I Don't Get It

The final passage of the Energy Bill extends Daylight Savings by 4 weeks instead of 8 weeks. I prefer the longer version - or even a permanent DLS - but will take what I can get. The news article discussing the bill had this:

Farmers said the change would adversely affect livestock.

Huh?

DLS is nothing more than a mass rescheduling of the day. Think if it as working 8-4 instead of 9-5. School goes from 7-2 instead of 8-3. So if you are retired and don't work, don't have kids to prepare for school, own a Tivo, and shop at stores that are open 24/7 (or on-line), DLS has little affect on your life.

Farmers - and cows - set their own hours. Except for occasional market events like auctions and the like, how does DLS have any change on livestock? The farmer can decide when he is going out to the barn and milk. Can someone out there fill me in, or is this just a silly argument?