Research

Research presented at the Equine Symposium of the British Society for Animal Science’s Conference, showed that pregnant mares wearing blue light masks in the final 100 days of gestation had shorter pregnancies, earlier post-foaling ovulations, developed larger follicles, and produced foals that were more mature at birth. The exciting studies, conducted by researchers at the University of Veterinary Medicine in Vienna, Austria, also found that foals from mares wearing light masks in the final months of pregnancy were 15 minutes faster at getting to their feet after birth than foals born to mares that did not receive additional light.

The two-year study was conducted at the historic Brandenburg State Stud in Germany. The blue-light stimulated mares developed larger follicles in the late stages of gestation and could be bred sooner after foaling. Foals born from mares wearing blue light masks also had shorter hair coats, demonstrating that the light perceived by the pregnant mare is transmitted to the foal and influences their physical development in utero.

These study findings show how correct light management of our pregnant mares can improve breeding efficiencies similar to Nature, but still allow foaling earlier in the year to fit with industry timelines.

Stallions too need adequate light duration for optimum fertility. While they can breed all year long, fertility is highest during the longest days of the year. Published studies have shown that semen volume, sperm concentration, libido and reproductive behaviour are all positively influenced by the duration of light. It is recommended that long-day light therapy for stallions also be initiated 70 days prior to the time of peak reproductive activity. This is especially important for young stallions facing their first breeding season when testes size naturally limits the amount of sperm that can be produced.

Research conducted by Equilume’s R&D team in conjunction with University College Dublin has revealed that time of year influences the response to extended daily light on coat growth in horses and ponies. The important practical take away findings from this research (O’Brien et al., 2020) can be summarised as follows:

• Horses and ponies have a strong seasonal rhythm and there are only certain times of the year when they are responsive to extended daylight
• Don’t leave it too late to start light therapy if you want to maintain a summer coat!
• For horses, ensure that lighting starts within one month after the summer solstice
• For ponies, it is advised to start light therapy at the summer solstice
• To induce early shedding of a winter coat, it is recommended that light therapy is initiated on or before the winter solstice
• The environmental temperature affects a horse or pony’s response to light therapy – ensure they are protected from the elements and well-blanketed
• Nutrition is very important and should be carefully monitored so that increased energy is provided to compensate for temperature drops
• Horses and ponies respond differently and may require different management depending on the rusticity of the breed

Blue light therapy can be used in horses to alter the natural photoperiod and inhibit winter hair coat growth. Seasonal increases in ACTH occur in the fall season but are exaggerated in horses with pituitary pars intermedia dysfunction (PPID). Additionally, PPID horses frequently present with hypertrichosis. Blue light therapy was proposed as a potential management tool for hypertrichosis and for investigating the impact of photoperiod manipulation on ACTH. The PPID horses receiving blue light therapy had lighter hair weights compared to the PPID control horses. These results suggest that blue light therapy does not alter ACTH concentrations but could potentially be used as an additional management tool for hypertrichosis in PPID horses. Manipulation of the photoperiod using blue light therapy did not affect seasonal changes in ACTH in this study.

All mammals have an internal timing system that is responsible for regulating most aspects of physiology and behaviour. This internal timing system, or body clock, is regulated by the daily 24 h rhythms in light and dark exposure and functions in almost every tissue and organ. Domesticated species such as horses are often stabled and exposed to lighting at different times than they would in nature. The cells in hair follicles possess a clock that can be evaluated without the need for more invasive tissue collection. This study aimed to evaluate the clock in hair follicles of horses kept under two lighting systems. After 20 weeks housed with either an incandescent light bulb or a custom-designed LED lighting system, 24 h clock gene rhythms from hair follicles of horses housed under the LED lighting system were found to be stronger. The LED lighting system contained blue light by day, which is more like the light produced by the sun and is known to be responsible for keeping the biological clock ticking, and dim red light at night to help avoid the disruption caused by turning on a white light in the stables at night. Therefore, our results suggest that there is the potential to improve stable lighting for horses to optimise the function of the body clock and ultimately the health of horses. By improving the circadian (24 h) rhythm of horses, all aspects of their physiology can work in better harmony and in synchrony with the environment.