Annual disease incidence in Colorado cow-calf herds participating in rounds 2 and 3 of the National Animal Health Monitoring System from 1986 to 1988.

Thirty-nine and 47 randomly selected Colorado cow-calf operations participated in the National Animal Health Monitoring System (NAHMS) during rounds 2 (October 1986 to September 1987) and 3 (October 1987 to September 1988), respectively. Data on the incidence of disease conditions within each herd were collected by federal and state Veterinary Medical Officers and university veterinarians through monthly visits to the ranches. Annual disease incidence for disease classes and the most frequently reported individual disease conditions were determined and expressed on a per 100 cow basis. The mean annual disease incidences for all diseases in these herds were 48.8 and 47.7 new cases per 100 cows for rounds 2 and 3, respectively. The ranges for herd annual disease incidence were wide in both study years. The enteric disease class had the highest mean annual disease incidence in both years of the study, and this was primarily because of diarrhea of unknown cause in calves. Diarrhea of unknown cause accounted for approximately 25% of all new disease cases in both rounds of the study. The mean annual disease incidences were not different for any disease class between the two rounds. The data indicate that, on the average, diarrhea of unknown cause, pneumonia, dystocia, foot rot (interdigital necrobacillosis), pinkeye (infectious keratoconjunctivitis), respiratory tract infection, death of unknown cause, and nonpregnancy had the highest incidences in these Colorado beef herds during the study period. However, because of the wide variation of the predominant disease problems between herds, a herd's disease history as well as the common disease problems in the geographic area of a herd must be considered in designing a herd health program.