Abstract
Production losses from abortions, stillbirths, and early calf mortality were described for the 2002 calf crop in 203 beef herds in western Canada. A total of 1689 calves were examined. A summary diagnosis was reported for 64% of aborted calves, 78% of stillborn calves, 88% of neonatal calves, and 94% of the calves > 3 d of age. Diagnoses for aborted calves included: thyroid gland lesions, pneumonia, developmental anomalies, placentitis, and myocardial necrosis or myopathy. For stillborn calves, diagnostic findings included: dystocia, thyroid gland lesions, myocardial necrosis or myopathy, developmental anomalies, and skeletal myopathy or necrosis. The most common diagnoses for neonatal calves (≤ 3 d) were: pneumonia, skeletal myopathy or necrosis, myocardial necrosis or myopathy, accident or trauma, and septicemia. For older calves (3 d to 3 mo), the most common diagnoses included: starvation, abomasal ulcer or perforation, enteritis or colitis, pneumonia, and intestinal volvulus, obstruction, or perforation.
Résumé
Résultats des examens macroscopiques et histologiques des cas d’avortements et de mortalités de veaux dans les troupeaux de bovins de l’Ouest canadien. Les pertes de production attribuables aux avortements, aux mortinatalités et à la mortalité précoce des veaux ont été décrites pour la récolte de veaux de 2002 chez 203 troupeaux de bovins de l’Ouest canadien. Un total de 1689 veaux ont été examinés. Un diagnostic sommaire a été signalé pour 64 % des veaux avortés, 78 % des veaux morts-nés, 88 % des veaux nouveau-nés et 94 % des veaux âgés de > 3 jours. Les diagnostics des veaux avortés incluaient : lésions de la glande thyroïde, pneumonie, anomalies du développement, placentite et nécrose myocardique ou myopathie. Pour les veaux nouveau-nés, les constatations diagnostiques incluaient : dystocie, lésions de la glande thyroïde, nécroses myocardiques, anomalies du développement et myopathie ou nécrose squelettique. Les diagnostics les plus communs pour les veaux néonataux (≤ 3 jours) étaient : pneumonie, myopathie ou nécrose squelettique, accident ou traumatisme et septicémie. Pour les veaux plus âgés (de 3 jours à 3 mois), les diagnostics les plus communs incluaient : inanition, ulcère ou perforation de l’abomasum, entérite ou colite, pneumonie et volvulus, obstruction ou performation intestinale.
(Traduit par Isabelle Vallières)
Introduction
Despite the long history of cattle production in North America, important questions remain about the causes of calf loss in beef herds. Studies examining calf deaths using mail-out questionnaires and interviews have been reported where the findings are limited to a producer-made diagnosis based on history and clinical signs (1–4). While published surveys from diagnostic laboratory findings often include gross postmortem and histologic findings as well as other laboratory test results (5–9), these reports may not be representative of routine herd losses. The cost of testing often limits laboratory submissions to cases that appear unusual or to situations where extreme losses have occurred.
Four peer-reviewed North American studies have examined some submissions from beef herds. Two retrospective laboratory studies summarized the combined findings from more than 11 000 abortions and stillbirths from South Dakota and the surrounding states (7,8). These studies examined large numbers of cases but were limited by available diagnostic resources per case and the testing technology available at the time. The laboratory reported a diagnosis in 35% (7) and 33% (8) of the cases examined. Smaller summaries of dairy and beef abortion submissions between 1993 and 1995 from Ontario (n = 1019) (5) and between 1990 and 2001 from Atlantic Canada (n = 234) (6) reported diagnostic success rates from 29.5% to 41.0%. Only 1 study reported data from calves born alive and these results were not separated from calves that died at birth (n = 31) (6). There were no studies that clearly documented the pathology associated with calf loss in the North American beef industry.
The objective of this study was to acquire information on abortion and age-related patterns of mortality among beef calves in western Canada and to compare findings with available descriptions of calf death and abortion in North America. In the first step of this study, all gross postmortem and histologic examination findings were summarized for calves lost from 203 cow-calf herds during the 2002 calving season. In the second step, a single summary diagnosis (etiologic or morphologic) was reported for each animal after reviewing the history and all examination findings, as well as information from ancillary testing.
Materials and methods
Herd recruitment and data collection
Herds were recruited as a part of a comprehensive study of factors affecting beef cattle productivity in western Canada (10). Investigators invited veterinarians from private clinics across Alberta, Saskatchewan, and northeastern British Columbia to participate. Within each practice, herds were eligible for enrollment based on completeness of animal identification, existing calving records, presence of animal handling facilities, and a relationship with a local veterinary clinic. Herds of < 50 animals and herds not using a winter/spring calving season were excluded from the study to target data collection from cattle raised under conditions most typical of the national beef herd (10).
All calf production losses were summarized for each herd for the complete 2002 calving season, which was defined as December 1, 2001 to November 30, 2002. Abortions before December 1, 2001 were included if the calf, had it survived to full-term, would have been part of the 2002 calf crop. Only calves that were part of the 2002 calf crop and died, or were aborted before May 31, 2002, were eligible for a postmortem examination and inclusion in subsequent analysis. More than 97.9% of all full-term calves from the 2002 calving season were born in these herds between January 1 and May 31, 2002. For every abortion and calf death, participants were asked to record the date and cow identification, and to contact their veterinary clinic to arrange for a necropsy.
Participating veterinarians were supplied with training materials that described the collection and preparation of tissues and with all necessary supplies for sample submission. A standard set of tissues was requested from every case for histologic examination (Table 1). However, the protocol also permitted submission of additional tissues as deemed appropriate based on the necropsy findings. Tissues from excessively autolyzed or scavenged carcasses were not submitted for histopathologic examination. The veterinarian completed a form detailing the history, date of abortion or death of the calf, duration of illness (if noted), condition of the carcass, stage of fetal development or age of the calf, and relevant gross postmortem findings. Each case was uniquely identified to provide consistent linkage between laboratory findings and the herd records for the calf and its dam.
Table 1.
Tissues requested for histologic examination and those received on or before May 31, 2002 (Total submissions from all postmortem examinations, n = 1689 from N = 201 herds; abortions, n = 183; stillbirths, n = 560; neonates, n = 388; calves > 3 d of age, n = 558)
| Organ system | Tissue | Age category |
|||
|---|---|---|---|---|---|
| Abortions | Stillbirths | Calves born alive |
|||
| Neonates | Older calves | ||||
| Respiratory | Lunga | 96.2% (176) | 98.6% (552) | 98.2% (381) | 97.7% (545) |
| Tracheab | 45.9% (84) | 78.9% (442) | 88.4% (343) | 93.4% (521) | |
| Immune | Thymusa | 92.9% (170) | 94.3% (528) | 88.9% (345) | 79.6% (444) |
| Peyer’s patchesb | 78.7% (144) | 91.8% (514) | 89.7% (348) | 90.5% (505) | |
| Lymph nodea | 84.2% (154) | 96.3% (539) | 98.5% (382) | 96.2% (537) | |
| Spleena | 86.9% (159) | 95.9% (537) | 97.4% (378) | 96.4% (538) | |
| Nervous | Any nervous tissuec | 92.3% (169) | 98.6% (552) | 99.7% (387) | 98.7% (551) |
| Braina | 92.3% (169) | 98% (549) | 99.5% (386) | 98.0% (547) | |
| Spinal cordb | 48.1% (88) | 83.6% (468) | 88.7% (344) | 95.2% (531) | |
| Sciatic nerveb | 27.9% (51) | 55.0% (308) | 62.9% (244) | 83.3% (465) | |
| Muscle | Hearta | 96.7% (177) | 97.5% (546) | 98.7% (383) | 97.8% (546) |
| Skeletal musclea | 97.3% (178) | 99.1% (555) | 98.7% (383) | 98.0% (547) | |
| Eyelidd | 84.7% (155) | 64.5% (361) | 39.4% (153) | 11.5% (64) | |
| Alimentary | Duodenumb | 42.1% (77) | 76.3% (427) | 86.1% (334) | 90.5% (505) |
| Jejunumb | 52.5% (96) | 80.9% (453) | 90.7% (352) | 93.5% (522) | |
| Ileuma | 78.7% (144) | 91.8% (514) | 89.7% (348) | 90.5% (505) | |
| Spiral colon/colonb | 50.3% (92) | 81.8% (458) | 90.7% (352) | 93% (519) | |
| Other | Skinb | 12.6% (23) | 37.1% (208) | 69.6% (270) | 93.5% (522) |
| Placentad | 29.0% (53) | 16.4% (92) | 3.4% (13) | 0.2% (1) | |
| Femura | 89.6% (164) | 84.6% (474) | 68.8% (267) | 25.6% (143) | |
| Thyroida | 74.9% (137) | 83.6% (468) | 86.1% (334) | 80.6% (450) | |
| Livera | 92.3% (169) | 97.9% (548) | 98.2% (381) | 96.8% (540) | |
| Kidneya | 89.1% (163) | 98.0% (549) | 98.5% (382) | 96.4% (538) | |
Tissues requested from all age categories.
Tissues requested from full-term live births only.
Included calves with at least 1 lesion in 1 of: brain, spinal cord, or sciatic nerve.
