Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2002
Publication Date: 8/6/2002
Citation: Purdy, C. W., Straus, D. C., Chirase, N., Parker, D. B., Ayers, J. R., Hoover, M. D. Effects of aerosolized endotoxin in feedyard dust on weanling goats. Small Ruminant Research. 2002. v. 46. p. 133-147.
Interpretive Summary: The effect of inhaled feedyard dust/endotoxin (ET) on the health of ruminants is unknown. Feedyard dust contains a high concentration of ET which are derived from the outer-cell-wall of all Gram-negative bacteria. Gram-negative bacteria are normal inhabitants of manure and when manure dries and it is walked on it turns to dust. It was determined that dust containing ET when inhaled for 4 hrs by goats caused the following: 1) mean rectal temperature to increase, 2) mean total white blood cells (WBC) to increase, and 3) mean total neutrophils to increase. The rectal temperature increases occurred between 4 and 12 hrs, and the increase in total WBC and neutrophils occurred 8 to 12 hrs after the dust challenge. It was also determined that it was the ET part of the dust and not the microbes that caused the significant increases in the dust treated goats compared to the control goats. Four-thousand-five-hundred g of feedyard dust was divided into three equal samples; sample one was autoclaved for 15 min (AD dust), sample two was oven-heated at 180**o C for 6 hrs (OH dust), and sample three was left untreated (UT dust). The UT dust contained 26.9 micrograms ET/g of dust and viable bacteria and fungi, AD dust contained 13.3 micrograms ET/g of dust and no viable microbes, and the OH dust contained 0.0173 micrograms ET/g of dust and no microbes. Goats treated 4 hrs with either the AU dust or the UT dust increased in rectal temperature, total WBC, and neutrophils, however, the OH dust did not cause the increases. Conclusion: only the ET part of the dust caused the increases in goat rectal temperatures, total WBCs, and neutrophils, and not the viable microbes.
Technical Abstract: Two endotoxin (ET)/dust experiments are reported. Experiment one, weanling female Spanish goats (n=36) were randomly allotted to 4 treatment groups (n=9/group). Principals were exposed to twenty-two 4-hr dust treatments in a closed tent. Four hr after the 1st dust treatment, the mean rectal temperatures of the two principal groups were significantly (P = 0.0016) higher than the controls. It appears that repeated ET/dust exposures induces a state of tolerance for increased rectal temps. Experiment two, twenty-four mixed sex, weanling goats were randomly allotted to 4 treatment groups: principals received autoclaved dust (n=6), controls received non- autoclaved dust (n=6), principals received dry-heat dust (n=6), and controls non-dry heat dust (n=6). Principals were treated with appropriate dust for one 4-hr treatment in a closed tent. The data from principal dust group (n=9) and control non-dust group (n=9) were added from experiment one eafter one 4-hr dust treatment. The ET concentrations was determined for autoclaved dust [13.3 micrograms ET/g], dry-heated dust (0.173 micrograms ET/g), and non-treated dust 26.9 micrograms ET/g. The tent aerosolized dust concentrations were: autoclaved dust 0.369 g/m**3/min with 4.904 micrograms ET/m**3/min; dry-heated dust 0.347 g/m**3/min with 0.0015 micrograms ET/m**3/min. These ET aerosol concentrations caused the autoclave dust goat group and the non-treated dust goat group to significantly increase their rectal temperatures at 4 and 8 hr and total WBC increased at 12 and 24 hr compared to their respective non-dust control groups. The dry-heat aerosol dust ET concentration in the tent did not induce an increased mean rectal temp response or an increased mean total WBC count. Of the 3 principal dust products only the non-treated dust contained viable microbes.