How To Measure Cortisol Levels In Blood In Animals

Cortisol: often non the best indicator of stress and poor welfare

The definitions of the term stress are often confusing and should not be linked to cortisol, which is a valuable welfare indicator, but context is needed to interpret information technology

Features

Donald Broom
Department of Veterinary Medicine University of Cambridge, UK

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https://doi.org/10.36866/pn.107.30

The glucocorticoid cortisol is produced in many mammals, such equally primates, carnivores and ungulates, and in other animals. Corticosterone has the aforementioned function, being produced in rodents and many birds, including poultry, then reference to cortisol below mostly applies to corticosterone besides. The hypothalamic–pituitary–interrenal response of fish that experience adversity involves interrenal tissue whose cell functions are very similar to those of the mammalian adrenal gland. Maximal concentrations of cortisol are produced in a trout when it is removed from water and hence deprived of oxygen.

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Cortisol in positive and negative situations

A key, adaptive part of the glucocorticoids is to brand free energy available in emergency situations, and in some other situations where it is needed, but they have other important roles. The bulk of cells in the homo body have receptors for cortisol and glucocorticoids attain every organ, thus cortisol has a broad variety of effects, including effects on metabolic, cardiovascular and allowed responses. At that place is a daily fluctuation in the secretion of cortisol, and hence in plasma cortisol concentration, beginning in humans with a distinct sharp ascent of cortisol at the fourth dimension of waking, followed past a steady decline over the class of the mean solar day, with the lowest levels in the early forenoon hours. The cortisol facilitates effective learning, via
the functioning of the hippocampus, and maintains other normal functions in the body (Broom & Zanella, 2004). Hippocampal cells actively take up cortisol in vitro. Farthermost adversity can suppress the daily cortisol wheel in humans (Kivlighan et al., 2008) and pb to less constructive hippocampal role and hence worse learning power and memory.

The facilitation of learning is clearly a positive office, every bit is the increase in cortisol during courtship, mating and exertion to obtain food. Whilst cortisol has an adaptive function for the private when information technology is produced in response to perceived danger, pain or difficulty to control interactions with the surroundings, these situations are negative and at that place may be some substantial negative consequences of the cortisol, every bit described below. Cortisol has roles in both positive and negative situations so it is erroneous to consider it to be e'er or mostly harmful to the individual.

The meanings of stress and welfare

For most people, stress implies the effects of a challenge to the private that disrupts homeostasis resulting in agin furnishings. It is not only a stimulus that activates free energy-releasing control mechanisms. Stimuli whose effects are benign would non be chosen stressors by most people. Likewise, situations that actuate the hypothalamic–pituitary–adrenal cortical axis every bit part of a brief emergency response, but whose furnishings are useful to the private, would not be called stressors by most of the public.

The writings of Selye, although stimulating useful research, have been scientifically confusing in relation to the apply of the term stress. A definition of stress that is in line with the general public usage of the word is, stress is an ecology consequence on an individual which overtaxes its command systems and results in adverse consequences, eventually reduced fitness, (Broom & Johnson, 1993; Broom, 2014). Co-ordinate to this definition, there is no good stress and effects that are called skillful stress should exist called stimulation. During the development of individuals, stimuli that result from situations that are somewhat hard for that individual tin be useful experience but these are all-time not referred to as beingness stressful. This definition is like to that of Lazarus (2006) who said that stress refers to a state of affairs in which demands are perceived to exceed one's personal resources. However, whilst this definition depends on perception, it is better for the definition to depend on function and to apply to all animals.

Scientists and legislators now use animal welfare equally a term that is a scientific concept describing a potentially measurable quality of a living animal at a particular time. The welfare of an private is its state as regards its attempts to cope with its surround. Welfare tin can be measured scientifically and varies over a range from very expert to very poor. Welfare volition exist poor if in that location is difficulty in coping or failure to cope. In that location are various coping strategies with behavioural, physiological, immunological and other components that are coordinated from the brain. Feelings, such as pain, fear and the various forms of pleasure, are often function of a coping strategy and feelings are a cardinal part of welfare. Coping with pathology is necessary if welfare is to exist adept and then health is an important part of welfare. There is a clear relationship between stress and welfare in that, whenever there is stress, welfare will be poor. However, welfare could be temporarily poor without whatever long-lasting agin effect, then this would be poor welfare without stress (Broom & Johnson, 1993).

Writings about the concepts of 'one wellness' and 'one welfare' emphasise that the meanings of scientific terms concerning humans and non-humans should be the same. Still, human usage and definitions sometimes utilize merely to humans and there can exist an erroneous assumption that some mechanisms are confined to humans. The distinction between concrete and psychological stressors may involve the assumption that most non-homo stress is solely concrete. Dedovic et al. (2009) suggest that a stressor facing a wild animal, with the anticipation of actual injury, is concrete while social evaluative threat would be considered psychological. It has been suggested that reactive stressors tend to implicate brainstem, specific hypothalamic nuclei and the bed nucleus of the stria terminalis, which all have direct connections to the paraventricular nucleus whilst anticipatory stressors, seem to engage limbic system regions. This is probable to be valid but does not differentiate not-human and human because the encephalon mechanisms are present in a range of species. A concept of the future and other aspects of sentience are evident from many not-homo studies (Broom, 2014). Health, welfare and stress are the aforementioned concepts in humans and other sentient animals because virtually of the mechanisms are the same.

