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Posted on 11-03-2014

Halloween’s over and we are approaching the “season of artificial lighting”! Nope, I’m not talking about all the Christmas lights that you’re planning to string up along the highest peaks of your house in the driving snow…’tis the season to start planning for next breeding season by starting your broodmares with a lighting program that will let you get a jump on the spring. Every year I receive numerous questions on the best artificial lighting programs—what works, why your friend thinks nothing works, why your husband thinks it’s too expensive, etc.  Read on to sort out myth from the reality of this useful tool.

Myth#1: Artificial lighting doesn’t work.

Wrong! Artificial lighting programs remain the best tool we have to hasten the onset of regular, ovulatory cycles in non-pregnant mares. The length of daylight is the primary stimulus to the mare’s brain which signals the release of a hormonal cascade resulting in the development of follicles and, ultimately, ovulation. It’s relatively cheap and easy and no medications or injections are required.

Myth #2: Artificial lighting works EVERY time.

Sorry, this is also wrong. Things can go wrong in a lighting program, or you may simply have one of those mares that fails to respond. While daylight is the primary stimulus, other factors like temperature and nutrition, can influence how well an individual mare will fare in a lighting program. It also requires dedication to the program—each mare, every day once started. If you have tried artificial lighting before with poor results, I hope this article can help you pinpoint any possible problems.

 And think you don’t need this because your mares reside in Florida? Think again—even sunny states like Florida, and as far south as Mexico City, still only check in with a little more than 14 hours of light on the longest day of the year: the same as Madison, WI!

Myth #3: You must start lights by November 1st.

Not true. Artificial lighting programs may begin anytime between early November and the winter solstice (this year occurring on December 21, 2014) or the shortest day of the year in the northern hemisphere. When planning your lighting regimen, consider the month in which you want to start breeding your mare. Artificial lighting shortens the winter anestrus period, but not the spring transition, so allow enough time to manage this phase. No idea what I’m talking about? Let me know! Maybe that should be the topic of another blog…

Myth #4: You can start lights after January 1st.

Nope, you can’t start lights late in winter and hope to advance your mare’s cycle.  It won’t hurt anything, but it is not going to help. Depending on the mare, her ovarian activity, and the owner’s budget, there are other options to try late in the winter. Ask your vet. Your REAL vet, not Dr. Google…

Myth #5: Artificial lighting must be done in a stall.

It is certainly easier to control a lighting program if your mare comes into a stall at night, but if she lives outside you can still keep her under lights with a few adjustments.  A brightly lit (see Myth #6) paddock, without shadowy corners to hide in, can be successful.  Recently, researchers have developed a blue light head mask to allow mares to stay outdoors yet stay on a lighting protocol. 

Myth #6: You need a special type of light bulb.

Not really.  Light in the blue light spectrum (as in the mobile mask above)has been found to be more effective in some other species, but the most important feature of the lighting regimen is how many foot candles or lux (standard international unit of illuminance) are generated by your light bulb.  The easy rule of thumb is this: if you can read newsprint in the darkest corner of the stall, you have enough light (yes, you can use your glasses if you are over 45!).  If you are the tech-y type, and want to be absolutely certain that you have enough light, you can use your DSLR camera to measure the light.  Google can give you the specifics.  Your goal is approximately 10 foot candles or 108 lux.  

Myth #7: You must have the lights on all the time.

Absolutely incorrect! This is one of the exceptions to the “more is better” rule. In fact, mares that are exposed to lights 24/7 usually shut down.

Traditional lighting protocols call for 16 total hours of light per day for maximum effect. Adding light in the morning before sunrise is not as effective as adding light after sunset. This regimen works well for many owners who bring their mares into a stall at night, but the system will require some weekly “tweaking” as day length changes so that you consistently have 16 total hours of light. And be prepared for an increase in your electricity bill!

The “flash method” (aka pulse lighting or night interruption) is also effective and energy saving. In this protocol, mares are exposed to a 2 hour period of light after 9 hours of darkness. For example, if it is dark outside at 5pm, lights should turn on in the stall (easy to do with an automatic timer) from 2am-4am and then turn off for the remainder of the night. Besides the advantage of using less electricity to light the stalls, this method is more flexible to human schedules. Not going to be home at dark to bring the horses in? No problem with the flash system, since light is only required in the middle of the night. The drawback to this method is that most of us are not up at 2am to check that the light timer is functioning or that the light bulb hasn’t burnt out. I use this method here at EFS and check bulbs and timers weekly.

Myth #8: Lighting programs are only for broodmares.

Although the effect hasn’t been studied as much, artificial lighting programs can be beneficial for stallions, especially if subfertility is a problem. Like mares, stallions also experience a seasonal influence on the reproductive system. Sperm count, motility, ejaculate volume, and total scrotal width are just a few of the semen parameters affected by day length in the stallion. As long as you follow the basic guidelines for adding artificial lighting (no 24/7 lights please!) you will do no harm, and may help your subfertile stallion especially early in the season.

Myth #9: Lights will help my pregnant mare to foal earlier in the spring.

Regrettably, no. There is little evidence that subjecting pregnant mares to artificial lighting has any effect on foaling date. But it certainly does no harm, so if you have a mixed barn (pregnant and open mares) you can safely use lights for the open mares without hurting the pregnant ones.

That’s all the myth-busting for this blog. Have more questions? Got any comments about your experience with lighting protocols? Suggestions for other blog topics? We would love to hear from you! 

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