Tissues requested from abortions and stillbirths only.
Laboratory analysis and diagnosis
Tissue samples, fixed in 10% buffered formalin, were submitted to a diagnostic laboratory (Prairie Diagnostic Services Inc., Saskatoon, Saskatachewan). Fixed tissues were trimmed, processed routinely, stained with hematoxylin and eosin (11), and submitted to 1 veterinary pathologist [EGC, Diplomate, American College of Veterinary Pathologists (ACVP)] for examination. The laboratory personnel and pathologist received the history (including stage of development or age category) and necropsy results, but not the geographic location and herd identification. Every submitted tissue was evaluated for histologic abnormalities. An immunohistochemistry (IHC) screening test for bovine viral diarrhea virus (BVDV) was applied to sections of formalin-fixed heart, skin, ileum, kidney, and lung from each case (12).
Additional histochemical (HC) and IHC stains were used at the pathologist’s discretion to aid in establishing a diagnosis. Special stains were used to demonstrate; the presence of mineralization (Alizarin and Von Kossa stains); lipofuscin (Fontana Masson); integrity of the axon (Holmes Silver Stain); extracellular fibrin, elastic fibres, collagen, myelin, intracellular engulfed material (HOPS — Hematoxylin Orcein Phloxine Saffron); myelin (Luxol Fast Blue); carbohydrate and glyco-protein (PAS — Periodic Acid Scheff’s stain); ferric iron (Perl’s stain); hemosiderin (Prussian Blue stain); fibrin and myofibers (PTAH — Phosphotungstic Acid Hematoxylin); and reducing substances (Schmorl’s stain).
Data summary and analysis
Data were maintained in a relational database (Microsoft Access; Microsoft Corporation, Redmond, Washington, USA). Each case was classified as 1 of 3 stages of development: 1) An abortion was defined as the remains of a fetus judged to be at least 1 mo before full term. 2) A stillbirth was defined as a full-term calf (at least 8 mo gestation) that died at or within 1 h of birth, or a calf that was found dead, had not been observed alive, and was obviously recently born (10). This definition relied on the history provided by the herd owner and was intended to include calves that were born weak and died immediately after birth. This definition was also intended to account for the uncertainty in classification that would be expected because not all calvings were observed by the herd owners. 3) Live-born calf mortalities were defined as calves that lived for at least 1 h but died before weaning. These calves were further divided into 2 age categories for subsequent analysis. Neonatal calf mortality referred to a full-term calf that died between 1 h and the end of the 3rd day after birth, while older calf mortality referred to a full-term calf that died between the beginning of the 4th day after birth and weaning.
For each cow in participating herds, data were available on the date of calving, the calving outcome (abortion, stillbirth, or live calf), and whether assistance was provided at calving. Cases were linked to their dam’s record, and assistance at calving, where reported, was described as an easy pull (calving assistance with a minimal amount of necessary traction), a hard pull, a malpresentation, or a caesarean section. Individual animal inventory and death loss records for each herd were used to describe the frequency of calf loss for each stage of development or age category. Herd abortion risk (or cumulative incidence) was defined as the number of abortions expressed as a proportion of the number of pregnant cows retained after pregnancy testing where the pregnancy outcome was known. For the purposes of total herd risk calculations, abortions also included assumed calf losses when the cow was diagnosed as pregnant but failed to calve. The herd veterinarian determined pregnancy status by transrectal palpation in fall 2001, typically between September and November, when most cows were between 2 and 6 mo into gestation. The herd risk of calf loss was described for stillbirths and for calves born alive that died later as the number of cases in each age category divided by the total number of animals at risk or alive at the beginning of the age category. The proportion of all losses submitted for examination, and proportion of cases where the requested tissues were submitted were also summarized to evaluate herd owner and veterinarian compliance with the study protocol.
The following steps were used to assign a summary diagnosis to each case. First, the history was considered and the cases were described based on the lesions identified during gross postmortem examination. All necropsy findings were first summarized as reported by the participating local veterinarians including the interpretations on the field reports. Second, cases were described by the pathologist based on the presence of any histologic lesions and the results of any ancillary testing. Following this second step, all of the diagnoses reported by the pathologist were summarized for each case. Although not considered a lesion, the frequency of autolysis was examined to indicate the condition of the submitted tissues. These reported diagnoses considered all the available information for the animal.
In the final step, a single summary etiologic diagnosis was reported for each animal. Where an etiologic diagnosis could not be determined, a single summary morphologic diagnosis was reported. The single summary diagnosis considered the history, necropsy findings, histologic examination, and any additional laboratory results.
A summary diagnosis of “dystocia” was reported where there was a history of a hard pull or caesarean section with gross evidence of trauma consistent with calving difficulty or where there was a history of malpresentation or an easy pull with no other gross or histologic lesions clearly indicating an alternate summary diagnosis. A summary diagnosis of “trauma” was reported when there were gross or histological lesions reasonably expected to result from physical injury that were not related to a history of dystocia. Some examples include fractured bones, severe bruising or internal hemorrhage not associated with another disease process. “Starvation” was diagnosed based on necropsy findings supported by the absence of or depletion of body fat on histological examination. Starvation was listed as the summary diagnosis when there were no other substantial active lesions sufficient to be considered as a potential cause of death; however, in some cases there was evidence of other preceding disease problems suggesting that the loss of body fat was potentially secondary to another predisposing factor. “Hypothermia and exposure” was diagnosed when the history or gross postmortem comments indicated that cold weather was a factor and no other substantial lesions were identified. Cases received a summary diagnosis of “undetermined” where there were no substantial lesions or indications in the history that could explain the loss of the calf.
Data analysis
All descriptive statistics were calculated using a commercial spreadsheet program (Microsoft Excel; Microsoft Corporation). The agreement between veterinary and laboratory diagnoses was estimated using the kappa coefficient (Stata/SE 10.1 for Windows; StataCorp LP, College Station, Texas, USA).
Results
Study population and compliance in sample submission
During the 2002 calving season, 29 713 cows from 203 herds were observed from pregnancy testing to calving. The risk of loss ranged from 1.6% for aborted fetuses to 4% for live-born calves (Table 2). The submission rate for eligible cases was lowest for abortions and highest for live-born calves (Table 2). Of the examined cases, 3 aborted fetuses, 3 stillborn calves, and 5 live-born calves were too autolyzed or scavenged to warrant submission of tissues to the diagnostic laboratory. Thus, tissues from 180 aborted fetuses, 557 stillbirths, and 941 calves were submitted to the laboratory for histologic examination. Compliance by local veterinarians in submitting tissues was good (Table 1). Tissue submission rates were higher from necropsies of older calves than for fetuses or stillbirths.
Table 2.
Age-specific mortality risk for 2002 calf cropa
| Age category | Cases reported/ animals at risk in 2002 calving seasonb | Cumulative risk | Cases submitted/ cases eligible for postmortemc | Percent submitted |
|---|---|---|---|---|
| Abortion | 479/29 713 cows | 1.6% | (163)d/472 | 35% |
| Stillbirth | 791/29 970 calves | 2.6% | 560/774 | 72% |
| Calves born alive | 1155/29 179 calves | 4.0% | 946/1011 | 94% |
Based on all calving records collected from 203 participating herds.
The 2002 calving season is based on full-term calvings from December 1, 2001 to November 30, 2002 and includes all abortions following the 2001 breeding season. Data based on calving records maintained by herd owners.
Calves that were aborted or died before June 1, 2002 were eligible for a postmortem examination.
Twenty of 183 fetuses were collected for examination from cows that died and were not counted in the calculation of the abortion risk for the study.
Cow breeds were typical of western Canadian beef herds and were classified as primarily British (including Hereford and Angus) — 43.5%, primarily continental (including Simmental, Charolais, Limousin, and Salers) — 48.2%, crosses of British and continental breeds — 7.7%, and other breeds (dairy breeds, Texas Longhorn and other minor breeds) — 0.6%.
Calf sex was reported for > 85% of submissions. Of cases with a reported sex, males were more common than females [aborted, 51% (80/157); stillbirth, 54% (276/511); live-born calves, 58% (508/883)]. Twenty percent (36/183) of aborted fetuses were twins, as were 27% (151/560) of stillborn calves and 8% (75/946) of live-born calves. Based on the information from the calving records and postmortem examination reports, 11% (20/183) of the aborted calves, 50% (279/560) of the stillborn calves, and 17% (157/946) of the live-born calves were assisted at birth. Of the live-born calves examined postmortem, the median age at death was 9 d (25th percentile, 2 d; 75th percentile, 25 d); 95% of the calves examined died before they were 2 mo old. The oldest calf examined was 107 d at the time of death.
Summary of postmortem examination and histopathology findings
Aborted fetuses
Necropsy findings
Over half of the aborted fetuses had no visible lesions on gross postmortem examination and, excluding autolysis and scavenged, the most common gross pathologic diagnoses reported by veterinarians were developmental anomalies (Table 3).
Table 3.
