The effects of night light and bedding depth on equine sleep duration and memory consolidation

03 Nov 2020

Fledgling Byte

The effects of night light and bedding depth on equine sleep duration and memory consolidation

By Paul Smith

Take-home message: Changes in bedding depth and exposure to an increased level of night light altered the sleeping behaviour of stable horses.

The welfare and performance of domesticated horses is thought to be influenced by the sleeping pattern of the species. However our understanding of the nominal equine sleeping behaviour, and factors which may influence it, is limited. Similar to humans, horses undergo periods of light and deep sleep which can be determined using detailed analysis of eye movement. Of recent, behavioural assessments of equine sleeping posterior (standing and both sternal and lateral lying) have been accepted as indicators of the different stages of sleep (deep and light). This study aimed to investigate the effect of bedding depth and night light exposure on the sleeping pattern of horses and their ability to perform in a memory based behavioural assessment.

This study evaluated the impact of two straw bedding depths (15 vs. 5cm) and two different levels of night light exposure (high 180lux vs. low 2lux) on the sleeping pattern of ten school horses (4 mares, 6 geldings) of various breeds. In addition, the performance of horses in a memory based spatial awareness test whilst sleeping on the shallow bedding with high light exposure (5cm, 180lux) and deep bedding with low light exposure (15cm, 2lux) was assessed.

Horses were split into two groups of five with sleeping pattern of all horses recorded 24/7. Over the course of the experiment, each group was exposed to the four different sleeping conditions for a week long period. Horses were deemed to be in a deep sleep when either lying laterally (on their side) or resting in a sternal position with their muzzle touching the ground. A light sleep was recorded when horses were observed lying in a sternal position, but with no contact between their muzzle and the ground, or observed in an immobile stance with their head and neck lowered. The effect of sleeping conditions on the memory of horses was conducted in an indoor arena. Food was positioned in bucket in the same corner of the arena, however both visual clues to the position of the food and the entrance point for horses into the arena, altered throughout the test.

In this study, an increased proportion of light standing up sleep and reduced amount of deep lateral sleep was observed when horses slept on the shallow straw bedding depth (5cm). In addition, exposure to a light at night reduced the amount of time spent sleeping in a deep sternal position. Interestingly, horse performance in the food based memory tests was not majorly impacted by sleeping conditions.

Findings from this study indicate an inappropriate depth of straw bedding can have an effect on equine sleeping patterns and potentially horse comfort.  Subsequently this is the first study to highlight the impact of night light exposure on the sleeping pattern of horses. Furthermore, this work has the potential to open a new chapter in horse welfare and husbandry by highlighting the impacts bedding depth and night light exposure can have on equine sleep.

This study was conducted by Daniela Amiouny (Aberystwyth University), Runner up in this year’s BSAS Undergraduate Thesis of the Year Award. Well done Daniela and the very best of luck in your future studies!

Paul Smith Teagasc PhD Walsh Scholar

Paul is a long standing member of the BSAS Early Careers Council and is in the final year of his PhD at Teagasc. His PhD aims to determine a link between the rumen microbiome, host genetics and methane output in beef cattle. Paul is registered at University College of Dublin.