Bovine respiratory disease

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 :