Retrospective Study of Histomoniasis (Blackhead) in California Turkey Flocks, 2000-2014.

The flagellate parasite Histomonas meleagridis causes a severe disease in turkeys. Since nitarsone, the last antiflagellate feed additive, was withdrawn from the market, H. meleagridis has gained increasing clinical and economic importance, and frequently entire turkey flocks are lost to the disease. Even before the antiflagellate market withdrawal, H. meleagridis has been recognized as a noteworthy disease in commercial turkeys. The aim of this study was to compile and analyze data on histomoniasis outbreaks diagnosed by the California Animal Health and Food Safety System in the years 2000 through 2014 while nitarsone was still available. Sixty-two cases were included in the study. In all cases, the parasite was detected by histopathology. Five cases were from breeder flocks, 44 from commercial meat turkey flocks, and 13 from other flocks such as backyard flocks or pet turkeys. There were between one and eight cases each year with no clear trend over time. Most cases occurred in the warmer months between April and October with a clear peak in August. Turkeys in the flocks with the disease were aged between 2 wk and 15 mo, with a median age of 9 wk. In cases for which mortality was reported, daily mortality ranged between 0.04% and 2% with an average of 0.34% and a median of 0.15%. Five-week mortality in infected houses on three infected ranches was between 1.3% and 68%. In 12 cases, the parasite was observed in organs other than ceca and liver. These included spleen, kidney, bursa of Fabricius, proventriculus, lung, pancreas, and crop. In 58 cases, histomoniasis was considered the most significant and primary diagnosis; in four cases histomoniasis was regarded as an incidental finding. In 14 other outbreaks, detailed information was available. In 11 cases, more than one house on the ranch was affected; in five cases the disease spread to all houses. Total mortality in turkeys from affected flocks ranged between 12% and 65%. In eight flocks, the birds were marketed with a weight that was considered too light. In conclusion, the present study shows that even with nitarsone available as antiflagellate feed, additive histomoniasis was a serious disease of turkeys in the United States with an epidemiology similar to that observed in Europe.

A Novel Mycoplasma sp. Associated with Phallus Disease in Goose Breeders: Pathological and Bacteriological Findings.

In April 2014, poor fertility in a major commercial goose breeder operation in California triggered the submission of six live affected Toulouse ganders ( Anser anser ) to the California Animal Health and Food Safety Laboratory, Turlock branch (University of California-Davis). Toulouse were principally affected among all breeds, and their egg fertility dropped from 65.7% to less than 33.9% in the first 40 days of the 2014 breeding season. The flock consisted of 410 adult birds, 90 males and 320 females, between 2 and 5 yr of age. Inspection of the flock revealed that 44.4% of the Toulouse ganders had severe phallic deformities that prevented them from mating. At postmortem examination, severe yellowish fibrocaseous exudate disrupted the architecture of the phallus and occasionally produced fistulating tracts through the wall of the organ. Microscopically, multifocal lymphoid nodules were noted in the mucosa and submucosa of the phallus and were associated with extensive granulomatous reaction, intralesional bacteria, and spermatozoa. Mycoplasma spp. were isolated from the phallus of affected and nonaffected birds, and PCR protocols targeting the 16S-23S ribosomal RNA intergenic spacer regions and the RNA polymerase beta subunit gene were performed to identify the isolates. Three distinct species were identified on sequencing and analysis using the National Center for Biotechnology Information basic local alignment search tool: Mycoplasma cloacale , Mycoplasma anseris , and an unknown novel Mycoplasma sp. Additionally, Pasteurella multocida , in combination with other bacteria, was also isolated from the phallic lesions and identified as serotype 3 with a DNA profile of 1511 (National Veterinary Service Laboratory). This is the first report of these Mycoplasma spp. and other bacteria associated with reproductive disease in ganders in the United States.

Necrotic Enteritis in Chickens Associated with Clostridium sordellii.

