Long days= more milk

So my mind has rambled and come across a topic for this week.  The impact of photo-period on milk production in lactating dairy cows.   Photo-period (the length of the day) effects many organisms in many different ways.  Examples are flowering in plants and migrations in birds.  The length of our days changes because the earth's axis is tilted in relation to its' orbit around the sun.  This results in the northern hemisphere having longer days in May, June, and July and shorter days in November, December and January.  The opposite occurs in the southern hemisphere.  This year our (northern hemisphere) longest day was June 20 and lasted 15 hours 23 minutes the shortest day will be December 21 only lasting 8 hours 58 minutes.  That's a total difference of over 6 hours of light (6 hours 25 minutes to be exact).

Photo credit Trevor Beaudry

So big deal why is the kid that plays with cows talking about the differences in daylight between June and December? 

Well interestingly photo-period impacts milk production.  Not just a little bit like calf sex that we talked about a little bit ago, but something like 5-15%.

Pause for dramatic effect

Day length impacts the milk production of a cow by 5-15% 

Ok that was a bold statement I'll make it a little clearer.  Say your cow is producing 20,000 lbs of milk a lactation and that by exposing her to the optimal amount of daylight for the entire lactation her production increased 5%.  That is an increase of 1,000 lbs of milk.  A serving of milk is 8 ounces ( visualize the cardboard cafeteria milk containers) that's an extra 2,000 servings of milk by doing nothing but adjusting the lights.  




Okay I understand the benefit but how do I achieve that/ it must be hard or everyone would do it? 

Well no not exactly. 

All the lactating cow requires is whats referred to as long day photo-period (LDPP).  That is 16 hours of continuous light followed by 8 hours of continuous dark.  The keyword is continuous if you turn the lights on in the middle of the dark period it undoes all your gains.   

Sounds simple enough but I have a busy life and may not be able to always turn the lights on and off at exactly the right times. 

Lucky for our busy farmer friend you can simply set the lights on a timer and never have to worry about turning them on or off (or realizing that they are still on when you finally sit down for supper).  Interestingly enough there are often farms where the lights stay on for over 16 hours a day that can save money on electricity and gain milk production by taking advantage of LDPP.

Photo by Trevor Beaudry

Maybe she'll benefit from LDPP someday. (like how I cunningly justified the gratuitous picture of the cute calf?) 


Management of photoperiod in the dairy herd for improved production and health. G. E. Dahl and D. Petitclerc