Influence of blue light applied to a single eye in mares during the cycling and pre-natal period
Creators: name: Cruz, Sofía Bazán Santa
name: Salgado, Joel Lucana
name: Lucano, Cintia Placencia
name: Chavarría, Roberto Pineda
Publisher: name: F1000 Research Limited
Year: 2017

description: In the present work, the effects of artificial photoperiod on cycling and gestation were evaluated according to three different investigations. In these studies, the mares were divided into samples to which a first group was given blue light applied to a single eye; to a second group, conventional white light in their respective colts, and to a third group, only natural light. The results of this experiment were effectively positive in the shortening of the transition period as well as the gestation period. There was also a notable influence on the weight increase of the foal, focusing on the Northern Hemisphere. It should be noted that the photoperiod is more influential in the mares (seasonal cycling) found in high latitudes, either north or south of the equator, since there the seasons are more marked.<br><br>The horses have a mating season that extends from April to September in the Northern Hemisphere, time that coincides with a longer duration of the day, grass growth and friendly climate. Mares are seasonal polyestrics. The main factor that regulates seasonality is the photoperiod. Melatonin is a pineal hormone produced during the hours of darkness, its pattern of light / dark mimicry segregation (and the hypothalamic-pituitary response) that occurs every 24h in the diurnal cycle, acts as a daily coder of temporal changes in the duration of the day and regulates the reproduction cycles by seasons in mammals. The animals perceive the changes in the daily duration of sunlight, which indicates the time of year in which they are. For this purpose, the light signal is transformed into endocrine signals by means of the pineal gland, which interacts with the hypothalamus, the pituitary and the gonads, to regulate the stages of reproductive physiology. Ovarian activity increases as light hours increase. It became an industrial standard practice to extend the duration of the day by 8-10 days exposing the females to artificial light until 11 o'clock, allowing natural dawn to occur during the most sensitive phase of the 24-hour cycle. An artificial photoperiod of 16 hours: 8 hours of darkness is facilitated by using the light of a 3.6x3.6m 100W energy light bulb described as "enough light to read a newspaper". A light therapy like this can advance the breeding season to an extension of 3 months. Recent studies indicate that light in the visible light spectrum (465-472nm) is more effective in inhibiting melatonin since melanopsin is particularly sensitive to blue lights, which have a short wavelength, of a diode led pointed directly at one eye. It aims to determine whether light, in a calculated time, of low intensity administered to a single eye from masks of light in females is as effective as the maintenance in closed environments of white light in the advance of the seasons of reproduction of the females As in other animals that reproduce seasonally, the photoperiod is also important for the pregnant mare. It has been found that the length of gestation decreases as the breeding season progresses and the duration of daylight is longer. From the studies, a significant shortening of the duration of gestation and a trend of greater birth weight of the foal was reported. The light administered to the pregnant mare can modify the maturation rate of the fetus during the final trimester. The birth weight of the foal is an important factor for horse breeders, since it has a perceived influence on the horse of potential gains and future athletic ability. Foals born later in the year (April, May and June), during the natural breeding season for the horse, have comparatively higher weights than foals born in January, February and March. Several studies have shown the effectiveness of artificial photoperiod programs to advance the start of the season of ovarian activity in mares in seasonal anestrus. In different latitudes of both hemispheres, studies have been carried out to evaluate various artificial photoperiod programs focused on decreasing the duration of the transition period towards the reproductive period.