Three outbreaks of necrotic enteritis-like disease associated with Clostridium sordelii were diagnosed in commercial broiler chicken flocks with 18,000 to 31,000 birds between 18 and 26 days old. Clinical signs in the affected flocks included high mortality up to 2% a day, depression, and diarrhea. The main gross changes included segmental dilation of the small intestine with watery contents, gas, mucoid exudate, and roughened and uneven mucosa, occasionally covered with a pseudomembrane. Microscopic lesions in the small intestine were characterized by extensive areas of coagulative necrosis of the villi, fibrinous exudate in the lumen, and high numbers of large, Gram-positive rods, occasionally containing subterminal spores, seen in the necrotic tissue and lumen. These rods were identified as C. sordellii by immunohistochemistry. Clostridium sordellii was isolated in an almost pure culture from the intestine of affected birds. A retrospective study of commercial broiler chicken and turkey submissions to the California Animal Health and Food Safety Laboratory System revealed that C. sordellii had been isolated from intestinal lesions in outbreaks of necrotic enteritis-like disease in 8 of 39 cases, 5 times together with Clostridium perfringens and 3 times alone. The latter three cases are reported here.

Retrospective Study on the Isolation of Ornithobacterium rhinotracheale from Chickens and Turkeys in Central California: 294 cases (2000-12).

Ornithobacterium rhinotracheale is a rod-shaped, gram-negative, and mostly oxidase-positive bacterium that causes respiratory infections in chickens and turkeys worldwide and can also spread to nonrespiratory organs. The present report analyzes 294 cases in which O. rhinotracheale was isolated from turkeys or chickens in central California in the years 2000 through 2012. Two hundred sixteen cases were from turkey flocks and 78 from chicken flocks. The median age of turkey flocks was 8.7 wk; the median age of chicken flocks was 6.4 wk. From turkeys, O. rhinotracheale was more often isolated from August to January than during the rest of the year. Chickens cases were more evenly distributed throughout the year. The organs with the highest isolation rate were the infraorbital sinus and trachea, followed by lungs and air sacs. Isolation from other organs was rare. Pure cultures were obtained from relatively more turkey organs than chicken organs. The organ from which there was the highest chance to obtain a pure culture was the air sac. In 108 turkey flocks (50.0%) and 64 chicken flocks (82.1%) at least one other respiratory pathogen was detected. The most common gross lesions were increased mucus in trachea, caseous or fibrinous exudate in the air sacs, consolidated lungs indicating pneumonia, congested and edematous lungs, and a flattened trachea. For most types of lesions, the percentage of affected turkeys was higher than the percentage of affected chickens. The percentage of birds with lesions was higher if other respiratory pathogens were present. Overall, the host species (turkey or chicken) was a more important factor for the prevalence of most lesions than the detection of other respiratory pathogens. The most common histopathologic lesions in the sinus and trachea were heterophilic or mononuclear inflammatory cell infiltration. In the lungs and air sacs, the inflammation was characterized by heterophilic infiltration and/or fibrin accumulation. These results are helpful in selecting the most appropriate samples for isolation of O. rhinotracheale. In addition, they show the incidence of the bacterium in turkeys and chickens and which lesions can be expected after infection with O. rhinotracheale, and they indicate that in some cases O. rhinotracheale can be the primary, or at least the major, pathogen.

Retrospective study of turkey viral hepatitis in California turkey flocks, 2000-2012.

Turkey viral hepatitis (TVH) is a disease characterized by an inflammation of the liver, and occasionally of the pancreas, of turkeys. Little is known about the occurrence of TVH in turkey flocks; thus, the aim of the present article is to summarize retrospectively 76 cases of TVH diagnosed at the California Animal Health and Food Safety System (CAHFS), University of California, Davis, in the years 2000 through 2012. Flocks diagnosed with TVH were between 7 and 61 days old, with an average age of 29.4 days and a median age of 28 days. In the majority of cases, increased mortality was reported. In 55 cases, gross lesions were present in the liver; the most common lesions were a few to numerous pale white foci in 35 cases. In livers of 74 cases, histologic lesions were observed. Multifocal necrosis with inflammation was observed in livers of 42 cases, inflammation but no necrosis in 22 cases, and necrosis without inflammation in 8 cases. In 17 cases, pale white foci were found in the pancreas; in 4 cases, larger areas of the organ were pale. In 33 cases, histologic changes were observed in the pancreas. Necrosis with inflammation was observed in the pancreas of 17 cases, necrosis without inflammation in 7 cases, and inflammation without necrosis in 9 cases. No Salmonella was isolated from any of the livers cultured. Transmission electron microscopy of liver and pancreas demonstrated viral particles between 23 and 25 nm in two cases. Concurrent diseases were mostly poult enteritis (65 cases), but also respiratory diseases and colibacillosis. TVH occurred more often in turkeys during winter months. In conclusion, TVH was observedon a regular basis in California turkey flocks during the last 12 yr.

Spatial and temporal epidemiology of infectious laryngotracheitis in central California: 2000-2012.

