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Chronic stress in sheep: assessment tools and their use in different management conditions
- CM Dwyer, HLI Bornett
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- Journal:
- Animal Welfare / Volume 13 / Issue 3 / August 2004
- Published online by Cambridge University Press:
- 11 January 2023, pp. 293-304
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Chronic stress occurs when animals are unable to deal with a persistent stressor with species-typical responses, or when several stressors are present concurrently. Chronic stress is most frequently considered in intensive systems, but it may also be a welfare concern for extensively managed species, such as the sheep. Here we review behavioural and physiological responses of sheep to experimentally induced chronic stressors to determine relevant indicators of chronic stress. Neuroendocrine responses to chronic stress are difficult to interpret because initial responses are followed by an apparent normalisation. Thus, cortisol or catecholamines may be at or below pre-stress levels during chronic stress, but this varies with different stressors. Chronic stress can also affect reproductive function, impair body and wool growth and meat quality, reduce immune function, and is associated with greater parasite burdens in sheep. Chronic stress induces alterations in behaviour patterns, particularly activity and feeding, and circadian rhythms of behaviour. Stereotypic behaviours, however, are infrequent in sheep and may occur only in experimental conditions of social isolation. Behavioural and physiological data suggest that rough handling and sheepdogs may be sources of chronic stress for sheep. Social subordination and weaning also act as chronic stressors, leading to higher parasitism in these animals and a greater response to additional stressors. Lameness and parasitism are associated with physiological and behavioural responses indicating that these are severe forms of chronic stress in sheep. It is unclear whether environmental stressors, such as weather and food availability, induce chronic stress in sheep. Under-nutrition may, however, be a welfare concern through its impact on lamb survival. The existence of many sources of chronic stress in the management of sheep suggests that the welfare of this species requires more attention than it has currently received.
Welfare assessment in extensive animal production systems: challenges and opportunities
- SP Turner, CM Dwyer
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- Journal:
- Animal Welfare / Volume 16 / Issue 2 / May 2007
- Published online by Cambridge University Press:
- 11 January 2023, pp. 189-192
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The welfare of animals in extensive systems has received little attention despite significant welfare challenges in these environments. Additionally, recent reform of Common Agricultural Policy payments in the EU have put increasing financial emphasis on farmers to attain improved levels of animal welfare, although suitable methodologies for assessing animal welfare are lacking. Assessment of welfare in intensive systems frequently involves assessing compliance with buildings and space requirements, as well as behavioural observations of animals in their home pens and monitoring of health records. In extensive systems, however, many of these measures are inappropriate or impossible. Environments are often heterogeneous, animals may be difficult to observe, individuals may not be identifiable and health records may be limited or completely lacking. The expression of fear by extensive animals, which rarely come into close contact with humans, often limits the value and practicality of behavioural observations as welfare indicators. Currently, welfare audits of extensive farms rely greatly on mortality and morbidity records to determine welfare status. Whilst these measures are important, the strong health monitoring bias does not adequately allow an interpretation of the emotional experiences of extensive animals. We suggest that developing methodologies based on assessing key features of the environment, such as handling facilities, assessment of the skills, knowledge and planning of the stockperson, and assessing the animal at key points in the production cycle when they are gathered may allow a workable methodology for assessing animal welfare to be developed for extensive systems.
How has the risk of predation shaped the behavioural responses of sheep to fear and distress?
- CM Dwyer
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- Journal:
- Animal Welfare / Volume 13 / Issue 3 / August 2004
- Published online by Cambridge University Press:
- 11 January 2023, pp. 269-281
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To use behaviours as indicators of stress it is important to understand their underlying causation. For a prey animal in the wild, such as a sheep, behavioural responses have evolved to evade detection and capture by predators. The behavioural responses of the wild ancestors of domestic sheep to the threat of predation are characterised predominantly by vigilance, flocking, flight to cover and behavioural inhibition once refuge has been reached. Some limited defensive behaviours are seen, mainly in females with young against small predators. Vigilance and flight distance are affected by the animal's assessment of risk and are influenced by the environment, social group size, age, sex and reproductive condition, as well as by previous experience with potential predators. Under conditions of stress, domestic sheep show similar behavioural reactions to wild sheep, although the threshold at which they are elicited may be elevated. This is particularly evident when comparing less selected hill breeds with more highly selected lowland breeds, and suggests that a continuum of responsiveness exists between wild and feral sheep, through hill breeds to the lowland sheep breeds. However, this may be confounded by the previous experience of the breeds, particularly their familiarity with humans. Behavioural and neurobiological evidence suggests that, although the behavioural response to predators (vigilance, flight) is innate, the stimuli that elicit this behavioural pattern may have a learned component. Since vigilance and flight distances are affected by the animal's perception of threat, they may be useful indices of stress in sheep and, as graded responses, give some indication of the level of threat experienced by the sheep. Thus they may indicate the amount of fear or distress experienced by the sheep and hence have the potential to be used in the assessment of welfare states.
