Short-day lighting — eight hours of light followed by 16 hours of darkness — improves immune function in dry cows, according to research reported in the November 2004 Journal of Dairy Science.

During the study, the growth of immune cells called lymphocytes was greater in dry cows exposed to short-day lighting compared to dry cows exposed to long-day lighting. This was true for the entire 62-day dry period and into the first few days of lactation.

The improved immune status of dry cows exposed to short-day lighting may help them respond faster to health challenges at calving.