Effects of aerosolized feedyard dust that contains natural endotoxins on adult sheep

Acute interstitial pneumonia and the biology of 3-methylindole in feedlot cattle

Acute interstitial pneumonia (AIP) of cattle has been recognized for many decades. While the pathogenesis and risk factors for this condition in pastured cattle are relatively well characterized, there remains a poor understanding of the disease as it occurs in intensively fed cattle such as in beef feedlots. Specifically, in pastured cattle, AIP results from excessive ruminal production of the pneumotoxicant 3-methylindole (3-MI). In feedlot cattle, the evidence to substantiate the role of 3-MI is comparatively deficient and further investigations into the cause, pathogenesis, and control are sorely needed. This review highlights our current understanding of AIP with a focus on the disease as it occurs in feedlot cattle. Additionally, it illustrates the need for further work in understanding the specific animal factors (e.g. the ruminal microbiome, and the role of concurrent diseases), management factors (e.g. animal stocking and vaccination protocols), and dietary factors (e.g. dietary supplements) that may impact the development of AIP and which are relatively unique to the feedlot setting. All stakeholders in the beef industry stand to benefit from a greater understanding of what remains a pressing yet poorly understood issue in beef production.

Cow allergen (Bos d2) and endotoxin concentrations are higher in the settled dust of homes proximate to industrial-scale dairy operations

Airborne contaminants produced by industrial agricultural facilities contain chemical and biological compounds that can impact the health of residents living in close proximity. Settled dust can be a reservoir for these contaminants and can influence long-term exposures. In this study, we sampled the indoor- and outdoor-settled dust from 40 homes that varied in proximity to industrial-scale dairies (ISD; industrial-scale dairy, a term used in this paper to describe a large dairy farm and adjacent waste sprayfields, concentrated animal feeding operation or animal feeding operation, that uses industrial processes) in the Yakima Valley, Washington. We analyzed settled dust samples for cow allergen (Bos d2, a cow allergen associated with dander, hair, sweat and urine, it is a member of the lipocalin family of allergens associated with mammals), mouse allergen (Mus m1; major mouse allergen, a mouse urinary allergen, in the lipocalin family), dust mite allergens (Der p1 (Dermatophagoides pteronissinus 1) and Der f1 (Dermatophagoides farinae 1)), and endotoxin (a component of the cell walls of gram negative bacteria, lipopolysaccharide, which can be found in air and dust and can produce a strong inflammatory response). A concentration gradient was observed for Bos d2 and endotoxin measured in outdoor-settled dust samples based on proximity to ISD. Indoor-settled dust concentrations of Bos d2 and endotoxin were also highest in proximal homes. While the associated health effects of exposure to cow allergen in settled dust is unknown, endotoxin at concentrations observed in these proximal homes (100 EU/mg) has been associated with increased negative respiratory health effects. These findings document that biological contaminants emitted from ISDs are elevated in indoor- and outdoor-settled dust samples at homes close to these facilities and extend to as much as three miles (4.8 km) away.

Feedlot Acute Interstitial Pneumonia

Acute interstitial pneumonia (AIP) of feedlot cattle is a sporadically occurring respiratory condition that is often fatal. Affected cattle have a sudden onset of labored breathing. There is no confirmed effective treatment of feedlot AIP; however, administration of antibiotics effective against common bacterial respiratory pathogens and nonsteroidal anti-inflammatory drugs, especially aspirin, has been recommended. Protective strategies are not well defined, but efforts to limit dust exposure and heat stress; to ensure consistent formulation, mixing, and delivery of feed; and to identify and treat infectious respiratory disease in a timely manner may decrease rates of feedlot AIP.

Histopathological analogies in chronic pulmonary lesions between cattle and humans: basis for an alternative animal model

Most of the natural cases of pneumonia in feedlot cattle are characterized by a longer clinical course due to chronic lung lesions. Microscopically, these lesions include interstitial fibroplasia, bronchitis, bronchiectasis, bronchiolitis obliterans, and epithelial metaplasia of the airways. Herein, the aim was to review, under a medical perspective, the pathologic mechanisms operating in these chronic pneumonic lesions in calves. Based on the similarities of these changes to those reported in bronchiolitis obliterans/organising pneumonia (BO/OP) and chronic obstructive pulmonary disease (COPD) in human beings, calves are proposed as an alternative animal model.

