D. Brien ◽  
M. L. Hebart ◽  
D. H. Smith ◽  
J. E. Hocking Edwards ◽  
J. C. Greeff ◽  
...  
Keyword(s):  
Rectal Temperature ◽  
Selection Index ◽  
Genetic Correlations ◽  
Direct Selection ◽  
Reproduction Rate ◽  
Crown Rump Length ◽  
Selection For ◽  
Lamb Survival ◽  
Net Reproduction ◽  
Birth Time

Data on lamb survival and associated traits involving records from 15 192 lambs, 6308 dams and 284 sires from the Sheep CRC’s Information Nucleus were studied. Lamb survival to 3 days of age and to weaning was 85 and 80%, respectively, and heritability (±s.e.) was 0.014 ± 0.010 and 0.010 ± 0.010, respectively. Of the 14 traits recorded at birth, time taken for the lamb to bleat, rectal temperature and crown–rump length had the highest genetic correlations with lamb survival to weaning (–0.43 ± 0.32, 0.56 ± 0.33 and –0.38 ± 0.36, respectively). Under selection for a multi-trait objective including net reproduction rate (but not lamb survival), survival was predicted to decline genetically by 0.25 lambs weaned per 100 lambs born.year, although this was reversed to a gain of 0.20 lambs weaned per 100 lambs born.year by including the trait in the breeding objective and using 50 half-sib and 50 progeny records per selection candidate. Accuracy of selection for lamb survival was improved to 0.735 with a selection index of lamb survival to weaning, lamb ease, birth coat score, time taken to bleat, rectal temperature and crown–rump length, with the addition of 50 half-sibs and 50 progeny records per candidate. Our results suggest that unless actively incorporated into breeding objectives, lamb survival may genetically decline; however, gains are possible with direct selection using half-sib and progeny records. The addition of indirect selection criteria for lamb survival can further improve accuracy, up to 93.4%, but requires further investigation.

scholarly journals Selection for the length of the spermatozoan midpiece in the mouse

1970 ◽  
Vol 16 (3) ◽  
pp. 261-275 ◽  
Author(s):  
D. M. Woolley
Keyword(s):  
Electron Microscope Study ◽  
Selection Response ◽  
Sperm Cells ◽  
Realized Heritability ◽  
Family Selection ◽  
Selected Lines ◽  
Selection Programme ◽  
Proportionate Change ◽  
The Subject ◽  
Selection For

SUMMARYA subcellular dimension, the length of the spermatozoan midpiece, has been the subject of a two-way selection programme in mice. After thirteen generations of within-family selection the divergence between the selected lines amounted to 5·4 phenotypic standard deviations. The realized heritability was found to be 0·76 ± 0·02, dominance and commonenvironmental effects being apparently very small. The reality of the selection response was verified in measurements on live spermatozoa. Other measurements have shown that the change in the length of the midpiece has been independent of its width, and has occurred without a proportionate change in the length of the main-piece of the flagellum. An electron microscope study has shown that the selection has, in fact, brought about changes in the quantity of mitochondrial material in the sperm cells.

Maternal behaviour in Border Leicester, Glen Vale (Border Leicester derived) and Merino sheep

1990 ◽  
Vol 30 (1) ◽  
pp. 27 ◽  
Author(s):  
G Alexander ◽  
D Stevens ◽  
LR Bradley ◽  
SA Barwick
Keyword(s):  
Maternal Care ◽  
Maternal Behaviour ◽  
Selection Program ◽  
Merino Sheep ◽  
Lamb Survival

Ewe and lamb behaviour in traditional Border Leicesters, Glen Vale Border Leicesters of the NSW Agriculture and Fisheries, Glen Vale x Border Leicester crosses and medium-fine-wool Merinos, all running in paddocks of 3-4.5 ha, were compared in spring 1983 at Glen Innes, N.S.W. Twenty-eight aspects of behaviour with a known or reputed influence on lamb survival, especially of multiples, were examined in undisturbed and contrived situations. The Glen Vales and their crosses were superior to the Border Leicesters and Merinos in behaviour and lamb survival, particularly behaviour concerned with the ability of ewes to keep their lambs together. The study indicates that contrived twin-care tests could form the basis of a selection program to improve maternal care and survival of multiples.

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