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Image by Kelly Forrister


FARM-LED lighting systems


The horse is an animal with a seasonal poly-estrous cycle which, after a period of absence of heat (seasonal anestrus), usually begins to show heat in spring, when the days get longer.

In some cases it may be possible and convenient to anticipate the estrus of the fillies or mares left empty the previous year by applying the so-called light program, which acts by changing the photoperiod.


To simulate the arrival of spring, the photoperiod is artificially altered, starting to gradually increase the hours of light with artificial lighting.

Since it usually takes 45-60 days of treatment before the mare demonstrates heat, in order to have the mares in heat in late January, early February, the right time to start the light program is therefore from mid-November to mid-December.


There are two application possibilities for the photoperiod:

  • CONSTANT PHOTOPERIOD: The most used program is the one that provides for 14 ½ to 16 hours of continuous light every day. In the event that the mare is grazing, it must be brought to the stable and placed under light just before sunset. If a constant light regime is used, the lamps should be turned on at 4.30pm and off between 10pm and 11pm for all days of the 10 weeks preceding the scheduled insemination date.

  • GRADUAL PHOTOPERIOD: in the case of a gradual light program, add 3 hours of light the first week and ½ every additional week until 15-16 hours per day are reached.



Pregnant mares that are exposed to 16 hours of light during the latter part of their gestation give birth on average 7-10 days earlier than those that have not. What's even more interesting is that if you plan to re-fertilize your bitch after giving birth, the light program prevents her from eventually going into anestrus, as often happens to those mares that give birth in the early part of the year.

In addition, the administration of light (long photoperiod) during the pre-calving period results in a shorter gestation, a higher foal weight at birth and better coat condition of the foals.

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