An on-farm trial confirms that supplemental lighting boosts milk production of mature cows.

The study took place on a high-producing dairy in California’s San JoaquinValley. The trial began at 21 days in milk. Cows exposed to supplemental lighting received 17 hours of light and seven hours of dark.

The results, published in the December 2005 issue of The Professional Animal Scientist, show nearly an 8-pound increase in milk yield in mature Holsteins exposed to supplemental lighting versus mature herdmates exposed to natural lighting (12 hours of light). However, supplemental lighting had no effect on the milk yield of first-lactation animals. Feed intake did not differ for mature cows and first-lactation cows exposed to supplemental or natural lighting.


Milk production (pounds/head/day)


Supplemental lighting
(17 hours light)

Natural lighting
(12 hours light)

Mature cows



(2nd lactation or greater)


First-lactation cows