Since 2008, a high prevalence of front limb acquired flexural deformities was observed in a Lusitano stud farm. This work aims to evaluate this problem by reporting the results from tissue alterations in the affected animals as well as environmental conditions and management changes that could have led to this observation.
A total of eleven affected animals were studied. In these, complete physical and orthopaedic examinations were performed, specifically the determination of the angle between the dorsal hoof wall and the floor. Radiographic examination, CT imaging, determination of the thickness of the cortical bone of the third metacarpian and histopathology of some tissues collected in biopsy and necropsy were done in a subset of affected foals. All the animals had been supplemented with balanced commercial diet for equine. To investigate a possible genetic cause, two foals from distinct bloodlines were brought to the stud. These also developed the deformities after 6 months. Two of the affected foals were placed in a pasture away from the initial one and two others were admitted at the Faculdade de Medicina Veterinária de Lisboa. In those animals, except for one that had to be euthanized for humane reasons, an improvement was observed on their condition, with partial recovery from the deformity.
Histopathology was performed from (i) the tendon obtained by surgical desmotomy in one foal, (ii) tendon biopsies from three foals and (iii) the tissue of one foal during necropsy. Histologically the most significant alterations were the dissociation of myofibrils of the smooth muscle. This was predominantly seen in the small intestine but also in the walls of small capillary vessels, including those of the tendon vasculature.
The flexural deformities have a complex and multifactorial etiopathogeny. They occur due to uncoupling of the longitudinal development of the bone and its adjacent soft tissues, but also from shortening of the tendon-muscle unit in response to pain. In the case series presented here, there was no obvious cause for the development of this problem, therefore we hypothesised that unusual environmental conditions might have played an important role in the development of this condition, especially those introduced in recent years.
From the stud farm’s establishment in 2000 to 2008, these symptoms had not been observed in any horse, and there was no alteration of diet (quality and quantity), conditions of housing, and physical exercise that the horses experienced.
The appearance of the deformities coincided with the installation of 2-MW wind turbines on land contiguous to the farm, this being the only environmental alteration that has occurred.
[This is the 18-MW Alto da Folgorosa facility of nine Repower MM92 turbines (rotor diameter 303 ft, total height 414 ft). Four turbines began operation in November 2006, the closest one of which (322m from the home) was shut down and removed after the family began legal proceedings, and six additional turbines began operation in September 2008.]
The entire area in which the horses are housed and exercised is ~350-800m [1150-2625 ft] from the nearest wind turbine.
A main objective of the study is characterization of mechanical vibrations induced in different locations of the farm by operation of wind turbines in close proximity, in order to analyse possible effects of such vibrations on horses.
Dissertação de Mestrado em Medicina Veterinária, 2012
Teresa Margarida Pereira Costa e Curto
Faculdade de Medicina Veterinária
Universidade Técnica de Lisboa
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