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Physiological measures of welfare 2

Physiological measures of welfare 2. Module 4. Learning objectives. To understand the relationship between welfare and physiology To examine how the neuroendocrine system is associated with welfare To understand how neuroendocrine responses can be used to assess welfare

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Physiological measures of welfare 2

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  1. Physiological measures of welfare 2 Module 4

  2. Learning objectives • To understand the relationship between welfare and physiology • To examine how the neuroendocrine system is associated with welfare • To understand how neuroendocrine responses can be used to assess welfare • The pros/cons of different measures for assessing welfare

  3. Summary of content • Neuroendocrine system • HPA, Anterior and Posterior Pituitary • Measures: • Glucocorticoids - ACTH • Reproductive hormones - Temperature • Pathology - Opioids • Limitations of these measures • Conclusions

  4. Definition of animal welfare (physical status) “Animal welfare is the physical and psychological state of an animal as regards its attempt to cope with its environment” Professor Donald M Broom Colleen Macleod Professor of Animal Welfare University of Cambridge UK

  5. Change in welfare = Change in these states=Physiological responses

  6. Types of response Change in welfare  Activation of CNS   Autonomic nervous responses Neuroendocrine responses

  7. Neuroendocrine system (NS) A welfare change affects three sub-divisions of the NS: • Hypothalamic-Pituitary-Adrenal Axis (HPA) • Anterior pituitary • Posterior pituitary

  8. Hypothalamic-Pituitary-Adrenal Axis (HPA) • Major mediator of endocrine responses • HPA =  mobilisation of energy stores for physical response • HPA mediates responses to: • Stress - Sexual activity • Courtship - Food arrival

  9. HPA cascade Hypothalamus CRH Anterior pituitary gland ACTH Adrenal cortex Glucocorticoids Liver

  10. HPA characteristics • Not as immediate as SAM • Measure of acute welfare changes • For example, plasma glucocorticoids elevated between 2-10 minutes after stimulation • Can remain elevated for hours depending on severity of stimulus

  11. Measurement assessment Pros and cons of measurement techniques in terms of: • Invasiveness • Severity of implantation • Restriction • Restraint required • Disturbance • Effect of sampling on parameter

  12. Glucocorticoids • Species dependent: • Useful acute direct measure

  13. Glucocorticoid example 1 • Cortisol  in lambs in response to: • Tail-docking • Castration (Mellor & Murray, 1989)

  14. Glucocorticoid example 2 • Corticosterone in rats after an aggressive encounter: • Victor: initial , then  • Loser: initial , and remains elevated (Henry & Stephens, 1977)

  15. Glucocorticoid measurement • Analysis: • Enzyme-linked immunosorbent assay • High performance liquid chromatography • Competitive protein binding assay • Radioimmunoassay

  16. Chronic welfare assessment • Indirect assessment of HPA: • Sensitisation of HPA: ACTH challenge test • Brain glucocorticoid receptor levels: • Hippocampus and amygdala

  17. ACTH challenge test • ACTH is administered, and resulting glucocorticoid levels measured • Long periods of overcrowding = Higher cortisol response than controls in dairy cows (Friend et al., 1977)

  18. Brain glucocorticoid receptors • Post-mortem test • Brain samples exposed to radio-labelled glucocorticoids •  receptor levels in rats exposed to prolonged handling and disturbance (Wadham, 1997)

  19. Limitations to HPA - 1 • Individual differences • Early experience • Rats (Levine et al., 1967) • Sex • Rats (Livezey et al., 1985) • Disturbance due to measurement • Human presence, handling, restraint and sampling method

  20. Limitations to HPA - 2 • Other factors causing changes • Species • New World Monkeys (Klostermann et al., 1986) • Metabolism • Timing of sample

  21. Anterior pituitary (AP) Other hormones of the anterior pituitary associated with changes in welfare: • ACTH • Reproductive hormones: • Prolactin • Luteinising hormone (LH) • Follicle stimulating hormone (FSH)

  22. ACTH • Acute measure: • more rapid than glucocorticoids • Short lived • Radioimmunoassay analysis • Levels show diurnal variation • ACTH  in rhesus monkeys when confined and exposed to noise (Kalin et al., 1985)

  23. Reproductive hormones • Associated with other measures indicating change in welfare • Sensitivity: • Prolactin > LH > FSH • Radioimmunoassay analysis • Acute measures =  quickly, remain elevated for hours

  24. Reproductive hormone examples • Prolactin  with handling and blood sampling in rats (Gärtner et al., 1980) •  LH in rats with a novel environment and restraint (Briski & Sylvester, 1987) •  FSH in rats when cage moved short distance (Gärtner et al., 1980)

  25. Reproductive hormone limitations • Sample timing, e.g. • Prolactin = diurnal • LH = pulsatile • Sex, e.g. • Females > males • Stage of oestrus, e.g. • Prolactin: Pro-oestrus > dioestrus • FSH: Pre-ovulatory > ovulatory

  26. Posterior pituitary (PP) Oxytocin from the posterior pituitary is associated with changes in welfare: • Species difference: • Restraint in rats = 5-10 fold  • Confinement and noise in rhesus monkeys =  for 30 minutes

  27. Other measures Other effects of the neuroendocrine and autonomic nervous systems can be used to assess welfare: • Temperature • Opioid levels • Organ pathology

  28. Body temperature Changes in other physiological systems (e.g. adrenal activity) = changes in core body temperature = acute welfare measure • Rat body temperature  induced by: • Storms and unfamiliar people (Georgiev, 1978) •  Body temperature found in: • Defeated tree shrews (von Holst, 1986)

  29. Temperature measurement

  30. Organ Pathology • Chronic welfare changes = wide variety of pathologies • Most are measured post-mortem • Pathologies include: • Adrenal hypertrophy • Kidney lesions • Myocardial lesions • Atherosclerosis

  31. Pathology examples • Social instability in female groups of rats = adrenal hypertrophy (Haller et al., 1999) • Subordinate mice show kidney lesions in the presence of dominant animals (Henry & Stephens-Larson, 1985) • Myocardial lesions associated with longer periods of restraint in pigs (Wutzen et al., 1987)

  32. Opioids • Three types: • Endorphins • Enkephalins • Dynorphins • Functions: • Stress-induced analgesia • Control hormone release

  33. Opioid measurement

  34. Opioid examples •  in plasma ß-endorphin in lambs during castration, tail docking and mulesing (Shutt et al.,1987) • Tethered sows = higher opioid receptor density than group housed sows (Zanella et al., 1992)

  35. Conclusion • Neuroendocrine system = acute and chronic measures of welfare • ANS responses can be measured directly and indirectly • NS measures are limited, so care required in their assessment • Other physiological responses can also be used to assess welfare, including temperature, opioid levels and organ pathology

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