Bronchopneumonia with interstitial pneumonia (BIP) has been considered a variant of acute interstitial pneumonia (AIP) rather than a distinct disease. This study compared 18 BIP, 24 bronchopneumonia (BP), and 13 AIP cases in feedlot beef cattle. Grossly, BIP cases typically had cranioventral lung lesions of similar morphology and extent as BP cases, but the caudodorsal lung appeared overinflated, bulged on section, and had interlobular edema and emphysema. Gross diagnosis of BIP had 83% sensitivity and 73% specificity relative to histopathology. Histologic lesions of BIP in cranioventral areas were of chronic BP, while caudodorsal lesions included alveolar and bronchiolar damage and inflammation, interstitial hypercellularity, and multifocal hemorrhages. In BIP cases, cranioventral lung lesions were more chronic than caudodorsal lesions. Histologic scores and microbiology data were comparable in cranioventral lung of BIP versus BP cases and caudodorsal lung of BIP versus AIP cases, with differences reflecting a more chronic disease involving less virulent bacteria in BIP versus BP. Mycoplasma bovis infection was similarly frequent among groups, and a viral cause of BIP was not identified. Lesion morphology and similar blood cytokine concentrations among groups argued against sepsis as a cause of lung injury. Surfactant dysfunction was identified in BIP and BP, and was only partially the result of protein exudation. These and other findings establish BIP as a distinct condition in which chronic cranioventral BP precedes acute caudodorsal interstitial lung disease, supporting a role of chronic inflammation in heightened sensitivity to 3-methylindole or another lung toxicant.

Bronchopneumonia with interstitial pneumonia (BIP) of feedlot cattle is characterized by gross and histologic lesions of cranioventral bronchopneumonia (BP) and caudodorsal interstitial pneumonia. This study described the characteristics and frequency of BIP in western Canadian feedlot cattle and identified epidemiologic differences between BIP and either BP or acute interstitial pneumonia (AIP). The study of 9909 deaths on 4 western Canadian feedlots included 1105 BIP, 1729 BP, and 878 AIP cases. A population of 55 cases with gross, histopathology, and microbiology data was used to validate the primary data set. BIP was the second most common reason for death (or euthanasia) from respiratory disease (1105/9909 cases), and the observed frequency was twice what was expected from random concurrence of BP and AIP. Based on logistic regression models, epidemiologic characteristics of BIP were comparable to those of BP, although BIP cases were more chronic with more instances of clinical illness prior to death. BIP was epidemiologically distinct from AIP. Specifically, BIP more frequently affected steers than heifers, deaths occurred earlier in the feeding period at lower body weights and lower daily weight gains, and BIP cases had longer durations from the first clinical illness to death and more separate instances of clinical illness prior to death. Furthermore, death from BIP mainly occurred in winter and fall, while death from AIP was most frequent in summer. These findings define BIP as a unique condition of feedlot cattle and suggest that chronic BP may promote the development of fatal interstitial lung disease in at-risk 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.

A 15-year-old female Simmental cross-breed cow was presented to the Purdue University Veterinary Teaching Hospital for evaluation of a perifemoral soft tissue mass. Impression smears made from an excisional biopsy contained a population of pleomorphic mesenchymal cells with abundant, periodic acid-Schiff-positive (PAS), intracytoplasmic granular material, and rare elongated multinucleated cells consistent with strap-like cells. A second population of small round cells suggestive of lymphocytes or progenitor cells was also noted. A cytologic diagnosis of sarcoma was made, with rhabdomyosarcoma considered most likely based on the large amount of PAS-positive material (presumed to be glycogen) and the rare strap-like cells. Histopathologic sections contained an unencapsulated, densely cellular neoplasm composed of haphazardly arranged highly pleomorphic mesenchymal cells and a few small round cells. The mesenchymal cells were positive for vimentin, non-specific muscle actin, and myoglobin, and negative for phosphotungstic acid-hematoxylin, smooth muscle actin, and desmin. Glycogen granules were confirmed by transmission electron microscopy. A diagnosis of pleomorphic rhabdomyosarcoma was made. While cytologic findings may suggest rhabdomyosarcoma, cytologic features can be highly variable, and a definitive diagnosis usually requires cytochemical and immunohistochemical staining.