In October of 2005 an outbreak of a vaccine-like strain of infectious laryngotracheitis (ILT), indistinguishable from the chicken embryo origin (CEO)-like vaccine strains, was detected by routine passive surveillance in the Central Valley of California, U. S. A. In response, a highly coordinated industry effort by two companies led to a significant decrease in the incidence of ILT over the same geographic region between 2008-2012. In order to understand the geographic and temporal spread of ILT in California before and after the outbreak, Global Information Systems (GIS) mapping coupled with spatial, temporal, and spatial- temporal statistics were used to identify retrospective and prospective low-rate clustering (i.e., less ILT than statistically expected) and high-rate clustering (i.e., more ILT than statistically expected) of ILT spatially and temporally. Results showed two high-rate retrospective spatial-temporal clusters and one low-rate prospective spatial-temporal cluster which were all statistically significant (P < 0.05). Overall, spatial-temporal clustering accounted for 36.9% of the positive ILT cases, while temporal clustering and spatial clustering done separately each accounted for 0% of the ILT cases, respectively. This demonstrates the utility of combining spatial and temporal clustering for ILT surveillance. Due to the risk of reversion to virulence and spread to immunologically naive broilers, future application of the CEO-based vaccine in the identified high rate spatial-temporal clusters should be avoided and other vaccine alternatives considered in order to avoid repeat outbreaks in those areas. This should especially be followed during the winter months of December, January, and February, which were found to have the highest prevalence of ILT (P < 0.05). Analysis of GIS data within the high-rate clusters showed that wind direction and farm density were minor factors in the spread of ILT. Shared roads may have played a role in the spread of ILT in one of the two high rate spatial-temporal clusters.

Systemic histomoniasis associated with high mortality and unusual lesions in the bursa of Fabricius, kidneys, and lungs in commercial turkeys.

An outbreak of systemic histomoniasis in 9-to-11-wk-old meat-type male turkeys associated with high mortality is reported. Clinical signs in turkeys included anorexia, depression, diarrhea, loss of weight, and increased mortality between 7 and 13 wk of age. Seven-week cumulative mortality in the turkeys of affected houses ranged from 24% in one to 68% in the other compared with 1.3% of turkeys in the house not affected by histomoniasis. Necropsy of the turkeys revealed enlargement of the livers, most of which had numerous pale white nodules ranging in size from 0.3 to 1.5 cm in diameter. Cecal walls were severely thickened, the lumens were distended with caseous cores, and the mucosa was ulcerated. The bursa of Fabricius in four birds was enlarged and contained pale yellow exudate in their lumens. The kidneys, pancreas, and spleens in a few birds had pale or yellow foci. Microscopically, there were multifocal necrosis and granulomatous inflammation in the liver, ceca, peritoneum, bursa of Fabricius, kidneys, lungs, pancreas, proventriculus, and in spleens associated with histomonads. Electron microscopy also confirmed the presence of histomonads in the liver and ceca. This is the first report of naturally occurring systemic histomoniasis in turkeys affecting the bursa of Fabricius, kidneys, lungs, pancreas, and proventriculus.

Intervention strategies for laryngotracheitis: impact of extended downtime and enhanced biosecurity auditing.

An outbreak of vaccinal infectious laryngotracheitis (LT) began in 2005 involving 57 ranches of two broiler companies in California. Standard biosecurity, and cleaning and disinfection programs along with vaccination, did not stop the outbreak. Due to the close proximity and number of birds in the same geographic area, the decision was made by both companies to attempt a joint regional and zonal depopulation strategy. The strategy involved extended downtime between flock placements on ranches located within close proximity to one another. This extended downtime on each ranch ranged from 30 to 91 days. An extensive biosecurity audit, with more than 70 items, was implemented. Briefly, this included heating all houses to 37 C for 100 hr, removing the litter, cleaning and disinfecting everything on the ranches, then again heating the houses to 37 C for 100 hr. Used litter was spread on crops away from poultry, or was sent to a litter processor for pasteurization. Extensive surveillance for LT at 28, 35, and 42 days of age was performed on the initial flocks, which had been placed immediately after the extended downtime. Since completion of this plan in early 2008, LT was diagnosed on only two of the previously 57 affected ranches. Those two ranches, and those within close proximity, went through the extended downtime program and biosecurity audit a second time. Currently, both companies are free of LT. This program lends credence to the importance of cooperation between companies to consider all the ranches within close proximity as the population at risk. In the control of LT in broilers, the program also highlights the necessity for extended downtime and enhanced biosecurity auditing of all flocks.