Interactions between profit and welfare on extensive sheep farms
- AW Stott, B Vosough Ahmadi, CM Dwyer, B Kupiec, C Morgan-Davies, CE Milne, S Ringrose, P Goddard, K Phillips, A Waterhouse
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- Journal:
- Animal Welfare / Volume 21 / Issue S1 / May 2012
- Published online by Cambridge University Press:
- 01 January 2023, pp. 57-64
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Extensive sheep farming systems make an important contribution to socio-economic well-being and the ‘ecosystem services’ that flow from large areas of the UK and elsewhere. They are therefore subject to much policy intervention. However, the animal welfare implications of such interventions and their economic drivers are rarely considered. Under Defra project AW1024 (a further study to assess the interaction between economics, husbandry and animal welfare in large, extensively managed sheep flocks) we therefore assessed the interaction between profit and animal welfare on extensive sheep farms. A detailed inventory of resources, resource deployment and technical performance was constructed for 20 commercial extensive sheep farms in Great Britain (equal numbers from the Scottish Highlands, Cumbria, Peak District and mid-Wales). Farms were drawn from focus groups in these regions where participative research with farmers added further information. These data were summarised and presented to a panel of 12 experts for welfare assessment. We used two welfare assessment methods one drawn from animal welfare science (‘needs’ based) the other from management science (Service Quality Modelling). The methods gave complementary results. The inventory data were also used to build a linear programme (LP) model of sheep, labour and feed-resource management month-by-month on each farm throughout the farming year. By setting the LP to adjust farm management to maximise gross margin under each farm's circumstances we had an objective way to explore resource allocations, their constraints and welfare implications under alternative policy response scenarios. Regression of indicators of extensification (labour per ewe, in-bye land per ewe, hill area per ewe and lambs weaned per ewe) on overall welfare score explained 0.66 of variation with labour and lambs weaned per ewe both positive coefficients. Neither gross margin nor flock size were correlated with welfare score. Gross margin was also uncorrelated with these indicators of extensification with the exception of labour/ewe, which was negatively correlated with flock size and hence with gross margin. These results suggest animal welfare is best served by reduced extensification while greater profits are found in flock expansion with reduced labour input per ewe and no increase in other inputs or in productivity. Such potential conflicts should be considered as policy adjusts to meet the requirements for sustainable land use in the hills and uplands.
Impact of maternal stress and nutrition on behavioural and physiological outcomes in young lambs
- JA Rooke, G Arnott, CM Dwyer, KMD Rutherford
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- Journal:
- Animal Welfare / Volume 26 / Issue 4 / November 2017
- Published online by Cambridge University Press:
- 01 January 2023, pp. 403-415
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The pre-natal period is of critical importance in defining how individuals respond to their environment throughout life. Stress experienced by pregnant females has detrimental effects on offspring behaviour, health and productivity. The sheep (Ovis aries) has been used as a model to inform human studies; however, in a farming context, the consequences for the lamb of stress experienced by the ewe have received less attention. The stressors that pregnant ewes are most frequently exposed to include sub-optimal nutrition and acute and chronic stressors related to husbandry and the environment. This review focuses upon the young sheep, from around 100 days old until adulthood and uses material identified from a systematic survey of the literature relating to production-relevant maternal stressors and lamb outcomes. Overall, the results demonstrated that stressors imposed upon the ewe altered progeny behavioural and physiological responses. However, detailed analysis of the literature shows several deficiencies in the field, as a whole, which greatly limit the ability to draw conclusions as to how welfare may be affected by pre-natal challenges in commercial sheep. These deficiencies included a lack of consistency in response due to the variety of both stressors imposed and responses measured. Key gaps in knowledge include the impact of ewe disease during pregnancy on outcomes for their progeny and more generally how different commercially relevant stressors interact. Furthermore, there is a need to develop a systematic series of behavioural and physiological measures that can be integrated to provide a holistic and practically applicable picture of offspring welfare.
Genetic parameters for birth difficulty, lamb vigour and lamb sucking ability in Suffolk sheep
- JM Macfarlane, SM Matheson, CM Dwyer
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- Journal:
- Animal Welfare / Volume 19 / Issue S1 / May 2010
- Published online by Cambridge University Press:
- 01 January 2023, pp. 99-105
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This study investigates the genetic basis of lamb vigour (defined as neonatal lamb activity and sucking ability) and lambing difficulty as potential traits to be included in selection programmes to improve ewe and lamb welfare. Scores for lamb birth difficulty, vigour and sucking ability were collected shortly after birth on 1,520 lambs born in 2006 in 19 different flocks that were members of the UK Suffolk Sire Referencing Scheme. Scores evaluated each trait on a scale of 1 to 4; 1 being no assistance given either during birth or to suck, or excellent vigour, through to 4 where a large degree of assistance was required, or poor vigour. Genetic parameters (heritabilities, genetic correlations) were estimated by fitting an individual animal model using ASREML. Variance components obtained from univariate and bivariate analyses were averaged to provide genetic parameter estimates. Heritabilities for birth difficulty and vigour were moderate but heritability for sucking ability was not significant. The genetic correlation between vigour and sucking ability was positive and high, that between vigour and birth difficulty moderately negative, and that between birth difficulty and sucking ability not significant. Birth difficulty and vigour could be included in Suffolk breeding programmes to help reduce health and welfare problems associated with these traits in Suffolk sheep, and in flocks producing crossbred lambs sired by Suffolk rams. Further work is required to evaluate correlations between these traits and performance traits and to comprehensively validate the scoring system once more data become available.