Cortisol as an indicator of stress and welfare

When humans and other animals are subjected to short-term problems, e.yard. painful procedures, frightening situations such as being picked up or transported, or experiences that cannot be controlled, the increase in cortisol that usually occurs can be measured and used every bit an indicator of the extent of poor welfare. In some cases an experimenter can predict that there volition be long-term harm and then the individual can be said to be stressed. Cortisol concentration in blood and saliva and, later, the concentration of cortisol metabolites in urine, faeces and hair increases when a person hits their finger with a hammer, a rabbit is subjected to a temperature of 42˚C, a calf is loaded onto a transport vehicle, a sheep is driven around bends so that rest is difficult, a pig is introduced into a group of strangers, a salmon is pumped through a pipe, or a wild bird is brought into captivity. The increase tin be assessed in relation to the basal cortisol concentration and the known maximum increase in such an animal. Provided that the sampling of, for example, blood is not itself the cause of whatsoever increment and the time taken for the cortisol increment to occur is taken into account, the magnitude of change gives useful information virtually the subject's welfare (Broom & Fraser, 2015).

An example of cortisol measurement giving useful information near animal welfare is shown in Fig. 1. During a period of monitoring sheep during a road journey, the sheep showed a very marked increment in plasma cortisol from the baseline when they were loaded on to the vehicle. This occurred despite the fact that the staff concerned were experienced animate being handlers and did non treat the animals roughly. The sheep had never earlier been on a vehicle and were clearly very disturbed by the loading. The response lasted for 5–6 hours. The cortisol concentration and so dropped to close to the basal level as the sheep became accustomed to their new surroundings. It did not alter during a ane-60 minutes period when the vehicle was stationary. Most of the journey was on motorways, but the terminal 3 hours of the journey were on side roads with bends at intervals. The drivers drove just equally they would with human passengers. All the same, a sheep continuing on a moving vehicle has much more difficulty maintaining its residue than a human sitting in a seat. Cornering and acceleration caused problems for the sheep, so cortisol concentration increased. Information technology is clear from studies over relatively short periods, like this one, that measurement of cortisol concentration can provide information almost the welfare of animals and help in the formulation of communication almost how to avoid welfare problems for the animals.

Long-term problems may be an accumulation of short-term difficulties in life, each of which is associated with cortisol production. Although this production of cortisol is essential for survival, later on injury or various other bug, if it continues to exist present it can break down the poly peptide in musculus, inhibit the ongoing replacement of calcium in bone and produce myopathy, weakness, fatigue and decalcification of os (Melzack, 2001). Frequent, high levels of cortisol production may atomic number 82 to neural degeneration of the hippocampus, amygdala and pre-frontal cortex and suppression of immune system function (McEwen, 2007). People with Post-Traumatic Stress Disorder and other substantial long-term problems take hippocampal and other brain damage, some mediated via cortisol (Bremner, 1999). Loftier plasma cortisol in elderly men is associated with lower cognitive ability (MacLullich et al., 2005). Glucocorticoid effects on the immune organization may include changes in the numbers of leucocytes, suppressing the activeness of B-cells and cytotoxic T-cells and irresolute cytokine action in ways which increase susceptibility to pathogens. These are clearly negative furnishings on the individual so frequent, loftier concentrations of cortisol are indicators of stress and poor welfare.

However, some environmental conditions, such as housing conditions that do not meet the individual's needs, may not atomic number 82 to a change in cortisol concentration. Hence the absence of an increase in cortisol concentration does not indicate that at that place is no problem for the individual. Many chronic issues pb to attempts to cope not involving cortisol and to other negative effects and then a range of welfare indicators is needed to identify that the individual has a problem. This is true of human and non-man subjects. Damage to the hippocampus and other regions of the brain, clearly an indicator of poor welfare, may exist caused by high-fat diet, alcohol, nutrient brake or sleep impecuniousness with no effects on cortisol. Abnormal behaviour, such as stereotypies or high levels of aggression, are sometimes a very useful indicator of poor welfare in situations where in that location is no elevated cortisol. Fluctuations in cortisol may provide no evidence of poor welfare because they are training for courting or active nutrient-finding. Hence the context in which changes in cortisol occur is essential information for interpretation of the physiological data (Broom & Fraser, 2015).

References

Bremner JD (1999). Does stress impairment the brain?. Biological Psychiatry 45, 797–805.

Broom DM (2014). Sentience and Fauna Welfare (pp. 200). Wallingford: CABI.

Broom DM, Fraser AF (2015). Domestic Animal Behaviour and Welfare, fifth edition. (pp. 472) Wallingford: CABI.

Broom DM, Johnson KG (1993, reprinted with corrections 2000). Stress and Animal Welfare (pp. 211). Dordrecht: Springer.

Broom DM, Zanella AJ (2004). Brain measures which tell us about animal welfare. Fauna Welfare thirteen, S41–S45.

Dedovic One thousand, Duchesne A, Andrews J, Engert V, Pruessner JC (2009). The encephalon and the stress axis: the neural correlates of cortisol regulation in response to stress. Neuroimage 47, 864–871.

Kivlighan KT, DiPietro JA, Costigan KA, Laudenslager ML (2008). Diurnal rhythm of cortisol during tardily pregnancy: associations with maternal psychological well-being and fetal growth. Psychoneuroendocrinology 33(9), 1225–1235.

Lazarus RS (2006). Stress and Emotion: A New Synthesis. New York: Springer.

MacLullich AM, Deary IJ, Starr JM., Ferguson KJ, Wardlaw JM, Seckl JR (2005). Plasma cortisol levels, brain volumes and knowledge in healthy elderly men. Psychoneuroendocrinology xxx, 505–515.

McEwen BS (2007). Physiology and neurobiology of stress and accommodation: central role of the brain. Physiological Reviews 87, 873–904.

Melzack R (2001). Pain and the neuromatrix in the brain. Periodical of Dental Education 65, 1378–1382.

Source: https://www.physoc.org/magazine-articles/cortisol-often-not-the-best-indicator-of-stress-and-poor-welfare/

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