Mrs. Dianne Shoemaker, Extension Dairy Specialist, OSU Extension Center at Wooster
Increased milk production of 5 to 10% is a well-documented response by lactating dairy cattle to controlled lighting. For lactating cows, 16 hours of light followed by 8 hours of dark elicits this response. This simple strategy is a cost-effective method of increasing income per cow.
Estimates of annual profit range from $4400 to $10,400 (at milk prices of $9.50 and $14.50 per cwt., respectively) in an 80-cow tie stall facility (Dahl, 2001). Estimates for a 250 cow freestall barn range from $24,000 to $43,000 for the same milk prices. These calculations include increased milk income, feed intake and electricity use. They do not include the potential initial investment in additional lighting needed in some barns.
Continuing research is increasing our understanding of the mechanisms behind the increase in daily milk yield. Light hitting the cow's eyes signals the cow to suppress release of the hormone melatonin. Longer periods of light, such as the 16 hours of light recommended for lactating cows, means shorter periods of time of high melatonin levels.
These shorter periods of higher melatonin levels then impacts the levels of prolactin and IGF-1 (used as an indication of immune system response) circulating in the cows' blood. Over the course of a few weeks, this chain of events causes the cow to increase milk production. Increased feed intake follows to support the increased milk production.
For lactating cows, a minimum of 6 hours of uninterrupted dark is recommended for cows milked 3X per day. Eight hours of uninterrupted darkness is optimal for cows milking 2X. Low wattage (7 to 15 watts,) red incandescent lights can be used when moving cows to and from the parlor in 3X situations to help achieve 6 to 8 hours of uninterrupted darkness. These lights provide adequate illumination to work the cows but are not perceived as "light" by the cows.
Recent research at the University of Illinois (Hall et al., 2005) is exploring the impact of controlled lighting in the dry period on milk production in the following lactation. Cows receiving 8 hours of light (SDPP, or Short Day Photo Period) and 16 hours of dark for the full dry period achieved higher production in the following lactation than control cows housed in ambient (naturally occurring) lighting conditions.
A 2-year study at the University of Maryland, (Miller et al., 2000), documented a 7 lb increase in milk production for the first 16 weeks of the following lactation for cows receiving the SDPP treatment during the dry period compared to cows exposed to long-day photoperiods (LDPP). Interestingly, their hypothesis was that the LDPP dry cows would out-produce the SDPP dry cows!
In this study, all cows were housed together in ambient (naturally occurring) lighting conditions after calving. The benefits of the dry period lighting conditions carried forward into the following lactation.
More recently, heifers housed in SDPP conditions for the last 60 days of gestation also showed increased production in their first lactation compared to heifers housed in ambient lighting conditions. It is not yet clear if their response is as great as older cows.
Current research results indicate that the SDPP is needed for the full dry period. The increased milk production response was not seen in animals receiving the SDPP for only 21 days prepartum. Peticlerc et al. (1998) also found that simply supplementing cows and heifers with melatonin during the dry period did not increase production in the following lactation.
Restricting light to dry cows and pre-fresh heifers is not an easy management practice to implement. In naturally-ventilated buildings, it may be nearly impossible in all but the winter months. However, it may be a realistic way to achieve a controlled lighting response on farms where 3X or 4X milking practices make it difficult to achieve a continuous 6 to 8 hour period of darkness for lactating cows.
When considering new construction, can this practice be economically implemented? Restricting light to 8 hours per day narrows housing options to enclosed, mechanically ventilated facilities nearly year-round. Typically, these structures will increase housing costs. Actual costs at the individual farm level should be weighed against the potential increase in milk production from controlled lighting.
Additional information about controlled lighting, an example lighting system design and calculations can be viewed at http://www.trail.uiuc.edu/photoperiod/ .
Dahl, G. E. 2001. Update on photoperiod management of dairy cows. Proceedings of the 4-State Applied Nutrition and Management Conference. pp. 139-142.
Hall, E.H., T.L. Auchtung-Montgomery, G.E. Dahl, and T.B. McFadden. 2005. Short Communication: Short-day photoperiod during the dry period decreases expression of suppressors of cytokine signaling in mammary gland of dairy cows. J. Dairy SCI 88:3145-3148.
Miller, A.R.E., R.A. Erdman, L.W. Douglass, and GE Dahl. 2000. Effects of photoperiodic manipulation during the dry period of dairy cows. J. Dairy SCI 83:962-967.
Peticlerc, D., C.M. Vinet, G. Roy, and P. Lacasse. 1998. Prepartum photoperiod and melatonin feeding on milk production and prolactin concentrations of dairy heifers and cows. J. Dairy SCI 81 (Suppl.1):251.