Veterinary Services

Two cases of bracken poisoning were diagnosed postmortem at Dumfries. One case was an extensively reared suckler cow that had been ill for one week, eventually becoming recumbent. The second case involved a two-month-old Limousin cross heifer calf, one of two sudden deaths in three days. Haemorrhages were evident throughout the carcase (Fig 1) and the left lung was dark red and turgid and distended with blood. A large thrombus was noted at the junction of the main stem, bronchi and trachea. Possible causes of haemorrhage, including bracken poisoning, acute septicaemia, caudal vena cava thrombosis and acute bovine viral diarrhoea (BVD) virus infection were considered.  No significant bacteria or viruses were isolated from the case and the gross pathology was considered inconsistent with caudal vena cava thrombosis. A reduction in the number of myeloid cells was noted in the bone marrow, consistent with a diagnosis of bracken poisoning. Direct ingestion of the toxin by the calf, or through the milk were considered possibilities; however, no evidence of poisoning was detected in the cows.

Generalised and systemic conditions

At Ayr, postmortem examination of a yearling dairy-bred bullock that died suddenly confirmed a diagnosis of clostridial enterotoxaemia. Three animals at grass had died in a week. The small and large intestines were distended with brown, watery fluid and epsilon and alpha toxins were detected in the small intestinal contents.

A seven-month-old Simmental cross heifer was submitted to Inverness from a herd in Ross-shire following an acute illness.  The heifer was injected with florfenicol but died within an hour. Six calves had died on the unit earlier in the year due to pneumonia. Petechial, epicardial haemorrhages and pleural ecchymotic haemorrhages were evident at postmortem examination. The lungs were grossly normal apart from a small area of consolidation at the caudal tip of one of the diaphragmatic lobes, which was 3 cm in diameter. The small intestinal contents were bloody and the large intestinal contents were watery, foul smelling and contained shreds of mucosa.

Pasteurella trehalosi was isolated from the liver, and histopathology revealed widespread neutrophil infiltration of hepatic sinusoids and large numbers of neutrophils in pooled blood within the central veins and portal vasculature. These findings of an acute hepatitis supported a diagnosis of systemic pasteurellosis.

There was also evidence of a chronic active enteritis. The animal proved seronegative for BVD virus. Systemic pasteurellosis is common in sheep but unusual in cattle.

Alimentary tract disorders

In Ayrshire, two adult dairy cows were submitted for postmortem examination from the same farm on successive days. The first case had died as a result of a distal ileal obstruction. The obstruction consisted of small black stones and a mesh of fibrous material comprising the stemmier parts of conserved forage.The second case had died from haemorrhage into the alimentary tract from an abomasal ulcer.

The herd had undergone a number of dietary changes following a reduction in milk yield after housing, and this may have been linked to the digestive tract conditions diagnosed.

Respiratory tract conditions

Infectious bovine rhinotracheitis (IBR) was commonly diagnosed as a cause of respiratory distress in November. In Aberdeenshire, IBR virus was isolated from nasal swabs submitted from a group of pyrexic nine-month-old cattle with respiratory disease, and IBR virus antigen was detected by the fluorescent antibody test (FAT) of a pluck submitted from an animal that had died on the same unit. The cattle had been purchased from an IBR-free herd in Dumfries, and had been recently weaned and transported to Northern Aberdeenshire.

In Perthshire, a six-month-old Aberdeen Angus calf, which had been unwell for four weeks, was submitted for postmortem examination. Other calves in the group had shown intermittent signs of respiratory tract disease, with some response to antibiotic therapy. Examinations revealed well established, deep, necrotic lesions approximately 6 x 3 cm on either side of the tongue, with an area of deep necrosis within the soft tissues of the left pharyngeal/laryngeal region. The apical right lung was consolidated and contained a necrotic abscess approximately 4 cm in diameter. Focal necrotic lesions were present at intervals along the small intestine. Inflammation penetrated the wall of the intestine in several places to establish localised peritonitis. Petechial haemorrhages were present throughout a number of organs and the blood had a thin/watery appearance. No respiratory viruses were detected by the FAT.  Mannheimia haemolytica was isolated from the lung, throat and tongue lesions.  Histology indicated necrotising glossitis, acute necrotising fibrinous bronchopneumonia and peritonitis.

An outbreak of respiratory disease involving 90 three- to four-month-old purchased calves bucket reared on milk was investigated by Dumfries.  Nine calves in the group were severely affected and the entire group was reported to be coughing.  Gross lesions typical of respiratory syncytial virus (RSV) infection were noted in the diaphragmatic lobes of the lung and severe lung consolidation and abscessation was noted in the apical lobe. RSV was not detected by the FAT, and bacterial cultures from the lung proved sterile due to antibiotic treatment; however, histopathological lesions consistent with RSV infection were noted, with apical lobe changes consistent with bacterial and mycoplasma infection. The changes suggested a previous bacterial-type pneumonia with terminal RSV infection.

A spring-born suckled calf from a different group on the same farm was subsequently submitted for postmortem examination, one of two in the group to have died. A diagnosis of viral pneumonia was made on the basis of gross pathology, and RSV infection was confirmed by the FAT and histopathology.

Reproductive tract disorders

Samples of vaginal mucus were submitted to St Boswells from 18 cows in a large suckler herd suffering from poor fertility.  Campylobacter fetus fetus was isolated from five of the animals.

Musculoskeletal conditions

In Ayrshire, 25 July- and August-born suckled calves were disbudded and/or dehorned, then returned to grass. The dehorning procedure consisted of running the calves from a concrete-floored pen, through a crush for the administration of local anaesthetic. The calves were run through the crush for a second time to be dehorned. The next day, four calves were lame on their hindlegs and one animal had pus exuding from the lateral coronet.

An entire bull aged 14 months, dehorned in the same crush using the same procedure, was subsequently submitted for postmortem examination after developing lameness on all four feet. It had become progressively worse until pus appeared at the coronet of the rear lateral right digit. At postmortem examination subcutaneous oedema was present affecting the region from above the coronets of the hindlegs to the hocks. The digits were examined externally and the hooves exungulated for internal examination.  Extensive lesions were present in the hindfeet, with less severe lesions in the forefeet.  Histopathology was suggestive of laminitis and bacteraemia. The laminitis may have been induced by local trauma following restraint in the crush. It was concluded that lameness had resulted from trauma to the feet, causing a loss of integrity of the hoof capsule and severe sepsis in the hindfeet, and laminitic-type damage to the coria of the feet. The crush was reported to be in a good state of repair, with an embossed aluminium checkerboard plate floor. It had been used previously for the same procedures without ill effect. A bar had not been placed behind the calves when they were handled, and it is possible that their pulling back against the head yoke resulted in excessive trauma to the feet on an abrasive crush floor.