The objectives of this project were: 1) to determine if live animal lung biopsy could be used to characterize early pathologic changes in the bovine lung associated with bovine respiratory disease (BRD), 2) determine if specific infectious respiratory pathogens can be identified in association with early pathological changes, and 3) determine whether pulmonary pathology characterized by live animal lung biopsy at arrival and at the time of initial BRD diagnosis was associated with health and production outcomes of feedlot steers in a commercial feedlot.<p>
A live animal percutaneous lung biopsy technique was developed to obtain a lung sample from the right middle lung lobe in intercostal space (ICS) 4 using a Bard® Magnum® reusable biopsy instrument and a modified 4-mm (8g) biopsy needle. The lung biopsy procedure was limited to 2 attempts per biopsy time. In the technique development, 34 animals chronically affected with BRD were utilized, 20 animals in the preliminary development followed by 14 additional animals in a commercial feedlot setting. The technique resulted in 1 fatality of 34 steers (2.9%) and lung parenchyma was harvested in 19 of 34 steers (55.9%) chronically affected with BRD. In addition, in the commercial feedlot setting this procedure was determined to take about 20 minutes per animal.<p>
The final study was performed on one hundred feedlot steers considered at high risk of developing BRD from twenty pens within a commercial feedlot. Study animals were enrolled in three different groups: sick on arrival (ARR-SA) consisting of 27 study animals and 13 matched control animals; pen pulls with no fever (PP-NF) consisting of 14 study animals and matched 7 controls; and pen pulls with an undifferentiated fever (PP-UF) consisting of 26 study animals and 13 matched controls. Live animal percutaneous lung biopsies were collected from the right middle lung lobe at 3 different times within the first 30 days of the feeding period, about 2 weeks apart. All samples were histopathologically evaluated and were assessed for the presence of <i>Mycoplasma bovis</i>, <i>Mannheimia haemolytica</i>, Histophilus somni and bovine viral diarrhea virus with immunohistochemistry.<p>
A total of 295 lung biopsies were performed yielding 210 (71.2%) lung samples that were sufficient for histopathological evaluation. A histopathology score was awarded to each biopsy based on certain histopathological lesions being present. Only 20 lung biopsy samples from 19 animals received a histopathology score (ie, pulmonary lesions were present) with the most common score being a 1 (maximum score is 20). There were too few lung biopsy samples with a histopathology score to reveal any association with subsequent health events.<p>
Immunohistochemistry (IHC) was performed on all lung biopsies recovered yielding one lung sample to be positive for both <i>Mannheimia haemolytica</i> and <i>Mycoplasma bovis</i> from the PP-UF group. There were too few positive samples to reveal any association between IHC and histopathology score.<p>
A post mortem evaluation was performed by a study veterinarian on all study animals who died or were humanely euthanized due to poor treatment response. In this study only 4 steers died or were euthanized due to poor treatment response and 3 control steers were humanely euthanized. There were too few animals to reveal any association between histopathology score and post mortem diagnosis.<p>
On entry into the feedlot, weights between ARR-SA and the PP-UF and PP-NF groups were significantly different (p<0.05). This is likely an effect of the different processing groups of cattle. At study allocation, the body weights of ARR-SA and PP-UF, PP-UF and their matched controls, and PP-NF and their matched controls were also significantly different (p<0.05). This is likely due to the PP-UF and PP-NF groups experiencing illness for a longer period of time resulting in greater weight loss than the ARR-SA animals as well as the control animals, who were not clinically sick.<p>
The live lung biopsy procedure utilized in this study did not appear to cause any long lasting adverse effects as the BRD case fatality rates from the study animals were comparable to the overall case fatality rates reported by the feedlot for fall placed calves. In fact, the study animals experienced a decreased fatality rate compared to the feedlots overall fatality rate. This may be due to the study animals inadvertently being monitored more closely as the pen checkers were aware of and participating in the study. On post mortem evaluation there was no evidence of adhesions at the biopsy site. This procedure was performed on 134 feedlot steers resulting in only 2 acute deaths as a direct result of the live animal percutaneous lung biopsy procedure.<p>
The results of this study indicate that live animal, percutaneous lung biopsy can be performed safely on feedlot steers in a commercial feedlot with few clinical side effects. In this study there were only 2 fatalities in 134 steers (1.5%) due to the biopsy procedure or 2 fatalities per 349 sampling times (0.6%) This technique did not prove useful either as a diagnostic tool for the determination of early lung pathology in BRD or as prognostic indicator for health and production outcomes. However, this lung biopsy technique may be a useful diagnostic tool for chronic pneumonia assessment.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-07212009-100638 |
| Date | 06 August 2009 |
| Creators | Burgess, Brandy Ann |
| Contributors | Hendrick, Steve |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-07212009-100638/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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