62
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
mares were maintained outdoors on a farm within an 8 km radius of the mares in
the other experimental groups and had been living outdoors as a herd for several
years prior to the study. Mares with constant exposure to the natural climatic
challenges of the environment are known to exhibit a tighter breeding season and
enter winter anoestrus, as is characteristic of feral mares [22]. While every effort
was made to control for breed, body condition, age and nutritional intake, the
management history of the animals in the experimental groups probably influenced
their reproductive status in mid-November.
At the end of the study, 4/19 of the control mares were reproductively cycl ing
despite having received no stimulatory light signal. This finding of a subset of mares
that continued to cycle throughout the year is supported by previous studies [23,24]
and is a phenomenon unique to the equine species.
Occasionally during the study incidents with the prototype masks, such as mud
coating the reflective inner cup and masks breaking or falling off, meant that mares
received either a lower intensity of light than intended or no light for a single night.
This could have contributed to an inadequate light intensity failing to stimulate
reproductive activity in the 3 mares from Group 2 that remained anoestrus at the
end of the trial. It is believed that an optimised mask design may increase the success
rate achieved.
Our finding that low-level blue light from mobile light masks can successfully advance
the breeding season in mares has implications for improving efficiency of equine
breeding management. A recent survey of farm managers found that the cost of
maintaining mares indoors under lights was approximately €120/mare/week
(personal communication to B.A. Murphy). This figure was calculated based on
combined feed, bedding, labour and energy costs. Assuming that artificial lighting
programmes are initiated on 1 December and the earliest that a mare is covered is
15 February, the shortest duration a mare will be maintained under lights is until the
first pregnancy check at Day 15 post covering. Thus the minimum duration of light
therapy is 12 weeks (until 1 March). Our results suggest that the equine breeding
season could now be advanced while the mares live outside in groups. This method
is unlikely to reduce feed costs significantly, but bedding, labour and energy costs
would be significantly reduced. In addition to the cost saving benefits, it has been
reported that mares fed on fresh pasture ovulate earlier in the breeding season than
mares fed on dry forage [25].
A previous investigation of the potential of delivering light to the mares eyes using
white light-emitting blinkers as an alternative to stabling clearly showed the potential
of this method [26]. The authors suggested that further technological advances were
required before it became a viable option. The light mask described here represents
the next step in the advancement of this technology towards a viable alternative for
horse breeders, but with an important difference – the use of blue light delivered via
LEDs to a single eye that has been shown to optimally inhibit melatonin levels
necessary to provide the long-day photoperiod that stimulates the mare’s
reproductive axis [19].
Horses are naturally herd animals and the social instinct for bonding with individuals
is an important component of their socioecology [27]. Domestication by man has led
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