Light

Researchers have found that increasing light from less than 12 hours/day to 16-18 hours/day, increases milk production by 7-10%. It is critical for the response that cows have an uninterrupted dark period. Bovine somatotropin(bST) and long-day lighting increase IGF-I independently so using bST and long-day lighting together will still pay. Daily light has also been found to impact dry cows. In the growing heifer, long-day lighting has been found to increase gain, feed efficiency and growth of mammary parenchyma. The experts claim that long-day lighting is very economical and increases income by $0.24 to 0.35/day/cow. Daylight varies with season. In many milk-producing regions of the world, there are a number of months when daylight is less than 12 hours/day. Researchers have shown that controlling and supplementing the amount of light a cow receives each day can increase milk production.

Long-day lighting (or long-day photoperiod) means that cows have 16 hours of light and 8 hours of darkness each day. Researchers have found that increasing light from less than 12 hours/day to 16-18 hours/day, increases milk production by 7-10%. Milk composition is usually not affected, although some have reported small reductions in milkfat percentage. Long-day lighting usually increases dry matter intake (up to 6%) to supply the extra nutrients needed for milk production. The initial response takes about 2-4 weeks to be seen.

It is critical for the response that cows have an uninterrupted dark period. Cows under continuous light have production levels similar to cows that don’t have enough light. Dim red bulbs (7.5 watt bulbs at 20-30 foot intervals) can be used during the dark period if cows must be moved or observed during that time.

How Can Light Increase Milk Production?

Melatonin is a hormone produced in the cow’s pineal gland. When light hits a cow’s eye, it signals the cow’s body to produce less melatonin. When it is dark, melatonin is produced. Cows have an internal clock that is set by melatonin production. This internal clock affects the production of other hormones that impact milk production. Long-day lighting increases the production of IGF-I (insulin-like growth factor - I). IGF-I is the same hormone that is increased by bovine somatotropin (bST). More IGF-I production in the cow boosts milk production.

Where’s the Research?

Researchers at the University of Maryland used 40 lactating cows for an 84-day trial. Twenty cows received no supplemental light (<13 hours of light per day) and 20 cows received 18 hours of light and 6 hours of darkness. Fat-corrected milk production was 4 pounds/day (1.8 kg) higher with supplemental light (83.2 vs. 79.2 pounds/day (37.8 vs. 36 kg)). IGF-I levels were increased from 60.1 ng/ml to 52.6 ng/ml. There was no change in milkfat concentration and no change in dry matter intake.

Bovine somatotropin(bST) and long-day lighting increase IGF-I independently so using bST and long-day lighting together will still pay. They have an additive effect. University of Maryland researchers tested the effect of bST and long-day lighting on 40 lactating cows for 140 days. Normal hours of daylight during the study ranged from 9.5 to 14 hours/day. Treating cows with bST alone raised 3.5% fat-corrected milk production (FCM) by 12.54 pounds/day (5.7 kg) from 60.9 to 73.48 pounds/day (27.7 to 33.4 kg). Using long-day lighting increased FCM production by 4.2 pounds/day (1.9 kg), from 60.9 to 65.1 pounds/day (27.7 to 29.6 kg). Using both bST and long-day lighting increased milk production by 16.9 pounds/day (7.7 kg) from 60.9 to 77.88 pounds/day (27.7 to 35.4 kg). The researchers also found that the cows on long-day lighting met their extra nutrient needs by increasing dry matter intake. Cows on bST increased intake more quickly following their initial injection if they were also treated with long-day lighting.

Daily light has also been found to impact dry cows. In one study, cows that received only 8 hours of light per day during the dry period produced 6.8 pounds (3.1 kg) more milk per day during their first 120 DIM than cows that received 16 hours of light per day during the dry period. At freshening, all cows just had ambient lighting (9.5-10.5 hours of light per day). The reason for this response is not fully understood but some have suggested that the short-day lighting during the dry period may make cows more responsive to the positive influence of longer day lighting once they calve. It is also interesting to note that during the dry period, those cows which only had 8 hours of light per day ate 12% more dry matter. The reason for this is unknown but it did result in more energy reserves available for these cows after calving. More research needs to be done on light regulation in dry cows.

In the growing heifer, long-day lighting has been found to increase gain, feed efficiency and growth of mammary parenchyma. One study with long-day lighting (16 hours) increased heifer growth rate by 10%. It is interesting that this extra growth is not just a function of extra dry matter intake. Long-day lighting also results in earlier onset of puberty.

Providing the Light Your Cows Need:

The intensity of the light which cows are exposed to is as important as the length of the lighting period. A minimum of 20-30 foot-candles is recommended. Twenty to 30 foot-candles would be enough to read by. Good office lighting is generally about 35-50 foot-candles. Sunny days may be greater than 1000 foot-candles.

A Wisconsin study showed that average light intensity in the feeding area of freestall barns was 14.23 foot-candles and ranged from 2 to 38. In the freestall area, light intensity ranged from 0.1-100 foot-candles and averaged 7.3 foot-candles. Average feeding area lighting in tie-stall barns was 20.35 foot-candles and ranged from 14.7-26. We know from research studies that cows spend about 10-15 hours/day resting and 4-5 hours/day eating. So, for long-day lighting to work, both the resting and eating areas must be provided with adequate light.

Light meters can be purchased from electric supply stores to check to see if your light is right. Remember that dust and age of light bulbs can reduce the actual amount of light received by cows. Check light distribution. Barns with rafters are difficult to light and may need more fixtures to get good light distribution. One recommendation is to have the distance between fixtures at 1.2-1.8 times the mounting height. Use a timer to insure proper timing and save on labor.

