Nutritional and dietary interrelationships with diseases of feedlot cattle.

Feedlot economics dictate that highly fermentable rations be fed, leaving the ruminant constantly on the edge of lactic acidosis. Consequently, a number of subtle changes in feed, environment, or management can tip the balance, causing ruminal acidosis. Even though the animal may not die from the immediate effects of a metabolic acidosis, there are sequelae such as mycotic rumenitis, hepatic abscesses, cauda vena cava thrombosis, and pulmonary arterial thromboemolism that may cause subsequent losses. Another condition, typically referred to as atypical interstitial pneumonia/acute bovine pulmonary emphysema is a sporadic cause of death in feedlot animals. This condition is sometimes linked to the feed or hypersensitivities such as dust. At present, it seems the condition is not linked with the above and part of the problem may be undiagnosed bovine respiratory syncytial virus BRSV infection.