Gross postmortem examination findings reported by private veterinary clinics in aborted fetuses, stillborn, and liveborn beef calves (n = 1689)
| Major morphologic diagnosisa | Age category |
|||
|---|---|---|---|---|
| Abortions | Stillbirths | Calves born alive |
||
| Neonates | Older calves | |||
| Abomasal perforation | 9.9% (55) | |||
| Abomasal torsion | 3.9% (22) | |||
| Abomasal ulcer | 0.5% (2) | 3.8% (21) | ||
| Abomasitis | 2.3% (9) | 2.5% (14) | ||
| Anasarca | 2.2% (4) | 0.2% (1) | ||
| Anemia | 0.8% (3) | 1.6% (9) | ||
| Arthritis | 1.0% (4) | 3.6% (20) | ||
| Ascites | 7.7% (14) | 1.4% (8) | 0.4% (2) | |
| Aspiration pneumonia | 4.1% (16) | 0.7% (4) | ||
| Autolytic tissues | 20.2% (37) | 9.3% (52) | 2.8% (11) | 2.5% (14) |
| Cardiomegaly | 0.9% (5) | 2.8% (11) | 1.3% (7) | |
| Cardiomyopathy | 1.3% (7) | |||
| Developmental anomalies | 10.4% (19) | 6.4% (36) | 10.3% (40) | 3.2% (18) |
| Dehydration | 3.1% (12) | 14.5% (81) | ||
| Diarrhea/enteritis/colitis | 3.4% (13) | 16.1% (90) | ||
| Epicardial hemorrhage | 2.1% (12) | 2.8% (11) | 1.4% (8) | |
| Frost bite | 2.0% (11) | |||
| Hemoperitoneum | 0.9% (5) | 1.0% (4) | ||
| Hemothorax | 2.3% (13) | 0.5% (2) | 0.4% (2) | |
| Hepatic abscesses | 1.6% (9) | |||
| Hepatitis | 1.6% (3) | 1.3% (7) | 0.9% (5) | |
| Hepatomegaly | 1.4% (8) | 1.5% (6) | 1.8% (10) | |
| Intestinal torsion | 4.5% (25) | |||
| Lymphadenopathy | 2.5% (14) | 2.6% (10) | 10.4% (58) | |
| Meningeal congestion/hemorrhage | 3.1% (12) | 1.8% (10) | ||
| Meningitis | 2.2% (12) | |||
| Multisystemic hemorrhage | 0.5% (3) | 2.1% (8) | 0.4% (2) | |
| Neoplasia | 0.5% (1) | |||
| No visible lesions | 53.0% (97) | 57.3% (321) | 39.7% (154) | 13.4% (75) |
| Omphalitis | 3.9% (15) | 7.9% (44) | ||
| Pericarditis | 2.2% (4) | 1.0% (4) | 4.1% (23) | |
| Perirenal hemorrhage | 2.7% (5) | 1.6% (9) | 1.0% (4) | 0.9% (5) |
| Peritonitis | 3.9% (15) | 15.6% (87) | ||
| Placentitis | 0.5% (1) | 0.2% (1) | ||
| Pleuritis | 1.1% (2) | 1.1% (6) | 3.1% (12) | 4.1% (23) |
| Pneumonia | 2.0% (11) | 9.5% (37) | 16.7% (93) | |
| Pulmonary edema | 3.4% (19) | 6.2% (24) | 2.3% (13) | |
| Pulmonary hemorrhage | 2.1% (8) | 1.1% (6) | ||
| Renal disease | 1.1% (2) | 0.7% (4) | 0.5% (2) | 2.3% (13) |
| Rumenitis | 1.8% (7) | 0.9% (5) | ||
| Scavenged | 7.7% (14) | 1.3% (7) | 1.5% (6) | 2.5% (14) |
| Starvation | 0.8% (3) | 11.3% (63) | ||
| Subcutaneous edema/hemorrhage | 6.3% (35) | 3.1% (12) | 0.5% (3) | |
| Thyroid hypertrophy | 0.5% (1) | 3.8% (21) | 2.6% (10) | 0.9% (5) |
| Trauma | 1.1% (2) | 2.1% (12/560) | 10.8% (42/388) | 6.1% (34/558) |
Other diagnoses were reported; however, examples of diagnoses where only 1 or 2 cases were reported are not summarized here.
Histologic examination findings
The most commonly reported histologic lesions involved the thyroid gland (Table 4). The next most common lesions involved inflammatory processes, namely placentitis and subsequent lung changes induced by inhalation of bacteria and other debris associated with placentitis. Bacteria were visible in 4 of the 14 cases of placentitis. Mycotic elements were present in 2 cases, and 4 cases were attributed to mycotic infection based on histologic lesions. There was 1 case of Sarcosporidia spp. and in 3 cases no infectious organisms were identified.
Table 4.
Histologic examination or confirmation results reported by a veterinary pathologist for aborted fetuses (n = 180), stillborn (n = 557) and liveborn beef calves (neonates, n = 387; calves > 3 d of age, n = 554)
| Major morphologic diagnosis | Age category |
|||
|---|---|---|---|---|
| Abortions | Stillbirths | Calves born alive |
||
| Neonates | Older calves | |||
| Abomasal torsion | 0.0% (0/1) | 0.0% (0/7) | 0.0% (0/10) | 1.4% (1/74) |
| Abomasal ulcer | 0.0% (0/1) | 0.0% (0/7) | 0.0% (0/10) | 18.9% (14/74) |
| Abomasitis | 0.0% (0/1) | 0.0% (0/7) | 0.0% (0/10) | 4.1% (3/74) |
| Anemia | 0.0% (0/180) | 0.0% (0/557) | 0.3% (1/387) | 0.9% (5/554) |
| Autolysisa | 8.9% (16/180) | 5.2% (29/557) | 1.8% (7/387) | 2.5% (14/554) |
| Bacterial infection (multi-site) or septicaemia | 1.1% (2/180) | 0.2% (1/557) | 8.8% (34/387) | 4.7% (26/554) |
| Cerebral edema | 1.8% (3/169) | 2.6% (14/549) | 7.3% (28/386) | 3.3% (18/547) |
| Coccidiosis | 0.0% (0/92) | 0.0% (0/458) | 0.0% (0/352) | 1.2% (6/519) |
| Developmental anomaly | 8.3% (15/180) | 5.0% (28/557) | 7.8% (30/387) | 2.3% (13/554) |
| Disseminated intravascular coagulationb | 7.8% (14/180) | 2.9% (16/557) | 13.2% (51/387) | 16.2% (90/554) |
| Encephalitis | 0.6% (1/169) | 0.4% (2/549) | 0.5% (2/386) | 2.2% (12/547) |
| Enteritis, colitis, or typhlytis | 0.6% (1/160) | 0.9% (5/544) | 6.5% (25/383) | 24.0% (131/545) |
| Fungal infection | 2.2% (4/180) | 0.2% (1/557) | 0.3% (1/387) | 0.7% (4/554) |
| Growth arrest lattices of femur | 12.8% (21/164) | 2.3% (11/474) | 3.0% (8/267) | 6.3% (9/143) |
| Hemorrhage (microscopic) | 3.9% (7/180) | 18.9% (105/557) | 24.3% (94/387) | 15.2% (84/554) |
| Hemosiderosis of liver | 8.3% (14/169) | 28.1% (154/548) | 30.4% (116/381) | 12.6% (68/540) |
| Hepatic abscesses | 0.0% (0/169) | 0.0% (0/548) | 0.0% (0/381) | 0.9% (5/540) |
| Hepatic necrosis/fibrosis | 1.8% (3/169) | 0.4% (2/548) | 1.6% (6/381) | 2.6% (14/540) |
| Hypomyelination | 1.2% (2/169) | 3.8% (21/552) | 7.5% (29/387) | 5.6% (31/551) |
| Infectious bovine rhinotracheitis | 1.1% (2/180) | 0.0% (0/557) | 0.0% (0/387) | 0.0% (0/554) |
| Intestinal torsion | 0.0% (0/180) | 0.0% (0/557) | 0.3% (1/387) | 0.2% (1/554) |
| Meningoencephalitis | 0.6% (1/169) | 0.2% (1/549) | 0.3% (1/386) | 0.2% (1/547) |
| Meningitis | 0.0% (0/169) | 0.2% (1/549) | 2.8% (11/386) | 3.5% (19/547) |
| Myocardial necrosis or degenerative myopathyc | 9.0% (16/177) | 15.4% (84/546) | 24.3% (93/383) | 19.6% (107/546) |
| Myocarditis | 4.0% (7/177) | 0.2% (1/546) | 0.8% (3/383) | 0.5% (3/546) |
| Nephritis | 1.2% (2/163) | 0.0% (0/549) | 0.5% (2/382) | 5.0% (27/538) |
| No histologic lesionsd | 20.0% (36/180) | 14.2% (79/557) | 3.4% (13/387) | 4.3% (24/554) |
| Omphalitis | 0.0% (0/180) | 0.0% (0/557) | 0.3% (1/387) | 1.1% (6/554) |
| Passive congestion (of lung/liver) | 1.1% (2/180) | 2.5% (14/557) | 1.0% (4/387) | 3.2% (18/554) |
| Pericarditis | 0.6% (1/177) | 0.0% (0/546) | 0.5% (2/383) | 1.3% (7/546) |
| Peritonitis | 0.0% (0/180) | 0.0% (0/557) | 1.3% (5/387) | 6.5% (36/554) |
| Placentitis | 26.4% (14/53) | 8.7% (8/92) | 7.7% (1/13) | 0.0% (0/1) |
| Pleuritis | 0.6% (1/176) | 0.0% (0/552) | 1.0% (4/381) | 2.0% (11/545) |
| Pneumonia | 22.2% (39/176) | 5.8% (32/552) | 24.4% (93/381) | 17.8% (97/545) |
| Renal oxalosis | 3.7% (6/163) | 0.4% (2/549) | 0.5% (2/382) | 0.4% (2/538) |
| Renal tubular necrosis | 0.6% (1/163) | 0.0% (0/549) | 0.3% (1/382) | 1.3% (7/538) |
| Skeletal degenerative myopathy or necrosisc | 5.6% (10/178) | 20.2% (112/555) | 46.2% (177/383) | 40.2% (220/547) |
| Splenic hyperplasia | 2.5% (4/159) | 0.0% (0/537) | 0.0% (0/378) | 0.4% (2/538) |
| Starvation | 0.0% (0/180) | 0.0% (0/557) | 6.2% (24/387) | 29.4% (163/554) |
| Thymic atrophy | 14.7% (25/170) | 6.1% (32/528) | 19.7% (68/345) | 35.1% (156/444) |
| Thyroid lesion | 29.9% (41/137) | 38.5% (180/468) | 28.7% (96/334) | 19.1% (86/450) |
At least 1 of the tissues examined was coded as severely autolyzed during histologic examination.
