Bovine respiratory disease
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the leading cause of economic losses in the beef industry
the lungs of cattle are very brone to infection
within hours bovine respiratory disease can cause any irreversible damage to lung tissue
If untreated BRD can result in a quick death of the affected animal
Or in stunted growth & reduce the meat quality
BRD is triggered by infectious & environmental factors
Examples are respiratory viral infection Or stressful extrinsic conditions affecting the animal's immune system
Naturally occuring bacteria in the naso-pharynx normally cause no problem
but the weakning of immune system allows them to multiply excessively
And infection can spread into the lung
Here tissue resident macrophages recognize & phagocytize the bacteria
the cells are distroyed cytokines & other inflammatory mediators are released
they begin the inflammatory reaction
one of the enzymes activated in the surrounding tissue & immune system cells
Is cyclooxygenase (cox)... resulting in the production of prostaglandins
The prostaglandins dilate local blood vessels...slow down the blood stream
And increase the permeability of vessel walls in this way fluid and cells of the immmun sytem
such as neutrophiles and monocytes are drawn in large Quantities to the site of inflammation
At the same time presence of cytokines such as IL-1 in the blood stream
stimulates the production of prostaglandins in the brain
The hypothalamus reacts by up-regulating body temperature
The immune cells drawn to the inflammation site are producing even more cytokines & prostaglandins
Thus intensifying the inflammation
The bacterial toxins are able to inflict severe damage on the tissue cells
The accumulating immune cells such as neutrophils release Oxygen radicals in order to destroy the bacteria
But these radicals also worsen tissue damage
But why is BRD such common & important disease in cow
Why exactly is the bovine lung soo particularly vulnerable to bacterial infection??
The reasons are both anatomical & physilogical
The reasons are both anatomical & physiological
comparing to the horse ...the capasity of the cow's lung is much smaller it is 1/3 that of a samillar sized horse
It's oxygen need at rest are 2 and half times higher
to satisfy the basal oxygen demand the bovine lung is used much more intensively
Other peculiarities of bovine lung such as high degree of segmentation , lack of collateral ventilation, and large amount of C.T
reducing the lung ability to cope with invading pathogens & the resulting inflammation
once the lung is infected inflammation & bacterial toxins cause lesions to develop ..leading to severe & irreversible damage to
the functioning lung tissue ....the result is the appearance of symptoms of BRD such as :
the economic impact of BRD is enormous :