The effect of transportation stress on the content of bronchoalveolar lavage (BAL) fluid of 20 male Holstein–Friesian calves, 4–10 months old (mean weight 160 kg) was studied. The calves were healthy and had no previous history of respiratory tract diseases. During a period of 42 days experiment, the calves were kept indoors and were fed alfalfa hay and corn silage ad libitum. After a period of adaptation, on day 21, BAL fluid, blood samples, and nasal swabs were taken from all calves; then, the calves were divided into three groups: experimental (ten calves), which were transported and were deprived of food and water during transportation; control 1 (five calves), which were not transported and had free access to food and water during the 12 h of transportation of the experimental group; and control 2 (five calves), which were not transported but were deprived of food and water for the same time as the experimental group. On day 26, BAL fluid samples and nasal swabs were taken from control group 1. Blood samples were collected simultaneously from all groups at 0, 1, 3, 6, and 12 h of transportation. On days 27, 31, and 42, all previous samplings (BAL fluid, blood, and nasal swabs) were conducted on the experimental group and control group 2. Cytological, biochemical, and bacteriologic examination of BAL fluid and hematological and biochemical examination of blood samples revealed that the number of red blood cells, white blood cells, neutrophils, and the levels of cortisol, packed cell volume, total protein, and fibrinogen significantly increased, but lymphocytes significantly decreased in the experimental group compared with control groups 1 and 2 on the day of transportation (p<0.05). In addition, regarding BAL fluid content, total cell count, macrophages, neutrophils, and total protein increased in the experimental group (p<0.05). Pasteurella multocida was isolated from BAL fluid of three calves in the experimental group after transportation. Alteration in BAL fluid components in this study may be due to a depressed efficiency of mucociliary system and/or decreased amount of alveolar spatial surfactant either or both of which may predispose affected livestock to show the presence of P. multocida in bronchoalveolar fluid.

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