The Role of Insulin in Endocrinopathic Laminitis

Laminitis is a devastating disease of horses that usually arises as a consequence of major systemic disease or endocrine disturbances. Research has been confounded by apparently disparate results and theories on pathogenesis. Models of laminitis have greatly advanced our understanding of the disease, yet have mostly involved perturbations of the gastrointestinal tract or inflammatory models. A major trend in research on laminitis in the past few years has been the increasing interest in endocrine dysfunction resulting in laminitis. A new model of laminitis associated with hyperinsulinemia has recently been discovered and the central role of high insulin in triggering endocrinopathic laminitis highlighted. This review discusses the pathophysiology of insulin resistance and hyperinsulinemia in horses and possible mechanisms of insulin-induced laminitis.     

The Macroscopic Vascular Anatomy of the Equine Ethmoidal Area

The vascular anatomy of the ethmoidal area in six normal horses and two normal ponies was studied using vascularcorrosion casts. The major arterial supply to the ethmoidal area sterns from an intracranial source. The internal and external ethmoidal arteries anastomose on the rostral intracranial surface of the cribriform plate to form the arterial ethmoidal rete which arborizes and passes through the perforations of the cribriform plate to supply the ethmoid labyrinth. A minor arterial supply to the ventral portion of the ethmoid labyrinth sterns from a small caudal nasal branch of the sphenopalatine artery. Multiple parallel venules drain the ethmoid labyrinth rostrally to its apex then join the venous drainage from the surrounding sinuses.     

Pathology of Bovine Laminitis Especially As Regards Vascular Lesions

Macro- and microscopical changes in the hooves of 14 cattle having a clinically established diagnosis of laminitis are described, Deviation of the pedal bone was found in 10 of the animals. In acute laminitis, the microscopical changes in the corium were hyperaemia, oedema, thrombosis and haemorrhages. Degenerative changes were found in the epidermis especially in the vicinity of thromboses of vessels in the corium. In chronic laminitis, arteriolosclerosis and arteriosclerosis were constant findings in the corium. There was also a high frequency of chronic thrombi and chronic granulation tissue. Prominent features in the lamellae epidermales were hyper- and parakeratosis. As judged from changes in arterioles and arteries, hypertension is suggested to be a pathogenetic factor in bovine laminitis.cattle; laminitis; histology; arteriolosclerosis; arteriosclerosis.     

Correlation of Plasma Insulin Concentration with Laminitis Score in a Field Study of Equine Cushing's Disease and Equine Metabolic Syndrome

This study aimed to investigate endocrinologic test values and the response to treatment of two commonly encountered causes of endocrinopathic laminitis, equine Cushing's disease (ECD) and equine metabolic syndrome (EMS), in a veterinary practice setting. In particular, the study aimed to determine whether insulin concentration correlated to the severity of clinical laminitis in horses with EMS or ECD. Twenty-five horses were included in the study and assigned to one of three groups: ECD (n = 6), EMS (n = 10), and controls (n = 9). Blood samples were collected at an initial visit and then at regular intervals for the next 12 months. Plasma concentrations of adrenocorticotropin (ACTH), cortisol, and insulin and serum concentrations of glucose and total thyroxine (T4) were obtained. Horses with ECD had significantly higher plasma ACTH concentrations than EMS horses or controls. Horses with EMS and ECD both had significantly higher plasma insulin concentrations than control horses, which was correlated with the Obel grade of laminitis (r = 0.63). After treatment, there was a trend for a reduction in plasma ACTH concentration in horses with ECD. A program of diet and exercise for horses with EMS resulted in reductions in both plasma insulin concentrations and bodyweight, which was variable, depending on the individual. There was a significant correlation between the change in plasma insulin concentration and Obel grade of laminitis (r = 0.69). This study has highlighted the importance of baseline plasma insulin concentration as a potential indicator of the susceptibility of horses to laminitis and the response to a program of diet and exercise.     

The Role of Thermography in the Management of Equine Lameness

Equine thermography has increased in popularity recently because of improvements in thermal cameras and advances in image-processing software. The basic principle of thermography involves the transformation of surface heat from an object into a pictorial representation. The colour gradients generated reflect differences in the emitted heat. Variations from normal can be used to detect lameness or regions of inflammation in horses. Units can be so sensitive that flexor tendon injuries can be detected before the horse develops clinical lameness. Thermography has been used to evaluate several different clinical syndromes not only in the diagnosis of inflammation but also to monitor the progression of healing. Thermography has important applications in research for the detection of illegal performance-enhancing procedures at athletic events.