Long day induced increases in milk yield occur when intensity of light is at 20
to 30 foot-candles at eye level of the cow. Intensity of light can be measured
with a handheld light meter. Lamps should be placed over the cows' heads where
they spend the most time. Therefore, the cubicles, not the feed passage, should
be the primary area lighted. "Head to head" rows of cubicles can be
lighted with a single row of lamps. The feed passage may be lighted, but this
involves increased costs of installation and operation of additional lamps. It
is not necessary to have 20 to 30 foot-candles of light in every nook and cranny
of the facility. Remember, as height of the lamps above the cows' heads
increases, a greater area is lit, but intensity of light decreases. Periodically
cleaning lamps is essential to maintaining intensity of light.
· Fluorescent lamps are recommended only for houses with low ceilings such as
found in many kennels. In cold house the fluorescent fixture should be equipped
with a high output, rapid start, dust and moisture resistant, -20 degree
· Metal halide / High Pressure Sodium lamps are recommended for houses with
high ceilings such as usually found in cubicle house.
· Though more expensive, lamps equipped with a reflector and refractor are more
Lights and bST
Long day photoperiods combined with bST additively increased milk production
(2). Increased milk production occurs within a few days after bST treatments are
initiated; whereas long day induced increases in milk yield require several
weeks of exposure. In confirmation of Michigan's earlier work, long day
photoperiods increased dry matter intake in these more recent studies. Indeed,
long day photoperiods may stimulate feed intake earlier in cows treated with bST
as compared with bST alone.
Lights and 3X milking
There have been no reports comparing light induced and 3X milking induced
increases in milk yield, although there is no apparent reason to believe that
milk yield would not increase, at least additively, to a combination of both
management practices. A troublesome problem with a combination of long days and
3X milking is supplying a sufficient number of hours of darkness. One approach
may be to offset the lighting schemes in separate pens so that different pens
receive darkness at different times of the day. The principle should be to
coordinate exposure to lights with routine feeding, management, and milking
practices. Placement of 4 Watt red incandescent lamps 20 to 30 feet apart along
walkways can be used to assist with movement of cattle in the dark.
Lights and the Dry Period
Surprisingly, new research shows that exposure to long day photoperiods during
the dry period reduces milk yield in the subsequent lactation by more than
5L per day in comparison with cows given short day photoperiods (8 hours
of light: 16 hours of dark) (3). Perhaps cows eventually become refractory to
continuous exposure to long days in the previous lactation, and exposure to
short days during the dry period resets a cow's responsiveness to the
stimulatory effects of long days during the subsequent lactation. Depending upon
accommodation, the dry period would be an ideal time to expose dairy cows to
short day photoperiods in order to stimulate subsequent milk production.
1. Dahl, G.E., et al. 2000. J. Dairy Sci. 83: In Press.
2. Miller, A.R.E., et al. 1999. J. Dairy Sci. 82: In Press.
3. Miller, A.R.E., et. al. 2000. J. Dairy Sci. 83: In Press.
4. Peters, R.R., et al. 1978. Science, 199:911.
5. Peters, R.R., et al. 1981. J. Dairy Sci. 64:1671.
Michigan Dairy Review, Vol. 2: 7, February 1997.
Dairy Review, Vol. 5: 1, January 2000
Acknowledgement: Adapted from the
Michigan Review article see page 7 - If you do not have the free
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