Practical application of formal epidemiology can be a very useful tool in private practice for food animal veterinarians working in the field of herd health/production medicine. Careful and deliberate determination of the outcome variables of interest in each production situation or application provides a logical starting point for establishing the information requirements necessary to measure the defined outcome variables. Subsequently, the collected data can be used for a wide variety of purposes, including disease investigation, monitoring, forecasting and commercial field trials. The successful application of formal epidemiology in herd health/production medicine can serve as a solid basis for establishing long-term productive business relationships with animal agriculture enterprises.

Feedlot Health Management Services Ltd. (FHMS) is a private industry company providing animal health management, nutrition, and production consulting services, as well as individual animal data collection and management tools, to commercial feedlots in Canada and the United States. FHMS has conducted feedlot research for commercial feedlot producers and the global feedlot industry for over 25 years, and conducts over 50 studies annually, including disease investigations; new technology assessments; product safety, efficacy and licensing studies; pathogen and antimicrobial resistance surveillance; individual animal and small pen research pilot studies; and large pen commercial field trials.

A field study was conducted to compare the relative effects of two multivalent viral vaccine programs on animal health, feedlot performance, and carcass characteristics of feedlot calves at high risk of developing undifferentiated fever/bovine respiratory disease (UF/BRD). Upon arrival at the feedlot, 3,264 animals were randomly allocated to one of two experimental groups: PYR5 (Pyramid® 5, Fort Dodge Animal Health, Division of Wyeth, Overland Park, Kansas) or EXP5 (Express® 5, Boehringer Ingelheim Vetmedica, Inc., St. Joseph, Missouri). All animals were re-vaccinated with their respective vaccines at 139 days-on-feed. The initial undifferentiated fever (UF) treatment rate was significantly (P<0.05) lower in the PYR5 group than in the EXP5 group (RR=0.70, 95% CI=0.53-0.93). On a live-weight basis, the dry matter-to-gain ratio (DM:G) was significantly (P<0.05) improved in the PYR5 group compared to the EXP5 group. Yield grades were improved in the PYR5 group, with a significantly (P<0.05) lower proportion of YG USDA 3 carcasses in the PYR5 group compared to the EXP5 group. No significant differences were detected in any other animal health, feedlot performance, or carcass characteristic variables between the experimental groups at the P<0.05 level. The economic analysis showed an advantage of $1.36 US per animal in the PYR5 group due to the lower initial UF treatment rate and proportion of YG USDA 3 carcasses.

A field study was conducted at commercial feedlots to compare the relative efficacy of ceftiofur crystalline free acid (CCFA) and florfenicol-flunixin meglumine (FFM) for undifferentiated fever (UF) treatment in calves that were administered tulathromycin metaphylactically on arrival. At the time of initial diagnosis of UF, experimental calves (n=1,056) were randomly allocated to 2 experimental groups, CCFA and FFM. Calves in the CCFA group (n=530) were administered 3.0 mg/lb (6.6 mg/kg) BW of ceftiofur crystalline free acid subcutaneously (SC) at the base of the ear. Calves in the FFM group (n=526) were administered a combination of 18.1 mg/lb (40.0 mg/kg) florfenicol+1.0 mg/lb (2.2 mg/kg) flunixin meglumine SC in the neck region. The first UF relapse treatment rate was lower in the CCFA group compared to the FFM group (P=0.011). The third UF relapse treatment rate was also reduced in the CCFA group (P=0.032), but no difference was detected in the second UF relapse treatment rate between the 2 groups. No differences in overall chronicity, wastage, salvage slaughter, or mortality rates were detected between the 2 groups at the P?0.05 level. There was a net economic advantage of $10.35/treated animal in the CCFA group, driven primarily by the lower initial UF treatment cost when compared to the FFM group.