RELATIONSHIPS BETWEEN TREATMENT FOR RESPIRATORY DISEASE, THE PRESENCE OF PULMONARY LESIONS AT SLAUGHTER, AND RATE OF GAIN IN FEEDLOT CATTLE

Authors: WITTUM, THOMAS - OHIO STATE UNIVERSITY; WOOLLEN, NEAL - US ARMY MED RES INST; PERINO, LOUIS - UNIVERSITY OF NEBRASKA; LITTLEDIKE, ERNEST - OMAHA COLL HLTH CAREERS

Submitted to: Journal of the American Veterinary Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: We used observational data to quantify the effects of treatment for respiratory disease and the presence of pulmonary lesions at slaughter on rate of gain in feedlot cattle. The study population consisted of 469 crossbred steers born during three consecutive calving seasons at the U.S. Meat Animal Research Center. Calves were weaned at approximately 6 mo of age, and entered directly in the Center's feedlot where they remained for a mean 273-d feeding period. During the feeding period, cases of clinical respiratory disease and individual weights were recorded. At slaughter, lungs were collected and classified as to the presence or absence of gross lesions. Mean average daily gain was 1.3 kg, and ranged from 1.16 to 1.46 kg within individual pens. Twenty-eight percent of the calves received treatment for clinical respiratory disease during the feeding period, while 72% had pulmonary lesions present at slaughter. Among calves which had been treated for respiratory disease, 78% subsequently had lesions, while 68% of untreated calves were observed with lesions. Pulmonary lesions present at slaughter were associated (P < .01) with a .076 kg reduction in average daily gain during the feeding period. Treatment for respiratory disease did not describe a significant amount of the variation in feedlot average daily gain following adjustment for the effect of lesions. Thus, asymptomatic respiratory disease was apparently common in this population, with an effect on average daily gain similar to that of clinical disease. These data suggest that the therapeutic treatment of clinical cases is not adequate to prevent significant production losses due to respiratory disease in feedlot cattle.

Technical Abstract: We used observational data to quantify the effects of treatment for respiratory disease and the presence of pulmonary lesions at slaughter on rate of gain in feedlot cattle. The study population consisted of 469 crossbred steers born during three consecutive calving seasons at the U.S. Meat Animal Research Center. Calves were weaned at approximately 6 mo of age, and entered directly in the Center's feedlot where they remained for a mean 273-d feeding period. During the feeding period, cases of clinical respiratory disease and individual weights were recorded. At slaughter, lungs were collected and classified as to the presence or absence of gross lesions. Mean average daily gain was 1.3 kg, and ranged from 1.16 to 1.46 kg within individual pens. Twenty-eight percent of the calves received treatment for clinical respiratory disease during the feeding period, while 72% had pulmonary lesions present at slaughter. Among calves which had been treated for respiratory disease, 78% subsequently had lesions, while 68% of untreated calves were observed with lesions. Pulmonary lesions present at slaughter were associated (P < .01) with a .076 kg reduction in average daily gain during the feeding period. Treatment for respiratory disease did not describe a significant amount of the variation in feedlot average daily gain following adjustment for the effect of lesions. Thus, asymptomatic respiratory disease was apparently common in this population, with an effect on average daily gain similar to that of clinical disease. These data suggest that the therapeutic treatment of clinical cases is not adequate to prevent significant production losses due to respiratory disease in feedlot cattle.