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to horses being housed in individual stalls, fed high-energy concentrate feeds with
heavy interference in natural breeding behaviours. Studies have shown that a lack of
social interaction, a high-concentrate, low-forage diet and reduced locomotor
activity can result in the development of stereotypic behaviour [28–31]. The
development of management techniques that allow horses to be maintained
outdoors, in social groups with access to grazing could reduce negative behaviours
and risk of illness and therefore improve animal welfare. This study reports that
advancement of the breeding season using low-level light stimulation to one eye
results in early shedding of the winter coat similar to what is seen in mares
maintained under stable lighting. While a control group unexposed to artificial light
was not examined for shedding in this study, it is commonly accepted that shedding
of the heavier winter coat does not occur until much later in the season [32]. The
relationship between photoperiod and seasonal changes in the equine pelage has
previously been reported [33]. For many competitive equestrian disciplines such as
showing and showjumping, the development of a smooth coat in summer is a sought
after and a valuable characteristic of the natural equine breeding season. The ability
to advance the onset of shedding using light therapy is a management technique
already utilised by some sport horse trainers; however, the associated cost of
housing could be considered prohibitive by many more.
The ability to provide light therapy in a cost effective manner while the horses
remain outdoors offers a novel method of achieving desired winter coat loss earlier
in the year.
In conclusion, this study has shown that timed low-level blue light to one eye
provided by a head worn mask is as effective as indoor barn lighting at advancing the
equine breeding season, but with economic benefits for the breeder and welfare
benefits for the horse.
Authors’ declaration of interests
A priority preliminary patent application was filed in Ireland in May 2011 (Patent #
S2011/0245) by University College Dublin entitled ‘An apparatus and method for
inhibiting melatonin synthesis in a horse’ which describes an invention similar to the
light mask used in the current study.
Ethical animal research
All experimental procedures were approved by the University College Dublin
Animal Research Ethics Committee and the University of Kentucky Institutional
Animal Care and Use Committee protocol number 2012-0928.
Sources of funding
This study was partly funded by an Enterprise Ireland Commercial Case Feasibility
Support Grant to B.A. Murphy.
Acknowledgements
We would like to gratefully acknowledge the staff and management of Maine Chance
Farm and Castleton Lyons Farm in Lexington, Kentucky, for help in conducting this
study.
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