Histopathologic changes consistent with or suggestive of disseminated intravascular coagulation.
Some tissues had evidence of both myopathy and necrosis.
No histologic findings of any type. Terminal aspiration of meconium was not considered to be a lesion nor was bacterial overgrowth.
Summary of developmental anomalies
Developmental anomalies were listed after review of the submitted information and histologic examination in 15 aborted fetuses; 2 cases had more than 1 anomaly. Reported anomalies included umbilical hernias (n = 6), cranial deformities such as hydrocephalus (n = 5), hamartomas of the lung, skeletal muscles, and tracheal rings (n = 2), segmental atresia of the alimentary tract (n = 2), chondrodysplasia (n = 1), and hypotrichosis (n = 1).
Additional testing
BVDV antigens were detected by IHC in the tissues of 4 fetuses; 1 of these fetuses had a developmental anomaly (hypotrichosis). The liver of 1 fetus with histologic lesions of multifocal hepatic necrosis contained antigens for infectious bovine rhinotracheitis (IBR) virus detected by IHC. A second fetus was diagnosed with IBR based only on typical histologic findings. Neosporum caninum was not detected in any of the fetuses.
Summary diagnosis
A summary diagnosis was identified in 64% of the aborted fetuses (Table 5). The most common diagnoses described for aborted calves included thyroid gland lesions, pneumonia, developmental anomalies, placentitis, and myocardial necrosis or myopathy (Tables 4 and 5).
Table 5.
Summary diagnosis for 183 fetusesa based on history, field necropsy findings, and histologic examination
| Final diagnosis | Percent with lesions | Skeletal muscle degenerative myopathy or necrosis | Myocardial degenerative myopathy or necrosis | Thyroid gland lesion | Pneumonia | Enteritis |
|---|---|---|---|---|---|---|
| Undetermined | 35.5% (65) | 3.3% (2/61) | 1.7% (1/59) | 10.0% (4/40) | 5.1% (3/59) | 0.0% (0/52) |
| Cow died with fetus in utero | 10.9% (20) | 0.0% (0/20) | 10.0% (2/20) | 17.6% (3/17) | 5.0% (1/20) | 0.0% (0/18) |
| Thyroid gland lesion | 10.4% (19) | 0.0% (0/19) | 10.5% (2/19) | 100% (19/19) | 5.6% (1/18) | 0.0% (0/18) |
| Pneumonia | 10.4% (19) | 5.3% (1/19) | 0.0% (0/19) | 14.3% (2/14) | 100% (19/19) | 0.0% (0/17) |
| Developmental anomaly | 6.0% (11) | 9.1% (1/11) | 0.0% (0/11) | 37.5% (3/8) | 9.1% (1/11) | 0.0% (0/10) |
| Placentitisb | 6.0% (11) | 0.0% (0/10) | 9.1% (1/11) | 25.0% (2/8) | 45.5% (5/11) | 0.0% (0/9) |
| Myocardial necrosis/myopathy | 3.8% (7) | 14.3% (1/7) | 100% (7/7) | 40.0% (2/5) | 14.3% (1/7) | 0.0% (0/7) |
| Bovine viral diarrhea virus | 2.2% (4) | 25.0% (1/4) | 0.0% (0/4) | 50.0% (2/4) | 0.0% (0/4) | 0.0% (0/4) |
| Disseminated intravascular coagulationc | 2.2% (4) | 50.0% (2/4) | 0.0% (0/4) | 33.3% (1/3) | 50.0% (2/4) | 0.0% (0/4) |
| Lympholysis, multiple | 2.2% (4) | 0.0% (0/4) | 0.0% (0/4) | 0.0% (0/2) | 0.0% (0/4) | 0.0% (0/4) |
| Myocarditis | 2.2% (4) | 0.0% (0/4) | 50.0% (2/4) | 0.0% (0/3) | 50.0% (2/4) | 0.0% (0/4) |
| Heart failure | 1.6% (3) | 0.0% (0/3) | 33.3% (1/3) | 0.0% (0/3) | 66.7% (2/3) | 0.0% (0/2) |
| Infectious bovine rhinotracheitis | 1.1% (2) | 0.0% (0/2) | 0.0% (0/2) | 50.0% (1/2) | 0.0% (0/2) | 0.0% (0/2) |
| All other classifications | 5.5% (10) | 20.0% (2/10) | 0.0% (0/10) | 22.2% (2/9) | 20.0% (2/10) | 11.1% (1/9) |
Fetal loss from the 2002 calf crop before 8 mo of gestation examined postmortem. Tissue samples were submitted from 180 of 183 cases.
Either confirmed with placental tissue or lesions consistent with placentitis in the carcass.
Histopathologic changes consistent with or suggestive of disseminated intravascular coagulation.
Twenty fetuses were collected from dead cows. The resulting production loss of the fetuses was attributed to the death of the dam and these fetuses were not included in the calculated abortion risk for the study (Tables 1 and 5). However, 12 of these fetuses had 1 or more lesions identified by gross necropsy or histopathology. In addition to thyroid lesions, heart lesions and pneumonia (Table 5), these cases had growth retardation lattices (GRL) in the femur (n = 2), increased pigmentation of the liver and kidneys (n = 2), lesions of the immune system (n = 2), BVDV detected by IHC (n = 1), and brain necrosis (n = 1). One case was too autolyzed for evaluation.
Stillborn calves
Necropsy findings
The most common gross necropsy observations for stillborn calves were developmental anomalies (Table 3). Lesions of dystocia included subcutaneous edema and hemorrhages (hemothorax, epicardial, and perirenal) and other evidence of trauma, such as fractured ribs, legs, or spine (Table 3).
Histologic examination findings
Lesions were most common in the thyroid gland, liver, and skeletal and cardiac muscles (Table 4). Other common lesions included pneumonia and placentitis (Table 4). The femurs from 2% of cases contained GRL. No histologic lesions were identified in the tissues from 14% of the stillborn calves.
Summary of developmental anomalies
Twenty-eight of 560 stillborn calves had at least 1 congenital defect (Table 4), 5 had 2 defects, and 1 had 4 defects. Developmental anomalies included cranial deformities such as hydrocephalus (n = 10) and cleft palate (n = 2), umbilical hernia (n = 5), cardiac anomalies (n = 4), flexural limb deformities (n = 4), schistosomus reflexus (n = 2), spina bifida (n = 2), spinal deformities (n = 1), anasarca (n = 1), ectromelia (n = 1), hamartoma of the lungs (n = 1), and microencephaly (n = 1).
Additional testing
Histochemical evidence of gram-positive rods was confirmed by IHC examination of the lung and placenta in 1 case, and septicemia due to Listeria spp. in 2 stillbirth cases. BVDV was confirmed by IHC in 1 case and N. caninum was identified using IHC in the placental tissue of another calf.
Summary diagnosis
Dystocia was the most commonly identified summary diagnosis (Table 6). The next most frequent diagnoses were lesions of the thyroid gland or heart muscle. Five stillbirths were attributed to placentitis (Table 6); Listeria spp. was confirmed in 1 case, filamentous elements were observed in 2 cases, and inflammation was noted without identification of a specific pathogen in the remaining 2 cases.
Table 6.
