Current Progressive Dairy digital edition

0309 PD: Is there enough light in the calf house?

Neal Broadwater Published on 06 February 2009
There have been numerous scientific studies that have shown exposing lactating dairy cows to a long-day photoperiod (LDPP – 16 to 18 hours of light and six to eight hours of dark) in a 24-hour period improves milk production and reproduction performance, that this response persists through an entire lactation, perhaps increasing milk yield as much as 8 to 10 percent. This management practice, called photoperiod manipulation, uses a designed lighting system to artificially extend the duration of light that a lactating cow is exposed to especially during the fall, winter and spring seasons of the year.

Photoperiod studies have also been conducted on dry cows. A study by dairy scientists from Vermont, Illinois and Clemson as well as a study at the University of Maryland found that exposure to a short-day photoperiod (SDPP – eight hours of light and 16 hours of dark) during the 60-day dry period was a management practice that increased milk yield of cows in the subsequent lactation.

What about photoperiod manipulation in raising dairy calves and heifers? Several studies have been conducted in recent years that show some promise to consider this management practice at least up through puberty.



• An Illinois study found that heifers exposed to LDPP enhanced bodyweight, wither height and heart girth, and reached puberty 24 days earlier than SDPP heifers without adversely affecting frame growth or mammary development.

• Another Illinois study found that heifers on LDPP during the prepubertal growth phase had 1 inch greater wither height and 121 pounds more bodyweight at calving compared to SDPP heifers, and tended to produce more milk during the first lactation (1,654 pounds over 305-day projected fat-corrected milk).

• Research at the University of Guelph in Ontario, published in the Journal of Dairy Science, shows LDPP calves were heavier at 56 days of age compared to calves given only 10 hours of light and 14 hours of dark. The LDPP calves consumed 78 percent more starter than the SDPP calves and this stimulated faster rumen development in the LDPP calves.

If photoperiod manipulation is being considered, it is recommended that lighting have a color rendition index (CRI) of greater than 80. Light intensity of at least 100 lux (9.3 foot-candles) seems to be necessary. Note: Light is measured as foot-candles (lumens per square meter) or lux (lumens per square foot). There are 10.76 lux (lx) in 1 foot-candle (ftc). For calves, use incandescent, halogen, fluorescent and metal halide lamps. Avoid high-pressure sodium and mercury vapor lamps.

• Heifers on LDPP from weaning to puberty grow at a faster rate and tend to be leaner than those on SDPP. Most of the growth increase is in frame height. The LDPP heifers remained taller when height was followed through to calving. Dr. Geoff Dahl, University of Florida, states that because height is more strongly correlated to future production than weight, this early growth response should be an advantage.


• Starting LDPP treatment at or before weaning is ideal. Heifers should remain on LDPP until puberty. Results of LDPP following puberty have been inconsistent.

• An 8-hour dark period is needed to stimulate the photoperiod management response.

• Hours from sunrise to sundown changes throughout the year, from 8 hours, 50 minutes on January 1 to 15 hours, 33 minutes on July 1 (Minneapolis, Minnesota in 2004,

• Consider SDPP for bred heifers during the two months before freshening, as is the case for dry cows, to maximize production in the next lactation and enhance immune function in the transition period.

• There is some emerging data suggesting that immune function is influenced by photoperiod. According to Dahl, these data support the concept that an animal’s environment can affect performance as well as health and well-being.

Would photoperiod manipulation be beneficial to you in raising dairy calves and heifers? First, do you have a calf-raising facility where the photoperiod can be manipulated? It may be hard to accomplish if using outside hutches and pens. Secondly, the economic benefit needs to be determined weighing the investment in more and better lighting, if that is the case, additional cost for energy and any other costs against any of the benefits of growth desired.


Thirdly, Hugh Chester-Jones, Animal Scientist at the Southern Research and Outreach Center in Waseca, Minnesota, cautions that we need to recognize many other variables including calf comfort, nutrition and environmental interactions will affect the magnitude of the photoperiod response as well, so one needs to understand what photoperiod manipulation would do for your dairy replacement enterprise. PD

References omitted but are available upon request at

—Excerpts from University of Minnesota Dairy Connection, September 2008

Neil Broadwater
Dairy Extension University of Minnesota