Total Lumens Needed

= [Area (sq. ft of barn) x (20 foot candles needed) x Barn Constant* (2 or 3)]

*Barn Constant = 3 for open-sided or curtain-sided barn, 2 for a barn with light walls that reflect light)

Total Fixtures Needed

= (Total lumens/Lamp lumens)

Example: (56x112 ft open-sided freestall)

Total Lumens =

(6272 x 20 x 3) = 376,320 lumens

Total Metal Halide Fixtures =

(376,320/20,500) = 18 fixtures

(Source: G.E. Dahl, Hoard’s Dairyman, 1998)

WattsLampLumens
  High-pressure Sodium Metal Halide
400 50,000 36,000
250 27,500 20,500
150 16,000 14,000

What Are The Economics?

The experts claim that long-day lighting is very economical and increases income by $0.24 to 0.35/day/cow. But, it’s a good idea for individual producers to calculate their own lighting costs and compare milk production before and after long-day lighting. It is also important to account for feeding changes and changes in days in milk that may have also occurred during the experimental period.

Supplemental Lighting Balance-Sheet Example
  Daily Income/Cow Daily Expenses/Cow
8% Milk Increase (65 to 70 lbs/day), $13/cwt $0.65  
0.10 decrease in fat, $0.80/lb. fat   $0.08
6% increase in feed ($3.25 to $3.45)   $0.20
Light (0.7 – 2 Kwh @ $0.07/Kwh)   $0.05-$0.14
Total $0.65 $0.33-$0.42
Difference $0.23-$0.32  

Source: Tucker, 1997

In 2000, a study was performed at the University Maryland to address the effects of photoperiod manipulation on dry cows. Basically, the study showed that when dry cows are housed under the now conventional practice of 16 hours of light and 8 hours of dark, they produced about 7 lbs less than cows housed under the opposite scheme (8 h light, 16 h darkness) in their subsequent lactation. Typical of a lot of research, this study presents more questions than it answers. However, it definitely shows that this is an area worthy of further research to determine exactly why this response was seen.

One school of thought is that the well-documented milk response to extended daylength periods loses it effect after a while, if there is no rest period. If this is true, housing of dry cows becomes an important issue. To see a favorable response to longer daylength requires housing that curtails ambient light without compromising ventilation. Housing that incorporates mechanical ventilation and light traps is required. In hot weather, cooling fans will also be required. The current recommendation is that the short light period should be sustained for the entire dry period. Further research may show a response to shorter treatment periods, which would be beneficial in practical situations. Most farms are set up to handle dry cows with either open-air facilities or pasture, neither being a situation that would allow for photoperiod manipulation. The most practical solution for most farms is probably keeping dry cows housed under natural light conditions and extending the day length period of milking cows all year round. This should still achieve the benefits of photoperiod manipulation without having to invest in a large change of housing and management for dry cows. In addition, it may not be necessary to purposefully manipulate day length during the late winter to early summer period, since days are naturally lengthening at that time anyway.

Preliminary estimates of the economics of photoperiod manipulation for dry cows seem to be favorable. However, conditions will change from farm to farm. Each farm requires a thorough evaluation before implementing such a change.

References:

Dahl, G.E. 1997. Adjusting photoperiod may boost milk production. Feedstuffs. November 10, 1997, p. 12.

Dahl, G.E., T.H. Elsasser, A.V. Capuco, R.A. Erdman, and R.R. Peters. 1997. Effects of a long daily photoperiod on milk yield and circulating concentrations of insulin-like growth factor 1. J. Dairy Sci. 80:2784.

Dahl, G.E. 1998. Controlling barn light makes more milk. Hoard’s Dairyman. October 10, 1998, p. 683.

Dahl, G.E., B.A. Buchanan, and H.A. Tucker. 2000. Photoperiodic effects on dairy cattle: A review. J. Dairy Sci. 83:885.

Dahl, G. E. 2001. Photoperiod control improves production of dairy cows. Feedstuffs. June 11, 2001, p. 10.

Miller, A.R.E., E.P. Stanisiewski, R.A. Erdman, L.W. Douglass, and G.E. Dahl. 1999. Effects of long daily photoperiod and bovine somatotropin (Trobest) on milk yield in cows. J. Dairy Sci. 82:1716.

Posson, I., S. Gunderson, and J. Keuning. 2000. Light up your milk production. Hoard’s Dairyman. May 25, 2000, p. 386.

Pritchard, D.E. 2000. Photoperiod work on heifers and dry cows looks good. Hoard’s Dairyman. October 25, 2000.

Stanisiewski, E.P. and H.A. Tucker. 1986. Supplemental light increases milk yield in Michigan dairy herds. MSU Extension Bulletin E-2013, November, 1986.

Tucker, H.A. 1997. Light up your cows. Michigan Dairy Review. Vol. 2, No.1.

Lighting up your cows' lives. Northeast Dairy Business, November, 2001.

Gooch, C.A. 2002. Turn the lights out on dry cows. Northeast Dairy Business. July 2002. p. 20.

Related Links:

Dairy lighting system for tie stall barns
J. Chastain and R. Nicolai, Clemson University
Comprehensive article covering light design for tie stall barns. Focuses on the calculations needed to determine fixture type and dimension. Many useful tables for those looking to design a lighting system. Maybe an older article as it only includes information for incandescent, fluorescent and halogen lighting.

Responding to the Practical Implications of Dry Cow Photoperiod Research.
Rodenburg, J. 2002.

Authors

F.A.R.M.E. Institute

F.A.R.M.E. Institute

FARME Institute's goal is to provide top quality, client-oriented, independent and confidential research and product development in ruminant nutrition.

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