Comparison of diagnostics techniques in an outbreak of infectious laryngotracheitis from meat chickens.

Various diagnostics techniques were compared for their ability to detect infectious laryngotracheitis (ILT) during an outbreak in chickens aged between 4 and 21 wk. Gross lesions ranged from excess mucus to accumulation of fibrinonecrotic exudate in the larynx and trachea. Syncytial cells with intranuclear inclusion bodies were found in sinus, conjunctiva, larynx, trachea, lung, and air sac. Virus isolation in chicken embryos was attempted in every case. Negative-stain electron microscopy detected herpesvirus in only 6% of the cases. Yet, isolation of ILT virus in the chorioallantoic membrane was presumed by histology in >20% of the samples and confirmed by fluorescent antibody (FA) in 35% of the embryos inoculated with conjunctivas or tracheas from affected birds. Overall, results from histology and FA tests were highly correlated. FA test has the advantage over histology of being diagnostically specific for ILT virus. Polymerase chain reaction was the most sensitive test and detected the viral DNA even in cases where histology and FA were negative. ILT virus DNA was quantified by real-time polymerase chain reaction (Re-Ti ILTV). Histologic and FA results from larynx and trachea were negative if the concentration of the viral DNA was < or =4 of log10. A viral DNA concentration higher than log10 4, as determined by Re-Ti ILTV, was required for clinical ILT to be manifested.

Vitamin A deficiency in turkey poults.

Vitamin A deficiency was diagnosed in a commercial flock of 13,000 4-6-week-old turkey poults in the summer of 2004. The birds were initially submitted for examination because of a 3% increase in the reported daily mortality of the flock. Clinically, affected birds had stunted growth and ruffled feathers, showed signs of incoordination, and were depressed. At necropsy, pale white pseudomembranous to mucoid material was observed on the mucosal surface of the tongue, oral cavity, portions of the esophagus, and the crop of some birds. Histologically, there was squamous metaplasia of the mucosal epithelium of the oral mucosa, esophagus, sinuses, nasal glands, bronchi, proventriculus, and the bursa of Fabricius. Vitamin A was not detected in the feed sample at a detection limit of 0.5 mg/kg. Serum vitamin A concentrations in 7 birds were very low and ranged from 0.05 to 0.1 mg/L. Vitamin A concentrations in livers were extremely low (0.1 mg/kg wet weight, 1/7 poults) or undetectable (< 0.1 mg/kg wet weight, 6/7 poults). A diagnosis of vitamin A deficiency was made based on gross and microscopic lesions and vitamin A concentrations in serum, liver, and feed. To the authors' knowledge, this is the first documented case of vitamin A deficiency in poults submitted from a commercial meat turkey producer comparatively depicting the gross and microscopic lesions with those found in other species of birds and mammals.

Systemic Mycoplasma synoviae infection in broiler chickens.

Systemic Mycoplasma synoviae infection in 47-day-old broiler chickens with septicaemic lesions and increased carcass condemnation rate is reported. The clinical history included respiratory signs and an enlarged keel bursa. Condemnations at the processing plant were due to airsacculitis and keel bursitis. Involvement of several organs, including the keel bursa, liver, spleen, brain, choroid of the eye, nerves and skeletal muscle associated with vasculitis, and the isolation of M. synoviae from the liver and keel bursa are only occasionally seen in field cases. Random amplified polymorphic DNA analysis of the M. synoviae isolated from the broiler chickens in this study had a different pattern when compared with the reference M. synoviae strains, WVU-1853, MS-H and F10-2AS, and another M. synoviae isolated from broiler breeders from the same company, but had a similar DNA pattern to an M. synoviae isolated from broiler chickens and turkeys owned by the same company. This finding suggests a horizontally acquired infection rather than vertical transmission.

Histomoniasis in the bursa of fabricius of chickens.

Histomoniasis was diagnosed in a flock of 6-wk-old commercial chickens. Clinical signs included depression, stilted gait, inappetence, and a slight increase in mortality. At necropsy, there were pale-yellow to dark-gray circular and depressed necrotic lesions in the liver. The ceca were enlarged and impacted with caseous cores. Cecal worms were not observed either at necropsy or on histopathology. Histomonads were demonstrated microscopically within the bursa of Fabricius in addition to the liver, ceca, and spleen. This is the first report of the presence of histomonads in the bursa of Fabricius in commercial chickens.

