56
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
Blue light from individual light masks
directed at a single eye advances the
breeding season in mares
B. A. MURPHY*, C. M. WALSH, E. M. WOODWARD†, R. L. PRENDERGAST‡, J. P. RYLE‡, L.
H. FALLON§ and M. H. T. TROEDSSON†
School of Agriculture and Food Science, University College Dublin, Ireland
†The Maxwell H. Gluck Equine Research Center, University of Kentucky, USA
‡School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Ireland
§Hagyard Equine Medical Institute, Kentucky, USA.
*Correspondence email: [email protected];
Summary
Reasons for performing study: Artificial lighting is commonly used to advance
the breeding season in horses. Light masks have been developed that direct light at a
single eye to inhibit the production of melatonin, the decoder of photoperiod for
seasonally breeding animals.
Objectives: To investigate whether low-intensity blue light from light masks was
effective at advancing the breeding season in mares.
Study design: Controlled experiment.
Methods: Data on reproductive activity was collected from 3 groups of mares
maintained on Kentucky horse farms under various lighting conditions between 20
November 2011 and 10 February 2012: 59 nonpregnant, healthy Thoroughbred
mares were used. On 1 December 2011, Group 1 (n = 16) was housed indoors
under barn lighting (250 Lux) until 23.00 h daily. Group 2 (n = 25) wore light masks
programmed to turn on from 16.30 h until 23.00 h daily and was maintained
outdoors. Group 3 (n = 19) was maintained outdoors under the natural photoperiod
as control. At 2-week intervals, rectal ultrasound examinations were performed and
blood was collected for progesterone analysis. Oestrous cyclicity was defined as the
presence of follicles >20 mm diameter detected in conjunction with serum
progesterone >1 ng/ml and confirmation of ovulation by transrectal ultrasound
examination.
Results: On 10 February, the number of mares exhibiting oestrous cyclicity was
14/16 (87.5%) in Group 1; 20/25 (80%) in Group 2; and 4/19 (21%), in Group 3.
Pairwise comparison of groups revealed no difference in the number of cycling mares
between Groups 1 and 2 (χ2 test, P = 0.3348) whereas differenceswere observed
between Groups 1 and 3 (χ2 test, P<0.0001) and Groups 2 and 3 (χ2 test, P<0.0003).
Conclusions: Low-intensity blue light to a single eye froma light mask is an
effective alternative to maintenance of mares indoors under lights for advancing the
breeding season. Mobile light therapy for horses could have economic benefits for
the breeder by reducing the costs of maintaining mares indoors, and welfare benefits
for horses by permitting outdoor maintenance.
Keywords: horse; melatonin; seasonality; progesterone; light mask; blue light
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