Summary diagnosis for 560 stillborn calvesa based on history, field necropsy findings, and histologic examination
| Final diagnosis | Percent with lesions | Skeletal muscle degenerative myopathy or necrosis | Myocardial degenerative myopathy or necrosis | Thyroid gland lesion | Pneumonia | Enteritis |
|---|---|---|---|---|---|---|
| Dystocia | 40.2% (225) | 13.0% (29/223) | 9.5% (21/221) | 39.9% (77/193) | 3.2% (7/222) | 0.5% (1/221) |
| Undetermined | 21.6% (121) | 5.0% (6/120) | 1.7% (2/116) | 12.2% (10/82) | 2.5% (3/118) | 0.0% (0/115) |
| Thyroid gland lesion | 8.9% (50) | 4.0% (2/50) | 0.0% (0/50) | 100% (50/50) | 0.0% (0/50) | 2.1% (1/48) |
| Myocardial necrosis/myopathy | 7.1% (40) | 82.5% (33/40) | 100% (40/40) | 37.1% (13/35) | 7.5% (3/40) | 0.0% (0/38) |
| Developmental anomaly | 4.3% (24) | 13.0% (3/23) | 8.7% (2/23) | 30.0% (6/20) | 8.7% (2/23) | 0.0% (0/22) |
| Skeletal myopathy/necrosis | 3.6% (20) | 100% (20/20) | 10.0% (2/20) | 41.2% (7/17) | 0.0% (0/19) | 5.0% (1/20) |
| Liver hemosiderosis | 2.7% (15) | 21.4% (3/14) | 0.0% (0/14) | 9.1% (1/11) | 0.0% (0/15) | 0.0% (0/15) |
| Heart failure | 2.1% (12) | 25.0% (3/12) | 91.7% (11/12) | 16.7% (2/12) | 0.0% (0/12) | 0.0% (0/12) |
| Pneumonia | 2.0% (11) | 36.4% (4/11) | 22.2% (2/9) | 30.0% (3/10) | 100% (11/11) | 0.0% (0/11) |
| Disseminated intravascular coagulationb | 1.3% (7) | 28.6% (2/7) | 14.3% (1/7) | 20.0% (1/5) | 28.6% (2/7) | 0.0% (0/7) |
| Cow died with fetus in utero | 0.9% (5) | 0.0% (0/5) | 0.0% (0/5) | 40.0% (2/5) | 20.0% (1/5) | 0.0% (0/5) |
| Placentitisc | 0.9% (5) | 20.0% (1/5) | 0.0% (0/5) | 25.0% (1/4) | 20.0% (1/5) | 0.0% (0/5) |
| Accident/trauma | 0.7% (4) | 50.0% (2/4) | 0.0% (0/4) | 33.3% (1/3) | 0.0% (0/4) | 0.0% (0/4) |
| Exposure/hypothermia | 0.7% (4) | 50.0% (2/4) | 50.0% (2/4) | 0.0% (0/4) | 0.0% (0/4) | 0.0% (0/4) |
| Arteritis | 0.7% (4) | 0.0% (0/4) | 0.0% (0/4) | 0.0% (0/4) | 0.0% (0/4) | 0.0% (0/4) |
| Premature non-viable neonate | 0.7% (4) | 50.0% (2/4) | 33.3% (1/3) | 50.0% (2/4) | 0.0% (0/4) | 0.0% (0/4) |
| All other classifications | 1.6% (9) | 0.0% (0/9) | 0.0% (0/9) | 44.4% (4/9) | 22.2% (2/9) | 22.2% (2/9) |
Death loss from the 2002 calf crop within 1 mo of full term and before 1 h after calving. Tissue samples were submitted from 557 of 560 cases.
Histopathologic changes consistent with or suggestive of disseminated intravascular coagulation.
Either confirmed with placental tissue or lesions consistent with placentitis in the carcass.
Neonatal calves
Necropsy findings
The most common findings were developmental anomalies (Table 3). Gross indications of pneumonia were reported in 10% of neonatal calves. Other evidence of infection or inflammation included omphalitis, peritonitis, diarrhea, pleuritis, abomasitis, rumenitis, arthritis, and peri-carditis (Table 3). Pulmonary edema without gross evidence of pneumonia was reported in 6% of neonatal calves. Evidence of trauma, such as hemorrhage, lacerated internal organs, or fractured ribs, skulls, or long bones, was found in 6% of cases.
Histologic examination findings
The most common lesions included skeletal myopathy or necrosis, hemosiderosis of the liver, thyroid lesions, and myocardial necrosis (Table 4). Histologic evidence of infection or inflammation included pneumonia, bacteremia, septicaemia, enteritis, meningitis, and peritonitis (Table 4). Thymic atrophy was reported in 20% of calves.
Summary of developmental anomalies
Thirty calves had at least 1 developmental anomaly and 3 calves had 2 developmental anomalies. These included segmental atresia of the alimentary tract (n = 8), arthrogryposis and flexural deformity (n = 6), cleft palate (n = 5) and other cranial deformities such as hydrocephalus (n = 4), umbilical hernia (n = 3), anasarca (n = 1), anencephaly (n = 1), Ehlers Danlos Syndrome (n = 1), malformed eyes (n = 1), heart defects (n = 1), osteopetrosis of the femoral diaphysis (n = 1), and patent urachus (n = 1).
Additional testing
Immunohistochemical staining identified 8 calves with persistent BVDV infection, 2 with adenovirus infection, and 1 with Neospora spp. in the spinal cord. One of the calves with BVDV had a developmental anomaly (segmental alimentary tract aplasia).
Summary diagnosis
Compared to aborted fetuses and stillborns, fewer neonatal deaths had an undetermined summary diagnosis and more deaths were attributed to diseases with a probable bacterial or viral etiology including pneumonia, coliform septicemia or multisystemic infection, enteritis and colitis, BVDV, meningitis, and placentitis (Table 7).
Table 7.
Summary diagnosis for 388 neonatal calves up to 3 d of agea based on history, field necropsy findings, and histologic examination
| Final diagnosis | Percent with lesions | Skeletal muscle degenerative myopathy or necrosis | Myocardial degenerative myopathy or necrosis | Thyroid gland lesion | Pneumonia | Enteritis |
|---|---|---|---|---|---|---|
| Undetermined | 11.8% (46) | 20.9% (9/43) | 2.2% (1/45) | 10.3% (4/39) | 0.0% (0/43) | 9.3% (4/43) |
| Pneumonia | 9.8% (38) | 47.4% (18/38) | 15.8% (6/38) | 29.0% (9/31) | 100% (37/37) | 2.7% (1/37) |
| Skeletal myopathy/necrosis | 9.5% (37) | 100% (37/37) | 18.9% (7/37) | 47.1% (16/34) | 0.0% (0/36) | 2.8% (1/36) |
| Myocardial necrosis/myopathy | 8.5% (33) | 69.7% (23/33) | 100% (33/33) | 28.6% (8/28) | 12.1% (4/33) | 3.0% (1/33) |
| Accident/trauma | 8.2% (32) | 33.3% (10/30) | 9.7% (3/31) | 20.7% (6/29) | 9.7% (3/31) | 0.0% (0/32) |
| Septicemia or multisystemic infection | 7.4% (29) | 34.5% (10/29) | 17.2% (5/29) | 23.1% (6/26) | 24.1% (7/29) | 6.9% (2/29) |
| Developmental anomaly | 5.9% (23) | 39.1% (9/23) | 27.3% (6/22) | 21.1% (4/19) | 43.5% (10/23) | 4.3% (1/23) |
| Dystocia | 9.5% (37) | 40.5% (15/37) | 29.7% (11/37) | 25.0% (8/32) | 18.9% (7/37) | 8.1% (3/37) |
| Exposure/hypothermia | 4.6% (18) | 50.0% (9/18) | 16.7% (3/18) | 7.1% (1/14) | 5.9% (1/17) | 5.6% (1/18) |
| Thyroid gland lesion | 4.1% (16) | 25.0% (4/16) | 6.3% (1/16) | 100% (16/16) | 11.8% (2/17) | 0.0% (0/16) |
| Aspiration/aspiration pneumonia | 2.8% (11) | 54.5% (6/11) | 9.1% (1/11) | 55.6% (5/9) | 63.6% (7/11) | 0.0% (0/11) |
| Enteritis/colitis | 2.1% (8) | 25% (2/8) | 12.5% (1/8) | 25% (1/4) | 25.0% (2/8) | 100% (8/8) |
| Disseminated intravascular coagulationb | 2.1% (8) | 37.5% (3/8) | 12.5% (1/8) | 14.3% (1/7) | 12.5% (1/8) | 12.5% (1/8) |
| Bovine viral diarrhea virus | 2.1% (8) | 50.0% (4/8) | 37.5% (3/8) | 42.9% (3/7) | 50.0% (4/8) | 0.0% (0/8) |
| Heart failure | 1.3% (5) | 60.0% (3/5) | 80.0% (4/5) | 40.0% (2/5) | 20.0% (1/5) | 0.0% (0/5) |
| Liver hemosiderosis | 1.0% (4) | 50.0% (2/4) | 33.3% (1/3) | 33.3% (1/3) | 0.0% (0/3) | 0.0% (0/4) |
| Abomasitis/rumenitis | 1.0% (4) | 50.0% (2/4) | 25.0% (1/4) | 0.0% (0/4) | 25.0% (1/4) | 0.0% (0/4) |
| Arteritis | 1.0% (4) | 0.0% (0/4) | 0.0% (0/4) | 0.0% (0/4) | 25.0% (1/4) | 0.0% (0/4) |
| All other classifications | 7.0% (27) | 40.7% (11/27) | 19.2% (5/26) | 20.0% (5/25) | 18.5% (5/27) | 7.4% (2/27) |
Tissue samples were submitted from 99.5% of calves examined that had died between 1 h after birth and 3 d of age.
