Determination of minimum light treatment required for photostimulation of winter anoestrous mares.

This research aimed to determine the minimum requirements in terms of light treatment duration and intensity required to stimulate ovarian activity in winter anoestrous mares (horses in a non-breeding phase). The study found that a 35-day photoperiod with less intense light was enough to advance the onset of the breeding season.

Research Objectives

• The primary goal of this research was to establish the minimum number of days and intensity required for photostimulation, which is a light treatment used to stimulate the breeding cycle of mares going through winter anoestrus (a non-breeding phase).
• The researchers aimed to redefine the traditional photostimulation method which uses 14.5-16.0 hours of white light (100 lux), starting near the time of the winter solstice and ending around the summer solstice.
• The study sought to identify if a lesser duration and intensity of light could be used while achieving the same results, thereby making the process more efficient.

Key Findings and Experiments

• In Experiment 1, the researchers discovered that a 35-day exposure to a modified photoperiod (14.5 hours light: 9.5 hours dark, 100 lux), starting at the winter solstice, successfully advanced the onset of the breeding season in Pony mares undergoing winter anoestrus. This is less than the traditional 70 days treatment.
• In Experiment 2, they found that a low light intensity of only 3 lux effectively stopped the increase in melatonin concentrations in the evening, suggesting that lower light levels could effectively manipulate the horses’ biological schedules.
• In Experiment 3, the researchers found that reducing the light intensity further to 10 lux, produced using a 25W white incandescent bulb, was still sufficient for photostimulation of the mares.
• Experiment 4 and 5 revealed that just one hour of light (10 lux) during the photosensitive phase for 35 days could advance the onset of the breeding season in about half of the treated mares, although the effectiveness was lower than in the other experiments.

Significance of the Research

• This research may support efforts to efficiently manage the breeding cycle of mares in the horse industry. By identifying minimum light treatment time and intensity required for photostimulation, less resources may be needed, potentially leading to cost and energy savings.
• By examining the effects of lower light intensities and shorter photoperiods on the onset of mare breeding cycles, this research could help inform future experiments and practices aimed at optimizing the breeding process in mares.