46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
59
This provided uniform, diffuse light and minimised distraction to the horse,
permitting maintenance of normal behaviour. A 3 cm diameter hole was cut through
the cup 1 cm below the LED to permit peripheral vision on the right side.
The LED used was a Kingbright 7.6 °— 7.6 mm Super Flux LED Lamp L-7676CQBCD Blued. It has a luminous intensity of 1300 millicandelas when powered by a current
of 70 mA. The peak wavelength was 468 nm, which is within the desired range for
optimum suppression of melatonin in mammals. The spectral line half width was 25
nm, providing a broad margin for error in terms of the efficacy of the wavelength.
The beam angle of the LED was 70° allowing for some degree of movement between
the LED and the horse’s eye. Each mask was individually calibrated using different
levels of resistance to provide 50 Lux of diffuse light to the horse’s eye. The Lux
levels (illuminances) for each individual mask were adjusted and measured using a
Lux meter (LX-1010 B Digital Lux Meter).
Each mask used 4 Duracell Pro-cell AA sized 1.5 V batteries (replaced at 2-week
interval) and powered a circuit containing an Arduinoe board, a switch (on/off), a
clock and a set of resistors. The Arduino board was programmed to turn the LED
on at 16.30 h each day and switch it off at 23.00 h every night. A resistor was
connected in series with the LED to determine the current flowthat produced
illuminance of 50 Lux. In order to save power and prolong the battery lifetime, much
of the Arduino functionality was put in a sleep mode. The circuit also included a real
time clock module that kept time so that the Arduino could power the LED for
specific intervals. The real time clock had its own small, independent battery so that
it did not lose time when the switch for the main circuit was turned off.
Experimental protocol
Beginning on 1 December, Group 1 received light therapy via artificial lighting indoors
in individual stalls. The lights, which provided 250 Lux of light to each mare at eye
level, were switched on at 16.30 h every day and remained on until 23.00 h each
night. Also beginning on 1 December, Group 2 received individual light therapy from
head worn masks that provided 50 Lux of blue light to the right eye of each mare.
The mask light turned on automatically at 16.30 h each day and turned off at 23.00 h
every night. Group 3 served as a control group and received no artificial light therapy,
but was exposed to the natural environmental light/dark cycles for the duration of
the experiment.
Beginning on 20 November and continuing at 2-week intervals throughout the
experiment the mares underwent transrectal ultrasound examination and jugular
venipuncture. Ovarian activity in terms of follicle number and size, presence or
absence of corpora lutea, cervical tone and presence or absence of uterine oedema
were recorded for each mare at every ultrasound examination and the blood
samples were assayed to establish circulating progesterone concentrations. Oestrous
cyclicity was defined as the presence of follicles >20 mm and the confirmation of an
ovulation determined by the presence of a previously unrecorded corpus luteum or
corpus haemorrhagica on an ovary in conjunction with progesterone levels >1 ng/ml.
Transitional phase was defined as follicles >20 mm and associated physiological
characteristics typical of oestrous activity but in the absence of progesterone levels
indicative of ovulation.
59