Abstract
Farm breeding of cattle is organized so that the animals are kept in a controlled environment (an closed corner, feeding time, milking time, workers), where daily animal encounter with familiar sounds, smells, movements and equipment. Any positive or negative change of environment causes certain physiological reactions of cattle on it. Negative stimuli (relocation, new technological activities, unidentified sounds and people) disrupt the homeostasis of the animals and lead them into a state of stress. During stress in cattle appears central inhibition of milk ejection from the alveoli of the udder, causing its incomplete emptying which could lead to pathological changes. In stressful situation, there is a connection between nervous (SA system), endocrine (HPA-axis) and the immune system. Stimuli from the outside were obtained through sight, hearing, smell and touch, leading to nerve impulses which then activate the endocrine system (increased levels of cortisol, ?-endorphin, adrenaline, and reducing levels of oxytocin in the blood), whose actions over a long time lead to decline in immune response and susceptibility to disease. Many studies suggest an association between central inhibition of milk ejection and stressful situations (first milking of primiparious cattle, environment changes), but the very principle of inhibition is not fully understood. Some studies indicate an association between endogenous opioids (?-endorphin) and catecholamines (adrenalin) in the central inhibition of milk ejection, however, there is still no clear evidence and there is still plenty to do in this area.
Highlights
Despite thousands of years that have passed since the domestication of animals, animal behavior and animal today resemble their wild ancestors (McBride et al, 1969, Jensen, 1986)
In situations where the animal is exposed to a negative stimuli from the environment triggers the sympathetic way of the central nervous system, activation of the adrenal glands, who release from the catecholamine which are important in the "fight or flight" situation when it increases blood pressure and heart rate, symptoms typical of stress situations
Central inhibition of milk ejection is caused by release of oxytocin from the pituitary gland, and occasionally occurs in cattle production as a result of various stresses, in which decreased levels of oxytocin, and increased levels of β-endorphin, cortisol, ACTH, and catecholamines in blood plasma
Summary
Despite thousands of years that have passed since the domestication of animals, animal behavior and animal today resemble their wild ancestors (McBride et al, 1969, Jensen, 1986). In situations where the animal is exposed to a negative stimuli from the environment triggers the sympathetic way of the central nervous system, activation of the adrenal glands, who release from the catecholamine (adrenalin and noradrenalin) which are important in the "fight or flight" situation when it increases blood pressure and heart rate, symptoms typical of stress situations. Central inhibition of milk ejection is caused by release of oxytocin from the pituitary gland, and occasionally occurs in cattle production as a result of various stresses, in which decreased levels of oxytocin, and increased levels of β-endorphin, cortisol, ACTH, and catecholamines in blood plasma. Adrenalin, noradrenalin and oxytocin levels (Means±S.E.) released before, during and after milking in primiparous ewes (Negrão i Marnet, 2003)
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