Histopathologic changes consistent with or suggestive of disseminated intravascular coagulation.
Thirty-two calves had lesions consistent with trauma typical of what would be expected if a cow laid on or stepped on the calf. Many of these calves had additional lesions suggesting that they were compromised prior to being injured (Table 7). Likewise, many neonatal deaths attributed to dystocia, exposure or hypothermia, and aspiration pneumonia, also had lesions of the muscles, heart, or thyroid.
Calves older than 3 days
Necropsy findings
Twenty percent of older calves had lesions of the abomasum, including inflammation (n = 13), ulcers (n = 21), torsion (n = 22), and perforation (n = 55); another 4.5% died with an intestinal volvulus (Table 3). Gross lesions consistent with infection or inflammation were common and included pneumonia, diarrhea, peritonitis (not associated with abomasal ulcers), omphalitis, pericarditis, pleuritis, arthritis, meningitis, and hepatic abscesses (Table 3).
Evidence of dehydration was reported in 15% of calves and starvation in 11%. Evidence of trauma was present in 4% of calves and included bite wounds, and fractures of ribs, metatarsals, mandibles, and a case with fractured skull and femur.
Developmental abnormalities were reported in 3% of calves and 6 calves had more than 1 anomaly.
Histologic examination findings
The most common lesions were in the skeletal muscle, thymus, thyroid, and myocardium (Table 4). The most common lesions of inflammation or infection included enteritis, pneumonia, peritonitis, and meningitis. Histologic evidence of multisystemic infection or septicemia was noted in 4.7% of calves. Pleuritis, pericarditis, and omphalitis were identified in ≤ 2% of the calves (Table 4).
Summary of developmental anomalies
Anomalies were reported by the pathologist in 13 calves (Table 4). One calf had 2 anomalies. The anomalies included heart defects (n = 4), cleft palate (n = 2) or other cranial deformity (n = 2), segmental atresia of the alimentary tract (n = 2), umbilical hernia (n = 2), spinal deformities (n = 1), and cerebellar hypoplasia (n = 1).
Additional testing
Sections of small intestine and colon from 85 calves with histologic evidence of enteritis, colitis, or both were examined using IHC for coronavirus; 53 (62%) tested positive. Tissues from 11 calves (2.0%) were IHC positive for BVDV, 1 was IHC positive for Salmonella, 2 were IHC positive for adenovirus, and the brain and spinal cord from 1 calf was IHC positive for Neospora spp.
Summary diagnosis
Inflammatory conditions, interpreted as evidence of infection, were listed as the summary diagnosis for 31% of the older calves (Table 8). The summary diagnoses included enteritis and colitis, pneumonia, multisystemic infection, and septicemia. These calves often had concurrent skeletal muscle, heart muscle, or thyroid lesions (Table 8).
Table 8.
Summary diagnosis for 558 calves more than 3 d olda based on history, field necropsy findings, and histologic examination
| Final diagnosis | Percent with lesions | Skeletal muscle degenerative myopathy or necrosis | Myocardial degenerative myopathy or necrosis | Thyroid gland lesion | Pneumonia | Enteritis |
|---|---|---|---|---|---|---|
| Starvation | 16.3% (91) | 44.0% (40/91) | 19.8% (18/91) | 13.8% (11/80) | 9.1% (8/88) | 11.0% (10/91) |
| Abomasal ulcer/torsion/perforation | 11.6% (65) | 20.6% (13/63) | 9.5% (6/63) | 10.0% (5/50) | 4.8% (3/63) | 7.8% (5/64) |
| Enteritis/colitis | 11.1% (62) | 40.0% (24/60) | 19.4% (12/62) | 17.3% (9/52) | 14.5% (9/62) | 91.9% (57/62) |
| Pneumonia | 6.3% (35) | 52.9% (18/34) | 22.9% (8/35) | 25.9% (7/27) | 100% (35/35) | 11.4% (4/35) |
| Undetermined | 6.1% (34) | 18.8% (6/32) | 6.7% (2/30) | 4.8% (1/21) | 0.0% (0/30) | 3.7% (1/27) |
| Other intestinal (torsion/obstruction/volvulus) | 5.2% (29) | 20.7% (6/29) | 17.2% (5/29) | 11.1% (2/18) | 0.0% (0/29) | 24.1% (7/29) |
| Multisystemic infection | 5.0% (28) | 60.7% (17/28) | 22.2% (6/27) | 35.0% (7/20) | 46.4% (13/28) | 53.6% (15/28) |
| Skeletal myopathy/necrosis | 4.3% (24) | 100% (24/24) | 29.2% (7/24) | 43.5% (10/23) | 13.0% (3/23) | 4.2% (1/24) |
| Accident/trauma | 4.1% (23) | 39.1% (9/23) | 13.6% (3/22) | 27.8% (5/18) | 13.6% (3/22) | 17.4% (4/23) |
| Abomasal torsion (no ulcer) | 3.6% (20) | 26.3% (5/19) | 10.0% (2/20) | 23.5% (4/17) | 15% (3/20) | 20.0% (4/20) |
| Septicemia | 3.2% (18) | 29.4% (5/17) | 22.2% (4/18) | 17.6% (3/17) | 22.2% (4/18) | 11.1% (2/18) |
| Myocardial necrosis/myopathy | 2.7% (15) | 86.7% (13/15) | 100% (15/15) | 25.0% (3/12) | 0.0% (0/15) | 0.0% (0/14) |
| Heart failure | 2.3% (13) | 38.5% (5/13) | 61.5% (8/13) | 25.0% (2/8) | 15.4% (2/13) | 0.0% (0/13) |
| Disseminated intravascular coagulation | 2.3% (13) | 30.8% (4/13) | 7.7% (1/13) | 30.0% (3/10) | 0.0% (0/13) | 7.7% (1/13) |
| Renal failure | 2.0% (11) | 36.4% (4/11) | 18.2% (2/11) | 0.0% (0/9) | 18.2% (2/11) | 30.0% (3/10) |
| Meningitis/encephalitis | 1.8% (10) | 40.0% (4/10) | 10.0% (1/10) | 20.0% (2/10) | 0.0% (0/10) | 20.0% (2/10) |
| Peritonitis/pleuritis | 1.6% (9) | 22.2% (2/9) | 0.0% (0/9) | 14.3% (1/7) | 22.2% (2/9) | 0.0% (0/9) |
| Developmental anomaly | 1.6% (9) | 33.3% (3/9) | 0.0% (0/9) | 33.3% (2/6) | 22.2% (2/9) | 22.2% (2/9) |
| Bovine viral diarrhea virus | 1.6% (9) | 55.6% (5/9) | 44.4% (4/9) | 12.5% (1/8) | 22.2% (2/9) | 44.4% (4/9) |
| Thyroid gland lesion | 1.3% (7) | 28.6% (2/7) | 0.0% (0/5) | 100% (7/7) | 0.0% (0/6) | 0.0% (0/6) |
| All other classifications | 5.9% (33) | 35.5% (11/31) | 9.7% (3/31) | 3.3% (1/30) | 18.8% (6/32) | 29.0% (9/31) |
Tissue samples were submitted from 99.5% of calves examined that had died between 3 d of age and May 31, 2002.
Starvation was the most common summary diagnosis; however, most of these cases had additional lesions suggesting they were compromised by underlying disease processes (Table 8). Abomasal disease (ulcer, perforation, torsion, or volvulus) was the second most common diagnosis. Intestinal accidents (volvulus, obstruction, perforation) were less common.
Although skeletal muscle, heart muscle, and thyroid gland lesions were common histologic findings, only 46 deaths were directly attributed to these lesions. Other calves were either diagnosed with another more immediate and severe condition, or had such minor lesions that death could not be explained by these findings and the diagnosis was reported as undetermined (Table 8).
Summary of histologic findings for all developmental stages and age categories
The 4 most common histologic lesions across all age categories were: 1) degenerative myopathy or necrosis of skeletal muscles, 2) lesions of the thyroid gland, 3) hemosiderosis of the liver, and 4) necrosis or degenerative myopathy of the myocardium.
Lesions in skeletal muscle including degenerative myopathy (29.4%; 489/1663) and myonecrosis (3.9%; 65/1663) were common. Necrosis was reported if fragmentation of myofibrils was either segmental or diffuse in a longitudinal section of either a single myofiber or a cluster of myofibers. This was confirmed in some cases with PTAH or HOPS stains. Necrosis was also chararacterized by fragmentation of the sarcoplasmic membrane or by the presence of mineralization of fragmented myofibers or inflammatory cells. Mineralization was confirmed in some cases with Van Kossa and Alizarin stains. Degeneration was characterized by the presence of excessively “wavy” myofibers with the appearance of hypercellularity due to increased numbers of sarcoplasmic nuclei or excessive hypercontraction bands. Degeneration was also characterized by the presence of areas of homogeneous light blue staining myofibers or “basophilic degeneration” which did not stain positively for mineralization. Degenerative skeletal myopathy was most common in calves born alive (40.0%; 372/930) and least common in aborted calves (5.6%; 10/178). It was most commonly reported in tongue and diaphragm (62.0%; 424/684) relative to other skeletal muscles and was occasionally diagnosed in eyelids and esophageal muscle.