Detection of macrocyclic trichothecene mycotoxin in a caprine (goat) tracheal instillation model

This study demonstrates the detection and dynamics of macrocyclic trichothecene mycotoxin (MTM) tissue loading using a commercially available assay in a goat model. The detection of MTMs has been difficult and complex due to the uncertainty of what tissues to examine and when to sample. Twelve goats (two groups of each) were instilled with Stachybotrys chartarum conidial suspension via the trachea. The first group was challenged repeatedly with fungal conidia containing 1 mg/kg of MTM per instillation whereas the second group was exposed once, to spores with a calculated concentration of 5 microg/kg of mycotoxin. These toxin estimates were generated by the QuantiTox(TM) Kit assay; a conidium of S. chartarum possessed 8.5 pg of MTM. After repeated exposure of 3 days, MTM was detected in one of six animals. This animal and two others from the same group had mycotoxin detected in their serum 24 hours after challenge at a comparable level (1.69 ng/mL) to the six animals challenged with a single dose (2.02 ng/mL) at the same time post-instillation. Results showed that MTMs are detectable in experimental animals soon after challenge and contribute to the understanding of the role of these mycotoxins in the disease process following mold exposure.

Effects of aerosolized class C fly ash in weanling goats

OBJECTIVE

To determine effects of repeated aerosol exposures to fly ash dust on respiratory tracts of tent-confined goats.

ANIMALS

12 weanling Boer-Spanish crossbred goats.

PROCEDURE

Goats were randomly assigned to 2 groups: fly ash treatment group (principal goats, n = 6) or control group (control goats, 6). Aerosolized fly ash dust was provided during a 4-hour period for each of 6 applications given over 3 months and one 2-hour application prior to necropsy. Fly ash particle diameters ranged from 0.1 to 130 microm and averaged 17.8 microm, with 1.5% of fly ash particles in the 0.1- to 5-microm-diameter range. A mean +/- SD of 748 +/- 152 g/treatment was delivered inside a tent containing principal goats; control goats were placed inside a similar tent for 4-hour treatments without dust. Following treatment, rectal temperatures were taken at 0, 4, 6, 8, 24, and 72 hours; Hcts were recorded at 0, 24, and 72 hours.

RESULTS

Rectal temperatures were significantly increased at 4, 6, and 8 hours and decreased at 72 hours, compared with 0 hours. Mean +/- SEM Hct values were significantly increased for principal goats (3747 +/- 0.39%), compared with control goats (36.17 +/- 0.42%). A significant increase in the mean area of gross atelectatic lung lesions (1,410 mm2) was found in principal goats (n = 6), compared with control goats (440 mm2; 5).

CONCLUSIONS AND CLINICAL RELEVANCE

An increase in atelectatic lung lesions was observed in principal goats, compared with control goats; however, overall, fly ash dust effects were nontoxic.

Virulence of fungal spores determined by tracheal inoculation of goats following inhalation of aerosolized sterile feedyard dust

OBJECTIVE

To compare the virulence of spores of 7 fungi by tracheal inoculation of goats following exposure of goats to an aerosol of sterilized feedyard dust. Animals-54 weanling Boer-Spanish goats.

PROCEDURE

A prospective randomized controlled study was conducted. There were 7 fungal treatment groups, a tent control group, and a pen control group (n = 6 goats/group). Goats in the 7 treatment and tent control groups were exposed to autoclaved aerosolized feedyard dust for 4 hours in a specially constructed tent. Goats in the 7 treatment groups were then inoculated intratracheally with 30 mL of a fungal spore preparation, whereas tent control goats were intratracheally inoculated with 30 mL of physiologic saline (0.9% NaCI) solution. These treatments were repeated each week for 6 weeks.

RESULTS

Severity of pathologic changes differed significantly among the 7 fungal treatment groups as determined on the basis of gross atelectatic and consolidated lung lesions and histologic lesions of the lungs. Descending order for severity of lesions was Mucor ramosissimus, Trichoderma viride, Chaetomium globosum, Stachybotrys chartarum, Aspergillus fumigatus, Penicillium chrysogenum, and Monotospora lanuginosa. Trichoderma viride spores were the most invasive and were isolated from the bronchial lymph nodes and thoracic fluid of all 6 goats administered this organism. Spores were observed-histologically in lung tissues harvested 72 hours after inoculation from all treatment groups.

CONCLUSIONS AND CLINICAL RELEVANCE

4 of 7 fungal spore types induced significantly larger lung lesions, compared with those induced by the other 3 spore types or those evident in control goats.

