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];
Keywords: horse; melatonin; seasonality; progesterone; light mask; blue light
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 anal