When animals are stressed, their bodies release cortisol as a stress response. Cortisol is a hormone that helps the animal escape stressors by giving it extra energy, this could however be detrimental to the animal’s health if the stress continues over a long period.
Homeostasis occurs when the body is able to maintain a stable internal environment in response to external changes. An example of this is when animals seek shade and drink more water on hot days, to maintain stability.
Stressors are external factors that can have negative effects on homeostasis, especially when they are prolonged. Animals can even experience stress during normal routine handling. This can make them more susceptible to disease. Cortisol, a steroid hormone, is then released to provide the animal with energy for their ‘fight-or-flight’ response.
Though this may be a good thing, frequent release of cortisol due to stress can lead to reproductive challenges and disease as a result of compromised immunity. Often farmers will complain that vaccines are not effective, but this could be a result of their high levels of cortisol, which prohibit efficient immune responses.
Mannheimia haemolytica and coccidiosis are usually linked to stress. Vaccinations and continuous exposure to non-fatal doses help to strengthen animals’ immune systems, but stress can lower their immunity to such an extent that they succumb to disease.
Both M. haemolytica and Pasteurella multocida (pasteurellosis) are lung infections, and are one of the greatest causes of economic loss in ruminants. These diseases are often encountered in feedlots and bull testing centres after seasons change warm to a cold. Young growing cattle are especially susceptible to these diseases.
Eimeria parasites cause Coccidiosis in cattle. This most commonly occurs in young animals when they are moved from pasture to feedlots. This can result in a high morbidity, but low fatality rate in affected animals. Poor production also often occurs in animals that recovering. Symptoms of Coccidiosis include diarrhoea, with or without blood and mucous; dehydration; emaciation; and malaise.
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