From what I understand of Holzer, his setup is similar to ours. Not surprising as similar climate creates convergence of methods. Thus I might be able to give you some insight:
To find out his climate and precipitation look it up for his area. Keep in mind there may be micro-climate differences. This is especially true for people who live in mountains like we do. Typically Spring comes a month earlier down in the valley than it does for us. Winter comes a month earlier as well.
A photo of his place that I saw in an article looks remarkably like ours. Winters are cold and deep, summers are warm and moist but not hot or dry. Our summer is typically in the 60's to 70's with a high of 86°F (maximum in last 25 years) and our winter temps are typically in the -10°F to +10°F range with lows often of -25°F with occasional dips to -45°F. Lots of wind. Because of our location on the lee of the mountains we get more precipitation than other areas around us as the rain and snow both dump here. A lot of our precipitation comes in the winter as snow, about 14' a year that packs to about 4'. Lots of wind as we're both high up in the mountains.
We graze about 400 pigs on pasture using managed rotational grazing. The size of the paddocks vary greatly. Some are several acres, some are a quarter acre. The size depends on the use, that is to say what age groups of pigs, as well as terrain and geography. If I use a small paddock with a large group or large grazers then I move them through faster. With smaller grazers or a smaller group I'll move them more slowly. A good way to look at it is how many pounds of animal are on the paddock rather than how many animals.
Don't use time or dates for livestock moving-out of a paddock but rather use forage height. They should mow down a paddock in three days to a week, never more than three weeks because you don't want them picking up parasites from eggs they've dropped. A big part of managed rotational grazing is breaking the parasite life cycles naturally. The move-in time is a minimum of three weeks with a month or longer being better. How you size the paddocks is going to depend on how many animals of what size you have and how fast your forages grow.
Another factor is what are you trying to accomplish. Sometimes I'm renovating what used to be forest, sometimes I'm grazing developed pasture, sometimes I'm tilling up a garden, sometimes I'm killing down weed species I want to get rid of and then hand broadcast seeding behind the animals.. All of these require different management. If you want to till or kill you mob-graze intensely.
An example of density is this week we had about 100 roaster to finisher pigs on one pasture that was about three acres for about a week. This was new pasture we were reclaiming for forest. After they had been on it for most of the week I broadcast seed while they were still stirring it up. Two days later I moved them to the next paddock and it rained which sprouted the seed. This sort of timing with the weather helps avoid the need for mechanical seeding (tractor) which is important on our steep slopes. Some of our land we have terraced but the majority is sloping mountainside that one would not want to drive a wheeled vehicle on, or more likely roll downward. This is why grazing livestock works so well in the mountains.
We fence primarily with high-tensile smooth wire electric around the outside perimeter and then mostly polywire on step-in posts for paddock divisions. Typically one to two wires at low and walking nose height. Mostly we don't fence for piglets, they follow the herds. We have livestock guardian herding dogs for moving the pigs, retrieving escapees and eating predators. We also use some woven wire, some netting and some stock panels.
The pasture season runs about April (warm year) or May (most years) through October or November (warm year). During the winter the animals are up on top of snow pack and have open sheds with deep beds of composting wood chips & hay. For their diet, we replace summer's pasture with winter hay. Hay is not as good as pasture but it is better than nothing. On days like to day (-7°F, high winds) one pretty much hunkers down and waits.
In the fields we plant turnips, kale, rape, legumes (alfalfa, clovers, etc) as well as grasses, grains, millet, etc. We have fruit trees which provide fall food. There are also nut trees. We plant pumpkins, beets, turnips, radishes, squash, sunchokes, sunflowers and such in the winter paddocks which provide fall and early winter food - unfortunately this never lasts until spring. We don't buy or feed commercial hog feed/grain. We do get a small amount of spent barley from a local brew pub. Look around for resources in your area for things like that.
See:
http://www.google.com/search?q=site:sugarmtnfarm.com+managed%20rotational%20grazing
http://sugarmtnfarm.com/2006/05/15/of-tiller-pigs-weeder-chickens/
http://sugarmtnfarm.com/2010/09/15/frost-seeding/
Every location will be different with varying resources, climate, etc. The key is to adapt to what you have rather than trying to mimic someone else's methods. What others do is merely a jumping off point, a small guide.
Cheers,
-Walter
Sugar Mountain Farm
in Vermont