The North American beef cattle industry has endured many changes throughout the years but is encountering some of the most dramatic challenges in history during the first decade of the 21st century. The US beef cattle inventory increased from 1990 to a high of 103.5 million in 1996 and since has declined to a low of 94.5 million on 1 January 2009. Even though economic signals have encouraged the cow herd to increase over the last 5 years, a significant decrease occurred during 2008. It is difficult to determine the precise cost of bovine respiratory disease (BRD) to the industry but it is reported to be greater than US$500 million per year. Data from our practice indicate that losses from BRD over the last 18 years have been characterized by 5-year cycles of decreases and increases. Perhaps it is time for the industry to look for ways to reduce death loss by methods that focus on the animal's response to the pathogens instead of continuing to focus on the pathogens.

Analysis of these results suggests that AIP in feedlot cattle is not a consequence of infection with BRSV. The increased, risk of isolation of an aerobic bacterial agent from cattle with AIP, compared with control cattle, may indicate a causal role or an opportunistic infection that follows development of AIP.

Increased pulmonary production of 3MEIN may be an important etiologic factor in feedlot-associated AIP.

SUMMARYA series of animal feeding trials was designed to determine differences between grasses in dry-matter intake and animal live-weight gain, with a view to indicating better selection criteria for improving the feeding value of herbage.Wide differences were demonstrated in feed intake and live-weight gain between single-variety grass feeds at similar levels of digestibility.S.37 cocksfoot gave consistently good and S.51 timothy, consistently poor responses.Supplementation of grass feeds with red clover frequently resulted in marked improvement in feed intake and animal performance.

Diagnosis of deaths due to digestive disorders can be a difficult task. It is helpful if the carcass can be viewed for condition, position, and location before being moved from the pen in which it was found. A complete necropsy is absolutely necessary even though postmortem decomposition may be advanced. All thoracic and abdominal organs must be examined for gross lesions. If one believes that the central nervous system was involved, the brain should be removed and examined. Checking the ruminal pH is important. If indicated, samples should be obtained and submitted to a diagnostic laboratory. Salient lesions include congestion of the anterior portion of the carcass, especially the cervical muscles and tissues adjacent to the esophagus and trachea, paleness of the posterior portion of the carcass, edema between the muscle groups of the hindquarters, scrotal, or mammary area, and a lack of other gross lesions. Many cases have congestion and(or) edema in the submucosa of the dorsal portion of the trachea extending from the thoracic inlet cranially. One must list the cause of death as unknown or undetermined when it is not apparent.