Effect of simulated ambient particulate matter exposure on performance, rectal temperature, and leukocytosis of young Spanish goats with or without tilmicosin phosphate

Dust is an environmental stressor and can become extensive in agricultural production systems. Thirty-six female, Spanish goats (average BW 21.1 kg, SEM = 1.31; age = 4 mo) were randomly assigned to simulated dust events or no dust, with or without tilmicosin phosphate treatment in a 2 x 2 factorial arrangement of treatments to determine effects on performance, rectal temperature, and leukocyte changes. All goats were fed a standard growing diet (13.6% CP) consisting of 37% roughage and 63% concentrate (DM basis). Feed intake was measured daily, and BW (unshrunk) measured individually every 7 d. The tilmicosin-treated group received tilmicosin phosphate (10 mg/kg BW s.c.) before starting the study. Goats exposed to dust were enclosed as a group inside a canvass tent for 4 h each day and ground feed yard manure dust (mean particle size 100 microm) was aerosolized inside the tent to simulate a dust event. There was one single dust event (Phase I) followed by rectal temperature measurement, and heparinized blood collection for complete cell counts at 0 (pretrial), 4, 12, 20, 44, 68, and 210 h after dust exposure. This was followed by 21 d of chronic dust events (Phase II). The sampling procedures for Phase II were exactly the same as in Phase I, except that samples were obtained daily at 0 (before dust application), 4, 8, and 12 h after each dust event. Dust treatment had no effect (P > 0.05) on feed intake or ADG, but the gain:feed (G:F) ratio was lower (P < 0.05) in the control goats than the dust exposed group. Tilmicosin phosphate-treated goats had a higher (P < 0.05) G:F ratio than untreated goats. Dust exposure increased (P < 0.002), but tilmicosin treatment decreased (P < 0.05) rectal temperature at 4 and 8 h. Dust exposure increased (P < 0.02) blood lymphocyte counts compared with controls. These results suggest that simulated dust events altered rectal temperature and leukocyte counts of goats.

Comparison of the type and number of microorganisms and concentration of endotoxin in the air of feedyards in the Southern High Plains

OBJECTIVES

To determine the bacterial, fungal, and endotoxin concentrations in aerosolized ambient air during the winter and summer in feedyards located in the Southern High Plains, identify aerosolized microbial pathogens, and determine the size of microbial and dust components.

SAMPLE POPULATION

Aerosol samples were obtained from 7 feedyards.

PROCEDURE

Aerosol samples were collected upwind, on-site, and downwind from each feedyard at a point 1 m above the ground by use of biological 2- and 6-stage cascade impactors.

RESULTS

Significantly more microbes were cultured from on-site and downwind samples than upwind samples. There were significantly more microbes during the summer than during the winter. However, mean endotoxin concentration was significantly higher during the winter (8.37 ng/m3) than the summer (2.63 ng/m3). Among 7 feedyards, mean +/- SE number of mesophilic bacteria (1,441 +/- 195 colony-forming units [CFUs]/m3) was significantly higher than mean number of anaerobic bacteria (751 +/- 133 CFUs/m3) or thermophilic bacteria (54 +/- 10 CFUs/m3) in feedyard air. Feedyard aerosol samples contained more mesophilic fungi (78 +/- 7 CFUs/m3) than thermophilic fungi (2 +/- 0.2 CFUs/m3). Eighteen genera of bacteria were identified by use of an automated identification system.

CONCLUSIONS AND CLINICAL RELEVANCE

It appeared that gram-negative enteric pathogens offered little risk to remote calves or humans via ambient aerosols and that gram-positive pathogens of the Bacillus, Corynebacterium, and Staphylococcus spp can be spread by aerosols in and around feedyards. It was common to detect concentrations of endotoxin in the ambient air of 7 feedyards.

Airborne microbial flora in a cattle feedlot

A total of 1,408 cattle held in eight commercial feedlot pens were used to examine the quantity and diversity of microorganisms in cattle feedlot air. The effect of two feeding patterns on the generation of airborne dust and the total numbers of microorganisms was also examined (four feedlot pens/treatment). Microbial samples were collected, and dust particles that were 2.5 microm or less in diameter were measured with a Dustrak monitor during the evening dust peak for 4 days at sites both upwind and downwind of the feedlot pens. An Andersen biological cascade sampler was employed with different medium and incubation combinations for the capture and identification of bacteria and fungi. The results showed that when bacteria were considered, only nonpathogenic gram-positive organisms were recovered. However, gram-negative bacteria may have been present in a viable but nonculturable state. Fungi were recovered in smaller numbers than bacteria, and none of the fungi were pathogenic. The Dustrak results showed that one feeding pattern resulted in cattle behavior that generated levels of downwind dust lower (P = 0.04) than the levels generated by the behavior resulting from the other feeding pattern. However, the Andersen sampler results showed that there were no differences between feeding patterns with regard to the total number or diversity of microorganisms. The disparity may have been due to the different operating principles of the two systems. The overall numbers of microorganisms recovered were lower than those reported in studies of intensively housed farm animals in which similar recovery techniques were used.