Use of Squeeze-Induced Somnolence for Minor Procedures in Thoroughbred Foals: 22 Cases

Abstract OBJECTIVE To describe clinical, imaging, gross, and histopathological abnormalities associated with osteochondral necrosis of the femoral condyles in foals and identify features suggestive of a common pathogenesis. ANIMALS 8 Thoroughbred foals euthanized with a presumptive diagnosis of necrosis of the femoral condyles. PROCEDURES Postmortem CT was performed on all distal femoral epiphyseal samples. The articular epiphyseal cartilage complex (AECC) of affected distal femurs was examined grossly and histologically, focusing on lesions of interest identified on CT images. RESULTS 7 foals were between 9 and 23 days old at the time of euthanasia; 1 foal was 85 days old. Concurrent illness (neonatal maladjustment syndrome, neonatal isoerythrolysis, or infection such as enteritis and omphalitis) was diagnosed in 7 foals. The characteristic antemortem radiographic and postmortem CT finding was a crescent-shaped osteochondral flap displaced from the affected medial femoral condyle. Synovial fluid cytology from affected joints was either within normal limits or consistent with mild inflammation. Histologically, all lesions were characterized by osteochondral necrosis and detachment of the AECC. In 6 foals, polymorphonuclear cells were found within growth cartilage canals, representing septic cartilage canals. CLINICAL RELEVANCE Osteochondral necrosis was interpreted to be secondary to bacterial colonization of the distal femoral AECC, evidenced by septic cartilage canals identified in 6 of 8 foals. This uncommon condition was previously thought to arise from an ischemic event, but the disease process was not well understood. An improved understanding of the pathogenesis of osteochondral necrosis is the first step in formulating more successful preventative and treatment strategies.

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Preweaned Thoroughbred (Equus caballus) foals exhibit fewer behavioural signs of distress if accompanied by a handler while separated from their dam during covering

BSAP Occasional Publication ◽

10.1017/s0263967x00041343 ◽

2004 ◽

Vol 32 ◽

pp. 161-163

Author(s):

S McGee ◽

H V Smith

Keyword(s):

Equus Caballus ◽

Separation Distress ◽

Thoroughbred Foals

Thoroughbred mares (Equus caballus) are usually first teased 6 days post foaling and during this brief (often 3-6 minutes) process the mare's foal will be left alone in its stable. This will be repeated daily until the mare goes out of season. During this part of her cycle she may later be sent for covering by the resident stallion. On some farms the foal is alone in its stable during covering and this period can last for anything from 20 minutes to an hour, during which the foal typically exhibits signs of considerable distress. Though the foal can be heard whinnying for the mare, it has not previously been noted what behaviours the distressed foal exhibits during this separation. Though a recent study by Houpt (2002) looked at responses of 10 pony mares and their foals to brief weekly periods of separation at up to nine weeks of age, most research on separation distress in foals has previously been done with respect to the artificial weaning process, an event that most Thoroughbred foals experience by 6-7 months of age.

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