Stress
- stress is an environmental effect on an animal which over-taxes its control systems and reduces its fitness. Fitness is th variable(s) that are ultimately limted by exposure to stress. Stressors areenvironmental factors which lead to stress.
- Glucocorticoids (steroid hormones) sppres the inflammatory and immune response and are associated with formation of a gastro-intestinal ulcers
- Selye identified 4 stages in sress: alarm reaction, physiological resistane to the disturbance, exhaustion of the adaptive processes, death.
- responses to adverse situations range considerably. Not all adverse situations elicit adrenal cortical responses such as dehydration in sheep or high environmental temperature. Glucocorticoids are also released in response to situations not normally regarded as stressful such as courtship, copulation and hunting.
- If an animal encounters a severe stimulus its response may be domintaed by physiological mechanisms that have evolved tocope with such emergencies such as the withdrawal reflex or oreination reaction and this can be an issue when animals are housed together.
- welfare is the state of an animal as it atempts to cope with an environmental change and will vary in a continuum from poor to good. It is important to distinguish those effects which reduce fitness from those which do not. Animals may go throuhg difficult periods but may succeed in coping without any long-term effects. Animals may go through difficult periods but may succeed in coping without any long-term effects. Attempts to cope include functioning of body repair systems, immunological defnse mechanisms, emergency physioloical responses, variety of behavioural processes but it needs to be measured in a scientific manner.
- If an animal's welfare is por when it is having difficulty in coping or is failing to cope- this implies fitness reduction and stress.
- Animals use a variety of methods whne trying to cope and there are various consequences of failure to cope.
- Pain and suffering are important aspects of poor welfare.
- reduced life expectancy
- reduced ability to grow or breed
- body damage
- disease
- immunosuppression
- physical attempts to cope
- behavioural attempts to cope
- behaviour pathology
- self narcotisation
- extent of behavioural aversion shown
- extent of suppression of normal behaviour
- extent to which normal physiological proceses and anatomical development are prevented.
- variety of normal behaviours shown
- extent to which strongly preferred behaviours can be shown
- physiological indicators of pleasure (reduced cortisol, increased dopamine, better immune function)
- beavioural indicators of pleasure (play, grooming)
- an animal encountering a varied environment but wih no real problems will show only occasional bouts of adrenal cortex actvity = good welfare
- an animal that is frequently frustrated or frightened might have increased glucocorticoid production and synthetic enxyme activity in the adrenal cortex= poorer welfare.
- adrenal cortex function can b tested by repeated unpleasant stimulai which may sensitise the hypothalamic-pituitary-adrenal axis so that a test with a novel disturbing stimulus elicts a greater response.
- the Adrenocorticotrophic Hormon (ACTH) Challenge test, tests increased synthetic enzyme activity of the adrenal cortex.
- Levels of immunosuppression may also correlate with levels of welfare (may or may not be mediated by hyperactivity of the adrenal cortex). Changes may be preceded or accompanied by behavioural indicators of poor welfare. When welfare is good, the immune system works effectively to counteract challenge by pathogens.
- stereotypies are repeated, relativel invariant sequences of mvoements with no obvious function such as bar biting or sham chewing in sows or crib biting in horses and is possibly due to furstration or lack of control over their environment. Sham chewing is typically seen in singly stalled sows in which no straw is provided and is constant chewin with the mouth gaping and forthing, he sows are often underweight and have delayed return to oestrus after weaning. Tongue rolling is well described in cattle and includes components of the mvoements involved in prehension of forage plants during grazing and can endure for a few minutes to a few hours.
- subjective feelings are important aspects of welfare. Pleasant and unpleasant feelings are pat of th experience of an individual as it attempts to cope with its environment. Suffering occurs when unpleasant subjective feelings are accute or continue for a long time because the animal is unable tocarry out the actions that normally reduce risks to life and reproduction in these circumstances.
- Recognising and assessing animal feelings can be a considerable problem, suffering is an important aspect of poor welfare so we need ways of identifying suffering and devising ways to prevent it.
- how can welfare be measured scientifically?
- What is a challenge regarding recognising suffering?
- what is stress and how is it presented?
- describe a measure of good and poor welfare.