Effect of feeding green onions (Allium ascalonicum) to White Chinese geese (Threskiornis spinicollis).

Sudden increase in mortality was observed in 2 different flocks of mature breeder geese fed green onions. At necropsy, birds had pale epicardium with random petechiation, sanguinous fluid accumulation in the pericardial sac, and mild swelling of the liver and spleen. Histologically, there was accumulation of hemosiderin in hepatocytes, Kupffer cells of the liver, macrophages, and renal tubules. There was also moderate to severe hepatic necrosis, vacuolation of hepatocytes, splenitis, and renal tubular nephrosis. To assess the effects of green onion ingestion, 2 feeding trials were carried out in 3 mature White Chinese geese. In the first trial, onions were thoroughly mixed with pellet maintenance ration. In the second trial, onions were offered in a separate trough from the pelleted diet. During the 21 days of experiments, the red blood cell count and hematocrit decreased, whereas the polychromasia and reticulocyte estimate increased. The blood changes were more marked in birds from the second feeding trial. Gross and histologic changes were similar in both trials. Mild swelling and severe darkening of the liver were the only significant findings at necropsy. Histologically, the liver looked similar to that seen from the field outbreak. The liver contained moderate amounts of hemosiderin in the hepatocytes and Kupffer cells, and had centrolobular necrosis and vacuolation of hepatocytes. This experimental study demonstrated that anemia and liver pathology could be caused by ingestion of onions. Furthermore, Heinz bodies are not a consistent finding in the blood of geese fed onions.

Phenotypic and genotypic characterization of Salmonella arizonae from an integrated turkey operation.

Fifty cases submitted between 2000 and 2002 were selected for retrospective analysis to evaluate possible relationships between Salmonella arizonae isolated from breeder flocks, hatching eggs, and meat bird flocks belonging to a single turkey integrator. In all the meat bird cases selected for this study, arizonosis was the primary diagnosis. In birds under 1 month of age, clinical signs and pathologic changes were observed in older birds. The Salmonella arizonae isolates were analyzed by antibiotic resistance pattern and serotype and genotyped by pulsed-field gel electrophoresis (PFGE). Serotyping and PFGE yielded similar results, but the antibiotic resistance patterns did not correspond to either serotyping or PFGE typing. The presence of common pulsed-field patterns in breeder flocks, eggs, and meat bird flocks suggested that S. arizonae was being transmitted vertically from the breeder flock.

Focal transmural necrotic tracheitis in commercial meat turkeys.

This report describes an unusual presentation of severe focal necrotic tracheitis in a flock of 8-wk-old commercial turkeys. The flock was kept on a range that is located near a cotton field. The cotton field had been chemically defoliated 2 wk before the birds were submitted for necropsy. At necropsy, most of the birds had a 1-cm, yellow-white constricture in the upper third of the trachea at which the lumen was partially occluded by necrotic tissue. Microscopically, there was severe, transmural necrosis with an accumulation of inflammatory exudate in the tracheal lumen and numerous bacteria within the necrotic debris, mucosa, and lamina propria. Mixed bacteria were isolated from the trachea. No viruses were detected. Neither abnormal heavy metal concentrations in the liver nor paraquat in the respiratory tract were detected. The exact cause of this severe, necrotic tracheitis was not determined. Based on the clinical history and laboratory findings, it was concluded that a combination of a toxic irritant, possibly an aerosolized cotton defoliant, and bacterial infections were likely the cause of this lesion.

Microstructure and mineral content of femora in male turkeys with and without fractures.

Microscopic and radiographic observations, as well as ash, calcium, phosphorus, copper, manganese, and zinc concentrations, were evaluated from femora of 32- to 35-wk-old male turkeys from two different farms (A and B). Turkeys from Farm A were divided into birds with femoral fracture (AF) and without femoral fracture (ANF). Turkeys from Farm B did not have femoral fractures (BNF). In the mid-diaphyseal cortex of turkeys without femoral fractures, collagen fibers were evenly distributed parallel to the transverse plane of bone surface. In contrast, collagen fibers were disorganized and the cortex was osteoporotic in turkeys with femoral fractures. Each turkey with femoral fractures also had callus on the mediocaudal region of the femoral middiaphysis. The periosteal callus was interrupted at the insertion of the puboischiofemoralis muscle. Muscle attachment to the bone might have interfered with the formation of periosteal callus. The concentration of calcium was lower in the cortex of turkeys in group AF compared to turkeys in groups ANF and BNF. The focal nature of the callus, along with the low levels of calcium, is indicative of a local repair response with alteration in cortical structure and altered concentrations of minerals in the cortex. These changes in the bone and the routine handling of the birds might have predisposed the turkeys to complete fractures of the femur.

