Long Daylighting (Photo-period Control)

When cows are exposed to long days, 16 to 18 hours, research has shown that they will give 4 to 5 pound more milk per day. Long days can be created by exposing the cows to artificial or a combination of natural and artificial light. In a tiestall barn this can be accomplished by installing a row of LED tube, T-8 or T-5 fluorescent fixtures over the feed alley. In a freestall barn, LED, metal halide or high pressure sodium lamps are normally used unless the ceiling height is less than 10 feet, then LED or high output T-8 fluorescent fixtures would likely be recommended. Long Day lighting will generally not work for farms milking 3X because it is nearly impossible to achieve 6-8 hours of darkness due to milking schedules. It might be possible to achieve for a select number of groups but likely not the entire herd.

For more information, refer to the following links:


If you have questions about the information on this site, please contact
Scott Sanford, Distinguished Outreach Specialist, University of Wisconsin, sasanford@wisc.edu.