Thyroid lesions were most common in stillborn calves and were least common in calves that were alive at birth (Table 4). Thyroid lesions were classified into 4 groups: hypoplasia and lack of colloid (8.8%; 123/1389), necrosis and degeneration (13.6%; 189/1389), hyperplasia or goiter (2.7%; 38/1389), and abnormal colloid with no other lesion present (3.8%; 53/1389). Hypoplastic thyroids were comprised of small follicles that contained pale colloid or no colloid and had degenerative changes in the follicular epithelium. Hypoplasia and absence of colloid was more common in stillbirths and abortions than in neonates and older calves. Findings associated with thyroid degeneration or necrosis were most common in neonates and stillbirths and often included, but were not limited to: small and empty follicles, pale colloid, vacuolated follicular epithelium, pyknotic follicular epithelial nuclei, and some epithelial sloughing. Hyperplastic thyroid glands were most common in aborted calves and were characterized by proliferation and hyperplasia of follicular epithelium, in-folding of the epithelium resulting in small luminal size and a decrease in the amount of follicular colloid or absence of follicular colloid. Some cases were classified as showing “colloid goiter” where the thyroid had very flattened epithelium and larger than normal follicles, yet normal looking colloid content. Variation in staining intensity was considered to be due to abnormalities of the colloid because of the consistent appearance of staining of other tissues processed at the same time and with the same staining solutions. Those thyroids with pale colloid also frequently had smaller than normal thyroid follicles.
Hemosiderin was visible microscopically in the liver as yellowish or brown granules which were found in the hepatocytes. This pigment was in the periportal hepatocytes, but in severe cases was present through the hepatic lobules. Presence of this pigment was confirmed and differentiated from lipofuscin by Prussian blue staining, but some of the pigment also partially stained positive with the Schmorl’s stain for lipofuscin.
Histologic lesions in the cardiac muscle were present in all age classes of calves (Tables 4). Changes included hypereosinonphilic myofibers, swollen nuclei, and other degenerative nuclear changes such as karyorrhexis and pyknosis, and focal or coalescing areas of coagulation necrosis. Histochemical stains including PTAH, HOPS, Masson’s trichrome, and PAS were used to verify the diagnosis when necessary. Localized focal, multifocal, and regional patches of acute myocardial necrosis were commonly observed in stillborn calves, neonates, and older calves (Table 4). Degeneration including mineralization of damaged myocardial cells (3.5%; 58/1652) was less frequent than cardiac muscle necrosis (15.4%; 254/1652).
Discussion
This study was unique in both the high proportion of the reported calf death loss from each herd that was examined and in the number of beef herds from western Canada included in the study. The pattern of calf loss reported in these cow-calf herds was consistent with what has been reported in the literature (1–5,9,12). Lesions associated with abortion, stillbirth, neonatal, and older calf deaths were identified that would have been missed without histologic examination of a complete range of tissues. Comprehensive and standardized diagnostic testing was a major strength of this study; however, due to the large number of submissions and substantial distances from farms to the laboratory, labor intensive and time sensitive procedures such as fresh tissue culture were not included in the standard protocol.
Three types of lesions were observed on histologic examination that consistently ranked among the most common summary diagnoses: skeletal myopathy or necrosis, myocardial necrosis or degeneration, and thyroid lesions. Degenerative skeletal myopathy was present in a large proportion of calves that were born alive and also in a smaller, but substantial, proportion of calves that died at birth. The degenerative skeletal muscle lesions were not typical of the descriptions of classical selenium deficiency, or white muscle disease as it is known in the cattle industry (13–15), as mineralization of the muscle fibers was uncommon and many calves were very young. Others have reported congenital nutritional muscular dystrophy in beef calves from western Canada, but noted that cases were unusual in newborn calves (16). Nevertheless, nutritional deficiencies, particularly selenium or vitamin E, must be considered as a probable cause of these lesions (17,18).
Degenerative skeletal myopathy and necrosis were frequently observed in calves dying of other causes, suggesting that even herds without nutritional myopathy deaths may have deficiency problems. These muscle lesions were commonly seen in calves that died from starvation, exposure, infectious disease, or dystocia. Other problems often linked to selenium deficiency include reproductive disorders, poor growth, and calf health problems (5,19). Free-choice supplementation with selenium does not ensure adequate selenium status in the cows or their offspring (20,21). Given that all but 4 of the study producers reported providing some type of trace mineral supplement to their cows (Waldner, unpublished data), it appears that the management of trace vitamin and mineral supplementation should be re-visited in western Canada.
Like the skeletal muscle lesions, thyroid lesions and cardiac necrosis and degeneration were common histologic findings. These lesions were frequently identified in cases where the etiologic diagnosis was another more commonly recognized cause of death such as starvation, dystocia, or infectious disease. Thyroid lesions were most common in stillborn calves and were least common in calves that were born alive. Histologic lesions in the cardiac muscle were present in all age classes of calves. Unlike skeletal muscle lesions, the risk factors for thyroid and heart lesions, and the effect of mild lesions on calf health and performance, are largely unknown. Others have not found thyroid or heart disease as important causes of death in beef calves (5–7,22). This apparent discrepancy could be explained by the consistent histologic evaluation of all tissues regardless of gross pathological findings in the present study. Further work is needed to determine the importance of these findings.
Inflammatory lesions consistent with infectious disease processes explained fewer deaths than noninfectious diseases in all age categories. It was not surprising that infectious diseases were most commonly identified in calves greater than 3 d of age at death. But even in this age category, only a third of calf losses could be attributed to a disease process characterized by inflammation consistent with infection. The second most commonly affected age category was the neonatal calves.
Only a quarter of abortions were attributed to lesions consistent with an infectious process. Abortions due to well-known infectious causes such as BVDV and IBR were relatively rare in this cohort. Neospora caninum was identified in only 3 calves. The actual frequency of IBR and N. caninum in the submitted fetuses is unknown because testing for these was at the discretion of the pathologist. Nevertheless, identification of these organisms using IHC was considered very unlikely in the absence of lesions suggesting infection. These results were interesting in light of serological evidence that many of these herds had been exposed to these agents (23,24).
Placentitis, or lung lesions attributed to inhalation or hema-togenous spread of agents associated with placentitis, were the most common manifestations of infectious abortions. Even so, the relative importance of placentitis was probably underestimated because only half of the abortion submissions included placenta. Submission rates for placenta were likely low because the placenta is not always delivered with the calf and can be difficult to locate in range managed cattle. Similar logistical constraints, including predation, explain the relatively low submission rates for abortions. If the cases that were submitted differed systematically from those that were not, the study results could be biased (25). However, the submission rate of 35% of aborted fetuses is higher than previously reported (26). Similar bias is likely minimal in the remaining age categories considering > 70% of eligible cases were submitted.
The results of this study differed from previous descriptions of the causes of death in beef calves. There are 3 explanations for these discrepancies. The first is that extensive testing of fixed tissues was undertaken on all cases. Previous reports that evaluated submissions to pathology laboratories in cases of bovine abortion and stillbirth found a diagnosis in 20 to 41% of cases (6–8,27). The current study found that a thorough postmortem examination, including special histochemical techniques, IHC, and the receipt of a detailed history added substantial value, as a diagnosis was made for 64% of abortion and 78% of stillbirth cases.
The significance of some histologic findings and special stains, however, will require further study. For example, histochemical techniques were used to confirm the presence of hemosiderin in the liver. Hemosiderin is an iron-containing pigment that can normally be present in the neonatal period when fetal hemoglobin is being replaced by mature hemoglobin. Hemosiderosis is known to be a genetic condition amongst Salers cattle (28), but there was no evidence of a breed predisposition in the present study. The cause and importance of the severe hemosiderosis seen in some calves from this study are unknown.
In addition to an improved rate of diagnosis, comprehensive laboratory testing likely contributed to different outcomes from previous reports. In a similar, but much smaller, long-term field study, all aborted and stillborn calves were necropsied by local veterinarians; however, histologic examination was performed only on tissues considered abnormal (26). In that study, the most frequently reported causes of abortion were bacterial infection, congenital defects, placental insufficiency, and mycotic infection (26). Similar to the present study, a high proportion of stillbirth losses were attributed to dystocia. The present study’s findings differed from this previous report in that underlying or secondary lesions that may have compromised the calf’s ability to actively participate in the birthing process were identified due to a consistent protocol for tissue submission and histopathologic examination.
Finally, selection bias is a serious limitation for the usefulness of retrospective studies based on records from diagnostic laboratories (25). The extent that selection bias can affect results is illustrated by comparing the present study to a 2002 study of bovine abortion submissions to Prairie Diagnostic Services (9). Bovine submissions to this laboratory are primarily beef-cattle and predominately originate in Saskatchewan, and to a lesser extent Alberta. From the diagnostic results of 338 bovine fetuses, 52% had no diagnosis, 41% were attributed to an infectious disease and 7% to a developmental anomaly. It is not surprising that a retrospective laboratory survey identified more cases with an infectious etiology than this study. Laboratory submissions were likely received from herds experiencing excessive losses while the findings of the present study are less prone to submission bias because producers submitted cases regardless of whether or not the number of losses was unusual.
