At the craniolateral extent of the bony swelling there was sudden disruption to the broad hyper- echoic line representing bone surface which, by itswidth of.
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in all affected elbow joints was clearly visible on the radiographs (Fig 2). Lateromedial radiographs were taken of the affected elbow joints but provided little additional information to that gained from the dorsolateral, palmeromedial oblique view. Ultrasonographic examination of normal elbow joints in the present study using a 7-5 MHz linear transducer with stand-off pad (MacRae and Scott 1999) failed to identify the joint pouch and lateral ligament. Detailed ultrasonographic examination of the lateral aspect of affected elbow joints proved difficult because of the strictly limited skin contact area, despite using a stand-off pad, resulting from the irregular convex joint surface. Ultrasonographic examination of the lateral aspect of affected elbow joints did not show increased joint fluid. At the craniolateral extent of the bony swelling there was sudden disruption to the broad hyperechoic line representing bone surface which, by its width of 10 to 20 mm and absence of fluid, did not represent the elbow joint. These margins of the hyperechoic line observed during ultrasonographic examination corresponded to the enthesophytic reaction noted during radiographic examination (Fig 2). Ultrasound examination of the caudolateral aspect of the elbow joint revealed an irregular but continuous hyperechoic line in many affected joints. Gross postmortem examination of affected elbow joints revealed severe erosion of articular cartilage and extensive osteophyte formation. Enthesophyte formation was best demonstrated by boiled-out preparations (Fig 3). In the present study the majority of sheep affected with elbow arthritis were rams, which comprise less than 5 per cent of the adult sheep population in the UK. This apparent predisposition of the male sex may be considerably influenced by economic factors; rams cost approximately 10 to 20 times more than female flock replacements and are, therefore, more likely to be subjected to veterinary examination. Rapid growth and excessive body condition in ram lambs and shearlings, demanded for sale purposes, may predispose the elbow ligament to damage but studies using larger populations are needed before firm conclusions can be reached. In general practice, diagnosis of osteophyte formation and enthesophyte reaction involving the lateral ligament of the elbow joint is based upon a history of chronic forelimb lameness, bony swelling on the lateral aspect of the joint with greatly reduced joint excursion, normal prescapular lymph node(s) and the absence of other joint or foot lesions. The palpable bony reaction can be precisely measured with McLintock calipers and compared to a similar class of stock on the farm. There is no effective treatment for this painful condition. Sheep with elbow arthritis should be euthanased for welfare reasons and must not be transported to markets. Regular hoof care programmes operated as part of the veterinary controlled flock health plan will reduce the prevalence of many causes of lameness, including footrot. This will ensure that other more insidious causes, such as elbow arthritis, are noticed and promptly presented for veterinary examination thereby preventing further suffering.
References BOERO, M. J., KNELLER, S. K., BAKER, G. J., METCALF, M. R. & TWARDOCK, A. R. (1988) Clinical, radiographic, and scintigraphic findings associated with enthesis of the lateral collateral ligaments of the tarsocrural joint in standard racehorses. Equine Veterinary Journal 6 (Suppl), 53-59 HINDSON, J. C. & WINTER, A. C. (1996) Outline of Clinical Diagnosis of Sheep. Oxford, Blackwell Science. p 131 MACRAE, A. I. & SCOTT, P. R. (1999) The normal ultrasonographic appearance of ovine joints and the uses of arthrosonography in the evaluation of chronic ovine joint disease. Veterinary Journal 158, 135-143 SCOTT, P. R. (1988) Digital amputation as a treatment of septic pedal arthritis in sheep: a study of field cases. Veterinary Record 122, 115-117 SCOTT, C. A., GIBBS, H. A. & THOMPSON, H. (1996) Osteochondrosis as a cause of lameness in purebred Suffolk lambs. Veterinary Record 139, 165-167
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Plasma glucocorticoid levels after pentobarbitone and thiopentone anaesthesia in New Zealand white rabbits A. GONZALEZ GiL, J. C. ILLERA, G. SILVAN, M. ILLERA BARBITURATES have been used as anaesthetics since the 1930s. Despite the development of new anaesthetics, pentobarbitone and thiopentone, among others, are still widely used. In order to assess the response of the adrenal cortex to these anaesthetics in rabbits, data were collected on the heart rate, respiratory rate and glucocorticoid levels of 30 New Zealand white rabbits. The rabbits were maintained under conventional conditions, that is, 12 hours of light and 12 hours of darkness, at 20 to 22°C, with a relative humidity of 50 to 55 per cent and 10 to 15 air renovations per hour. To minimise stress, the rabbits were handled daily for one week before the experiment began. They were then assigned to three treatment groups, each containing 10 animals, and each group was given one of the following solutions intravenously: 30 mg/kg pentobarbitone (Pentobarbital; Braun Medical SA), 20 mg/kg thiopentone (Tiobarbital; Braun Medical SA) or saline solution, as a control. The doses were based upon preliminary experiments and a review of previous anaesthetic studies utilising laboratory rabbits (Flecknell 1987). The solutions were administered via the lateral ear vein. Blood samples were obtained from the lateral ear vein using 21 G needles, at six time points: before the injection, and at 10, 30, 60 and 120 minutes and 24 hours after administration of the anaesthetics or saline. Plasma corticosterone and cortisol levels were measured in each blood sample by a competitive enzyme immunoassay previously validated for this species by Illera and others (1993) (low detection limits were 0 01 ng/ml for cortisol and 0-15 ng/ml for corticosterone). The depth of anaesthesia was monitored by the pedal withdrawal, ear pinch, palpebral, corneal and righting reflexes. When assessing these reflexes, any movement was considered a positive response. Heart rates were calculated from the tracings of an electrocardiogram and respiratory rates were recorded by visually counting respirations. Data collected on glucocorticoid levels, and heart and respiratory rates were subjected to a one-way analysis of variance to compare the effects of treatment at each time point, followed by Fisher's protected least significant difference test when appropriate. The Student's t test was used to compare the time taken for the reflexes to return in the thiopentone and pentobarbitone groups. Differences were considered significant when Veterinary Record (200 1) P
