Smaller foals, shorter gestation noted after blue-light therapy

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Image: O’Brien, Darcy-Dunne, Murphy/Equine Science Update

Shorter gestation and smaller foals with shorter hair were noted in mares who were treated with blue light in a study involving warmblood mares in Germany.

It has been known for a long time that changing day length influences equine reproduction. The natural breeding season for horses occurs during the brighter months of the year (April in the northern hemisphere), which presents a challenge for breeders who require foals to be born early in the year.

This has led to the search for ways to advance the onset of reproductive activity, including using stable lighting to artificially prolong the daylight to 16 hours from mid-December onwards, to stimulate the onset of oestrus activity.

Professor Christine Aurich and her research team at the University of Veterinary Medicine in Vienna, Austria have been investigating the effect of blue light treatment on gestation length, and pregnancy outcome. Their work has been published in the journal Domestic Animal Endocrinology.

Previous research by one of the study team, Dr Barbara Murphy, head of Equine Science at University College Dublin and founder and CEO of light therapy company Equilume, demonstrated that a similar effect could be produced by shining a low-intensity blue light into one eye.

In the latest research, 20 pregnant Warmblood mares, each carrying a single pregnancy completed the study, which covered two consecutive years. The mares were kept at the Brandenburg State Stud at Neustadt, Germany, and were aged from three to 17. All were bred by AI.

During one pregnancy the mares wore an Equilume Light Mask which directed 50 lux blue LED light (468nm) into one eye from 08.00 to 23.00 daily from mid-December onwards. During the second pregnancy, the same mares received no treatment, and so acted as controls.

The researchers found that pregnancy length was shorter in blue LED light-treated mares than in controls. Foals born to blue LED light-treated mares had lower wither heights, but were of similar weights and took less time to stand after birth than did control foals.

They also noticed differences in hair growth. Foals born to light-treated mares had reduced hair length compared to controls and hair regrowth in treated mares was reduced.

They conclude: “Foaling can be advanced with head-worn masks emitting blue LED light to a single eye without negative effects on foal maturity. Blue LED light resulted in the birth of slightly smaller foals compared to controls. Furthermore, foals born to blue LED light-treated mares had a shorter hair coat than control foals, demonstrating that artificial light directed at the mare does reach its fetus and accelerates fetal maturation.”

The study team also comprised Anne Lutzer, Christina Nagel, and Manuela Wulf from the Graf Lehndorff Institute for Equine Science in Neustadt, Germany; Camille Gautier from Vetmeduni Vienna in Austria; and Jörg Aurich from the School of Agriculture and Food Science, University College Dublin, in Ireland.

Effects of blue monochromatic light directed at one eye of pregnant horse mares on gestation, parturition and foal maturity. A Lutzer, C Nagel, B A Murphy, J Aurich, M Wulf, C Gautier, Christine Aurich. Domest Anim Endocrinol (2022)78:106675. https:doi.org/10.1016/j.domaniend.2021.106675

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