Photoperiod management of dairy cattle: considerations and applications

Abstract Text: Photoperiod, the duration of light exposure relative to darkness in a day, has significant impact on productivity and health of dairy cattle and other farmed species.  A light:dark cycle of 16 hr light and 8 hr dark (16L:8D) is termed a long day photoperiod, whereas a 8L:16D cycle is termed a short day photoperiod.  The physiological basis for the response begins with light perception at the eye and signaling to the hypothalamus and pineal gland to alter secretion of melatonin.  Circulating melatonin increases during exposure to darkness from concentrations that are typically undetectable, and thus the lighting schedule drives a pattern of melatonin release that allows the animal to track daylength.  The most consistent endocrine effects of variable photoperiod are the responses of circulating prolactin and insulin-like growth factor-1, both of which impact growth and mammary gland function throughout the life cycle.  Specifically, long day photoperiod increases lean growth in heifers, and increases milk yield in lactating cows.  In contrast, cows maintained on short days during the dry period subsequently produce more milk than those on long days when dry.  Cows on short days when dry and those on long days in lactation have increased dry matter intakes relative to herdmates on the respective opposite treatments.  Managing lighting in barns is easily implemented with commonly available fixtures and lamps.  Indeed, the choice of light installed is made by combining the highest efficiency lamp available for the effective mounting height of the barn.  Typically, with lower ceilings a compact fluorescent lamp is the most appropriate selection, whereas the higher mounting heights available in free-stall barns are better suited to metal halide or similar high efficiency lamps.  Recently, LED lamps have been recommended due to their superior energy efficiency, but direct, robust testing of LED lamps has not been reported.  Low intensity red lighting can be used in facilities during darkness as it is not perceived as light by many species including cattle.  Target light intensity is in the range of 150 lux at a level 1 meter above the floor of the barn, and that intensity should be maintained throughout the facility.  Photoperiod manipulation is a low cost, high return method to increase the productivity of the dairy herd throughout the life cycle of the cow.

Keywords: Photoperiod, dairy cow, housing