Submitted to: American Journal of Veterinary Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/9/2001
Publication Date: 1/1/2002
Citation: Purdy, C.W., Straus, D.C., Chirse, N., Parker, D.P., Ayers, J.R., Hoover, M.D. 2002. Effects of aerosolized feedyard dust that contains natural endotoxins on adult sheep. American Journal of Veterinary Research. 63(1):28-35. Interpretive Summary: Dust in feedyards is a common finding in a semi-arid climate as any downwind neighbor knows. Much of the dust comes from manure which dries and is ground into dust when calves play and walk on it to and from the feed bunks and waters. Manure contains endotoxins which originate from the Gram-negative bacterium outer membranes. Gram-negative bacteria are indigenous to manure flora in animals and man. Endotoxins are very heat stable and resist environmental destruction. In addition, they are very biologically active as aerosolized dust particles, which induce a fever and an increased white blood cell count in humans. It is not known what effects they have on ruminant health, rate of gain, and feed efficiency. It was determined that endotoxin induce an acute transitory fever within 8 hours after it was administered and it also induced an increase in total white blood cells in adult sheep after 12 to 24 hours. Therefore, endotoxin/dust affects the health of ruminants and may be an additional significant stressor in market stressed ruminants which are prone to pneumonia after marketing and transport.
Technical Abstract: Eighteen three year old Saint Croix sheep were used in a prospective, randomized controlled study with two treatment groups: endotoxin/dust principals (n=9) and controls (n=9). Aerosolized feedyard dust was given continuously over a four hour period for each dust treatment to the principals in a semi-air-tight tent. The principal group was given endotoxin/dust one day in week one, three days in week two, and seven days in week three. The control group was placed in a non-dust tent on the same days and at the same time as the principal group. All sheep were euthanatized and necropsied eight hours after the principal group received their last dust treatment. The following variables were measured prior to and after each dust treatment: rectal body temperature, total white blood cell count (WBC), fibrinogen, and haptoglobin. The variables were also measured (4 hr, 8 hr, 12 hr, and 24 hr) after the dust treatments. The average amount of dust administered during each dust treatment was 451 g i 4-hr. The principal group mean rectal body temperature was significantly higher (40.4 C) at 8 hr post dust treatment than the mean for the control group. The mean WBC count of the principal group was significantly higher at 12 hr, and 24 hr than the mean of the control group. There were no significant differences in mean fibrinogen and haptoglobin concentrations between the groups. Similar responses were observed with repeated endotoxin/dust treatments; however, with each subsequent dust treatment there was a diminished response. No gross lung lesions were observed. In conclusion, 51 mg dust/m**3 and 7423 ng endotoxin in the feedyard dust induced a temporary febrile response and leukocytosis in the principal group compared to the control group.