Gearing Up for the 2011 Breeding & Foaling Season!

There are several management tools used to bring about the onset of the breeding season or to alter the estrous cycle itself. The most reliable method used to induce the ovulatory season is the use of artificial lights to alter the mare’s perception of day length. The easiest light management program is to use lights at the end of the day to extend the perceived day length (or photoperiod) to 16 hours. This practice entails turning on an artificial light source 30 minutes before sundown. The light source should be turned on to supply enough additional light to produce a total 16 hours of daylight (natural and artificial), roughly until 11 pm. There is a lag period of 60 to 90 days between the onset of daylight extension and first ovulation. Therefore, if February-March ovulations are desired, mares should be started on the lighting program before December 15. If you are aiming for a January baby, most breeding sheds open between February 1st and February 15th, so you would need to start lighting programs no later than December 1st. 

Perception of day length must be constant from day to day; the use of automatic timers is of benefit. Also, using too much light can cause adverse effects. Mares that are exposed to continuous light may not cycle properly. Light intensity should be a minimum of two foot-candles, which is comparable to one 200-watt bulb for a 12 x 12-foot stall. Floodlights can be used on outside pens. A general rule is that lighting is sufficient if a newspaper can be easily read in any corner of the stall or pen. One side note is that mares in light inducement programs will also shed hair, so those housed outside will need protection from bad weather.

While the use of artificial lights has the greatest benefit on dry or open mares, recent studies have shown that early foaling mares will also respond to added light. Gestation lengths have been decreased by as much as 10 days when using lights for open mares, with no effect on foal weight and size. More importantly, artificial lighting enhances proper cycling in these mares after foaling.

Artificially advancing the ovulatory season in open and bred mares will help maintain a yearly foaling interval, produce older foals at the breed association’s January 1 universal birth date, and make better use of available semen across the entire breeding season.

"Ultimately Acoolest", colt by "Acoolest" out of "JNC Yella Tradition"
Owned by Kim Clark and photographed by Mark Clark