Article

Efficiency of Equilume Light Mask on the Resumption of Early Estrous Cyclicity and Ovulation in Thoroughbred Mares

Seongmin Kim1, Heejun Jung1, Barbara Murphy2,*, Minjung Yoon3,**
Author Information & Copyright
1Department of Animal Biotechnology, Kyungpook National University, Sangju 37224, Korea.
2School of Agriculture and Food Science, University College Dublin, Dublin D04 V1W8, Ireland.
3Department of Horse, Companion and Wild Animal Science, Kyungpook National University, Sangju 37224, Korea.
**Corresponding Author: Barbara Anne Murphy, School of Agriculture and Food Science, University College Dublin, Dublin D04 V1W8, Ireland. Phone: +353)-01-716-7717. E-mail: barbara.murphy@ucd.ie.
**Corresponding Author: Minjung Yoon, Department of Horse, Companion and Wild Animal Science, Kyungpook National University, Sangju 37224, Korea, Republic of. Phone: +82-54-530-1233. E-mail: mjyoonemail@gmail.com.

© Copyright 2021 Korean Society of Animal Science and Technology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Sep 08, 2021; Revised: Nov 04, 2021; Accepted: Nov 04, 2021

Published Online: Nov 23, 2021

Abstract

Previously, Equilume light masks had no impact on hastening the resumption of estrous cyclicity in mares maintained in outdoor pastures on the mainland of South Korea due to the cold weather conditions. Jeju Island is a major horse-breeding site in South Korea and is warmer than the mainland during the winter season. Therefore, the primary objective of this study was to explore the efficiency of the Equilume light mask on the resumption of seasonal estrous cycles in Thoroughbred mares on Jeju Island. A total of 20 nonpregnant mares were randomly divided into the Equilume light mask (n = 9) and stable lighting (n =11) groups. The experiment was performed at seven different horse-breeding farms located on Jeju Island from November 15, 2020, to February 15, 2021. The mares were exposed to the respective lights from 16:00 to 23:00. Follicle size and uterine edema were measured by ultrasound scanning. Body conditions scores were also monitored during the experiment. Statistical analysis was conducted using the SAS and SPSS software, and <italic>p</italic>-values of &lt;0.05 were considered statistically significant. Two of the nine (22.2%) mares in the Equilume light mask group and three of the 11 (27.28%) mares in the stable lighting group were still cycling in December and January, which were considered as all-year-round cycling mares. On February 15, there was no difference between groups in the resumption of early seasonal estrus cycle, which was determined by follicles &gt;25mm in addition to uterine edema. 100% of the Equilume light mask group and five of the eight mares (62.5%) in the stable lighting group had resumed cycling. Interestingly, six of the seven mares (87.5%) in the Equilume light mask and four of eight mares (50%) in the stable lighting group had already ovulated on February 15 (<italic>p&gt;0.05), </italic>as determined by the presence of a recent corpus luteum. No difference was observed in BCS and uterine edema between groups (<italic>p</italic>&gt;0.05). In conclusion, the Equilume light mask can be an effective approach to induce early seasonal estrus cycles of mares, and it also enhances the efficiency of farm management by reducing labor.

Keywords: Blue light; light mask; reproduction; early seasonal estrus cycle; mare; welfare