Despite what the usually reliable Cecil over at the Straight Dope has to say, dairy farmers are not stupid or stubborn to complain about daylight savings time. Daylight savings time causes a phase shift in demand cycles, which disrupts the synchronization of supply and demand cycles established immediately prior to every change due to daylight savings time.
For those who haven't been keeping abreast of the debate, since daylight savings time was introduced decades ago, dairy farmers have been complaining about the problems it causes their cows.
Cecil, like many thoughtful people, has observed that what humans name an hour does not matter to a cow. On these grounds, he denies that dairy farmers have any legitimate reason to complain. Just milk the cows at the same time, regardless of whether it's labeled 5 a.m. or 6 a.m., and the cows won't have to adjust to being milked an hour later.
The flaw in this reasoning is that it does not take account of the relative timing between supply and demand. Suppose it is spring and the clock has moved an hour ahead, but the dairy farmer ignores the time change, and milks 24 hours after the last milking (not 23 hours after, as daylight savings would otherwise require). Now the cows are happy because they don't have to wake up earlier. But the distribution truck drivers are unhappy because like everybody else in the world they showed up an hour earlier, and now are late in delivering milk to the local supermarket. The same problem happens in reverse in the fall, when the truck shows up an hour after the milk has been sitting out, ready for pickup.
The only way for the farmer to avoid disturbing the cows is to convince the whole rest of the world not to pretend like it's an hour later in the spring and an hour earlier in the winter. Which is exactly what the farmers are trying to do.