Research from the University of Guelph in Ontario, Canada, shows calves exposed to 18 hours of light followed by six hours of dark were heavier at 56 days of age compared to calves given 10 hours of light followed by 14 hours of dark.

Average daily gain from 29 to 56 days of age was nearly three-fourths of a pound greater for the long-day calves. They also ate more starter per calf per day than the short-day calves. (Please see the chart below.) That, say the researchers, “stimulated faster rumen development” in these calves.

During the study, the researchers used fluorescent lights to achieve a lighting intensity of about 600 lux at eye level. Study results can be found in the November 2007 Journal of Dairy Science.