# Influence of Extended Photoperiod Using Blue Light Masks on Hypertrichosis, Coat Condition and General Health Parameters in Horses with Pituitary Pars Intermedia Dysfunction

## TL;DR

This study found that blue light masks may help manage symptoms of a horse hormone disorder by improving coat condition and energy levels.

## Contribution

The study introduces blue light masks as a potential complementary treatment for managing PPID in horses.

## Key findings

- Blue light masks did not change hair length compared to natural light but improved shedding timing.
- Owners reported better coat condition and increased energy in horses wearing blue light masks.
- Blue light treatment showed improvements in PPID symptoms and quality of life.

## Abstract

This study involved 52 owner-recruited horses over 15 years old with pituitary pars intermedia dysfunction (PPID), a condition causing excessive hair growth. The horses were divided into two groups. One group (29 horses) wore blue light masks from mid-December to extend their daylight exposure to 15 h daily. The other group (23 horses) acted as a control and experienced the natural changes in the light/dark cycle. As most (44/52) of these horses received daily medication to treat PPID, a second control group of unmedicated research horses (17 horses) was also recruited and experienced natural daylength changes for 13 months. Researchers measured hair length, hair shedding, and body condition monthly and collected owner feedback about other symptoms every two months. There was no difference in hair lengths between the blue-light-treated and the first control group, but the second control group had shorter hairs. Shedding started a month earlier in the spring for the blue light group. Owners reported better coat condition in April, less fat coverage in April and June, and more energy in February for the blue light group. A final survey showed improved coat condition, fewer PPID symptoms, and better quality of life in the blue light group only. These findings suggest that blue light masks can help manage PPID symptoms and warrant more research.

Fifty-two horses aged >15 years, diagnosed with pituitary pars intermedia dysfunction (PPID), and displaying hypertrichosis were recruited via an online survey of PPID horse owners. From mid-December, group T (n = 29) wore Equilume® light masks extending photoperiod to 15 h daily, while group C1 (n = 23) remained under natural photoperiod. As 85% (44/52) of recruited study horses received pergolide medication, a second unmedicated PPID research herd (C2; n = 17) was recruited and remained under natural photoperiod. Hair coat samples, shedding and body condition scores were collected monthly by owners for 13 months and analysed by the research team. Data related to management, coat condition and PPID clinical signs were collected using bimonthly questionnaires (BMQ). Time (p < 0.001), group (p = 0.025) and time-by-group interaction (p = 0.005) affected hair length. Group differences were attributable to shorter hair lengths in C2, and no differences in hair length occurred between T and C1 (p > 0.05). Time affected shedding scores (p < 0.001) which was advanced by one month in T (p < 0.05). In group T, BMQ responses showed improved coat condition in April (p = 0.035), decreased fat coverage in April and June (p < 0.05), and increased energy/alertness in February (p = 0.022). Improvements in coat condition (p = 0.043), clinical signs of PPID (p = 0.018), and general quality of life (p = 0.035) were reported in T only in a final study questionnaire. Blue light treatment merits further investigation as a complementary treatment for PPID.