In previous publications, infectious disease represented 28% to 44% and noninfectious disease 1.1% to 8.6% of all abortion and stillbirth submissions (5–7,9). In this study, summary diagnoses consistent with infectious disease were identified in 33% of the older calves, 20% of the neonates, 2% of the stillborn calves and 18% of the aborted fetuses. While the present study may have done a better job of identifying noninfectious disease, the study might also have underestimated the occurrence of infectious disease. Submission and culture of fresh tissue was not practical due to extensive transport distances and prolonged time from collection to arrival at the laboratory. However, even in studies where culture was routinely used in the laboratory a substantial proportion of cases had inflammatory lesions, suggesting an infectious cause, where no agent was identified (6,7).
Likewise, many calves with developmental anomalies are not routinely submitted to diagnostic laboratories by livestock producers because the affected calves are often rare and the diagnosis is apparent. Three of the 5 reported laboratory studies listed rates of developmental anomalies in abortions or stillbirths ranging between 0.3% to 1.4% (5–7). This study provides an unique indication of the occurrence of developmental anomalies and the nature of these anomalies in beef calves.
Noninfectious disease processes were more common than infectious diseases in all age categories. Many cases had thyroid, cardiac, and skeletal muscle lesions. This study demonstrated the value of routinely submitting a standard set of tissues for diagnostic testing from necropsies. Diagnoses were made in a high proportion of cases, and in some cases contributing factors were identified that can be potentially controlled through improved nutrition and management. Future investigations should consider the effects skeletal muscle, thyroid and heart lesions have on calf health and productivity, and the role of trace minerals and vitamins, including vitamin E and selenium, in calf survival.
Acknowledgments
The data in this paper were collected as part of the field research activities for the Western Canada Study of the Animal Health Effects Associated with Exposure to Emissions from Oil and Natural Gas Field Facilities. Funding support was provided through the Western Interprovincial Scientific Studies Association (WISSA). The authors acknowledge the dedicated technical support of Cindy Jelinski, Diane Sanjenko, and the staff of Prairie Diagnostic Services in managing the large number of samples associated with this study. CVJ
Footnotes
Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (hbroughton@cvma-acmv.org) for additional copies or permission to use this material elsewhere.
References
- 1.Anonymous. National Animal Health Monitoring System (NAHMS), N238.797. Fort Collins, CO: Centers for Epidemiology and Animal Health, USDA:APHIS:VS; 1997. Part II: Reference of 1997 beef cow-calf health and health management practices; pp. 1–44. [Google Scholar]
- 2.Anonymous. Beef Cow/Calf Health and Productivity Audit (CHAPS) Fort Collins, CO: Center for Animal Health Monitoring, USDA:APHIS:VS; 1994. Part III: Beef cow/calf health management; pp. 1–46. [Google Scholar]
- 3.Kaliel DA, Perillat B. Economic, productive and financial performance of Alberta cow/calf operations for the production year 2002. Edmonton, Alberta: Alberta Agriculture, Food and Rural Development; 2004. pp. 1–9. [Google Scholar]
- 4.Mathison GW. The beef industry. In: Martin J, Hudson R, Young B, editors. Animal Production in Canada. Edmonton, Alberta: University of Alberta; 1996. pp. 35–74. [Google Scholar]
- 5.Alves D, McEwen B, Hazlett M, et al. Trends in bovine abortions submitted to the Ontario Ministry of Agriculture, Food and Rural Affairs, 1993–1995. Can Vet J. 1996;37:287–288. [PMC free article] [PubMed] [Google Scholar]
- 6.Khodakaram-Tafti A, Ikede BO. A retrospective study of sporadic bovine abortions, stillbirths, and neonatal abnormalities in Atlantic Canada, from 1990 to 2001. Can Vet J. 2005;46:635–637. [PMC free article] [PubMed] [Google Scholar]
- 7.Kirkbride CA. Etiologic agents detected in a 10-year study of bovine abortions and stillbirths. J Vet Diagn Invest. 1992;4:175–180. doi: 10.1177/104063879200400210. [DOI] [PubMed] [Google Scholar]
- 8.Kirkbride CA, Bicknell EJ, Reed DE, et al. A diagnostic survey of bovine abortion and stillbirth in the northern plains states. J Am Vet Med Assoc. 1972;162:556–560. [PubMed] [Google Scholar]
- 9.Pople N. Diagnosis in bovine abortions. Anim Health. 2003;5:1–2. [Google Scholar]
- 10.Waldner CL. Western Canada study of animal health effects associated with exposure to emissions from oil and natural gas field facilities. Study design and data collection 1: Herd performance records and management. Arch Environ Occup Health. 2008;63:167–186. doi: 10.3200/AEOH.63.4.167-184. [DOI] [PubMed] [Google Scholar]
- 11.Shahriar FM, Clark EG, Janzen E. Coinfection with bovine viral diarrhea virus and mycoplasma bovis in feedlot cattle with chronic pneumonia. Can Vet J. 2002;43:863–868. [PMC free article] [PubMed] [Google Scholar]
- 12.Njaa BJ, Clark EG, Janzen E, et al. Diagnosis of persistent bovine diarrhea virus infection by immunohistochemical staining of formalin-fixed skin biopsy specimens. J Vet Diagn Invest. 2000;12:393–399. doi: 10.1177/104063870001200501. [DOI] [PubMed] [Google Scholar]
- 13.Maxie MG. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. 5th ed. Vol. 1. Toronto, Ontario: Saunders Elsevier; 2007. pp. 236–239. [Google Scholar]
- 14.Radostits OM, Gay CC, Blood DC, et al. Veterinary Medicine, a Textbook of the Diseases of Cattle, Sheep, Pigs, Goats, and Horses. Philadelphia: W.B. Saunders; 2003. [Google Scholar]
- 15.Smith BP. Large Animal Internal Medicine. 3rd ed. St. Louis, Missouri: Mosby; 2002. [Google Scholar]
- 16.Abutarbush SM, Radostits OM. Congenital nutritional muscular dystrophy in a beef calf. Can Vet J. 2003;44:738–739. [PMC free article] [PubMed] [Google Scholar]
- 17.Kennedy S, Rice DA, Davidson WB. Experimental myopathy in vitamin E and selenium depleted calves with and without added dietary polyunsaturated fatty acids as a model for nutritional degenerative myopathy in ruminant cattle. Res Vet Sci. 1987;43:384–394. [PubMed] [Google Scholar]
- 18.Orr JP, Blakley BR. Investigation of the selenium status of aborted calves with cardiac failure and myocardial necrosis. J Vet Diagn Invest. 1997;9:172–179. doi: 10.1177/104063879700900211. [DOI] [PubMed] [Google Scholar]
- 19.Enjalbert F, Lebreton P, Salat O. Effects of copper, zinc and selenium status of performance and health in commercial dairy and beef herds: Retrospective study. J Anim Physiol Anim Nutr. 2006;90:459–466. doi: 10.1111/j.1439-0396.2006.00627.x. [DOI] [PubMed] [Google Scholar]
- 20.Valle G, McDowell LR, Pritchard DL. Selenium status of beef calves from dams receiving selenium supplementation. J Anim Vet Advan. 2003;2:338–342. [Google Scholar]
- 21.Valle G, McDowell LR, Pritchard DL. Effects of supplementing selenium to a beef cattle cow-calf herd on tissue selenium concentration. J Anim Vet Advan. 20032:126–132. [Google Scholar]
- 22.Young JS, Blair JM. Perinatal losses in a beef herd. Aust Vet J. 1974;50:338. doi: 10.1111/j.1751-0813.1974.tb14101.x. [DOI] [PubMed] [Google Scholar]
- 23.Waldner CL, Kennedy RI. Antibodies for bovine viral diarrhea virus and infectious bovine rhinotracheitis virus, and persistent infection with BVDV in beef calves at weaning and health and performance in cow-calf herds. Am J Vet Res. 2008;69:916–927. doi: 10.2460/ajvr.69.7.916. [DOI] [PubMed] [Google Scholar]
- 24.Waldner CL. Serological status for N. caninum, bovine viral diarrhea virus, and infectious bovine rhinotracheitis virus at pregnancy testing and reproductive performance in beef herds. Anim Reprod Sci. 2005;90:219–242. doi: 10.1016/j.anireprosci.2005.03.017. [DOI] [PubMed] [Google Scholar]
- 25.Martin SW, Meek AH, Willeberg P. Veterinary Epidemiology: Principles and Methods. Ames, Iowa: Iowa State Univer Pr; 1987. [Google Scholar]
- 26.Waldner CL. Monitoring beef cattle productivity as a measure of environmental health. Environ Res Sec A. 2001;86:94–106. doi: 10.1006/enrs.2001.4239. [DOI] [PubMed] [Google Scholar]
- 27.Roberts SJ. Veterinary Obstetrics and Genital Diseases (Theriogenology) 2nd ed. Ithaca, New York: Roberts SJ; 1971. [Google Scholar]
- 28.O’Toole D, Kelly EJ, MCallister MM, et al. Hepatic failure and hemochromatosis of Salers and Salers-cross cattle. Vet Pathol. 2001;38:372–389. doi: 10.1354/vp.38-4-372. [DOI] [PubMed] [Google Scholar]