Isolation of an unidentified, nonfermentative, gram-negative bacterium from turkeys and chickens: 38 cases (1995-2001).

Thirty-eight cases were identified in which a nonfermentative, gram-negative, rod-shaped bacterium was isolated from the respiratory system of turkeys and chickens. Cases were submitted from various parts of the country. Preliminary assessment of phenotypic characteristics indicated this bacterium was different from common pathogenic or opportunistic bacteria isolated from the avian respiratory tract. Most cases reported a history of respiratory distress and/or increased flock mortality. Lesions seen in infected birds included tracheitis and pneumonia, which correlate with the sites of isolation. Sixty-one percent of the isolations were made from the trachea and 25% from the lung. Age of infected birds ranged from 35 to 315 days in turkeys and 53 days to 3 yr in chickens. In most instances (90%), other bacteria were also isolated from affected sites. The significance of this organism in respiratory disease in birds is unknown.

Infraorbital sinusitis associated with Pasteurella multocida in pen-raised ring-necked pheasants.

Pasteurella multocida, somatic serotype 6, was isolated from the infraorbital sinuses of 8-wk-old ring-necked pheasants with severe sinusitis. In addition, Escherichia coli, Pasteurella haemolytica-like bacteria, Mycoplasma gallinaceum, and Mycoplasma glycophilum were also isolated from some of the sinuses. Clinical signs appeared 3 days after placement on the grow-out ranch. The sinusitis consisted of severe unilateral or bilateral distention of the sinuses by mucoid to caseous exudate. Mortality and morbidity were low. Birds responded to treatment with tetracycline after proper medication procedures. The source of the infection was not determined, though possible sources include the brood ranch, wild animals, or wild waterfowl.

Enhanced recovery of avian influenza virus isolates by a combination of chicken embryo inoculation methods.

Since 1993, 14 cases of avian influenza from four different states in the U.S.A. have been diagnosed by virus isolation from eight avian species. Only 11 of the 14 avian influenza virus (AIV) primary isolations would have been successful if only the standard protocol for AIV isolation, i.e., inoculation of specific-pathogen-free embryonating chicken eggs (ECEs) by the chorioallantoic sac (CAS) route, had been followed. Primary isolation attempts were negative for AIV in three cases in which ECEs were inoculated by the CAS route; AIV could not be detected by hemagglutinating activity, agar gel immunodiffusion test or negative stain electron microscopy. However, in these three cases, primary isolations of AIV were achieved by inoculation of ECEs into either the yolk sac or onto the chorioallantoic membrane.

Morphometric and mechanical properties of femora in young adult male turkeys with and without femoral fractures.

Morphologic and torsional mechanical properties of femora were evaluated in three groups of turkeys to determine whether turkeys that incurred femoral fracture have different radiographic, morphologic, and torsional mechanical properties than do turkeys without femoral fracture, and if body weight was a factor differentiating affected and nonaffected turkeys. Nine turkeys with unilateral femoral fractures and nine turkeys without fractures from Farm A were compared with a group of nine age and genetically matched turkeys from Farm B. Turkeys from Farm A were 10 to 25% heavier (26.2+/-0.9 kg) and turkeys from Farm B were 10% lighter (18.2+/-0.9 kg) than expected breed standards. Femoral length, cortical thickness, medullary diameter, and diaphyseal curvature were measured from craniocaudal and lateromedial radiographs. One intact femur from each of five turkeys with a contralateral femoral fracture (Farm A), nine unaffected turkeys from Farm A, and nine turkeys from Farm B were subjected to failure in a torsion test. Geometric and mechanical results were compared. Turkeys from Farm A had a thicker cortex and a smaller medullary diameter than turkeys from Farm B. Turkeys from Farm A had significantly lower torsional stiffness and failure torque values compared with turkeys from Farm B, when differences in body weight were accounted for (analysis of covariance, P < 0.05). Mechanical failure torque calculated from geometric values suggests that organic or inorganic material arrangement and composition may be responsible, in part, for differences between groups. Femoral fractures may be associated with insufficient skeletal adaptation to heavy body weight.