Integrating swales into an area which will be fenced for rotational grazing changes the requirements for fencing in several ways. First let me define some terms. A Swale is a ditch on contour which is used to stop and soak water, stop erosion, and provide a uncompacted mound which is good for growing trees. Rotational grazing is an animal and land management strategy which attempts to maximize the productivity of a grazing scheme while regenerating and improving landscape, improve animal health by grazing an area once in a minimum of 21 days to break pest cycles and allow regenerative growth of forages, reducing or eliminating feed and fuel and labor inputs and the making of hay, and distributing urine and manure evenly throughout the system in a way that is beneficial to the land and animals.
In the picture below, I show the system I installed on the farm and have been moving pigs, chickens, turkeys, ducks, and rabbits through it. I wrote the word for each item in the color it is drawn in. As you can see, the swales have fencing on both sides to keep large animals from degrading the earthwork while allowing the smaller animals access to them. The birds are beneficial to the swales, they are too light to degrade them and they forage on and fertilize them. Fencing on both sides adds initial cost, labor, materials, length and complexity. It results in a system that day to day, is very user friendly and lays nice on the landscape because it follows the natural contours of the land. When the trees I planted on the swales are more mature, it will result in shade being distributed throughout my pastures, changing the species of grasses which can survive and providing shade to my animals and habitat for wild animals and insects.
In my setup, the animals have access at all times to a 110 gallon spring fed water tank, a simple rain shelter, a wooded loafing area near the water for shade, a 2 acre forest paddock rotated weekly, and the laneway which connects all the paddocks with one of the gates open and a new section of pasture daily. To clarify, I have one of the red gates open to one of the paddocks and after that I have a temporary fence with polyrope and step in posts run perpendicular to the paddock that I move 30-50' back daily. When I reach the end of a paddock (the side furthest from the red gate), I open the next paddock in the rotation and close off last one. I feed a small amount of grain, eggs, and molasses in the central area to keep them occupied while I move the fencing. I can get this "chore" done in 15 minutes and is all the pigs need in a day. I don't need to clean up poop, carry water, change bedding, and my animals are staying very healthy with no worming or vaccinations.
In late summer, I intend to leave some of the paddocks to grow to their full height and let them stand into the dormant season. I will then creep graze through this standing forage in the winter. I may not be able to have as many animals this way, but I won't need to buy or store hay, nor buy the expensive equipment and buildings and fuel and time and labor to make it and put it up. Not making or buying hay and holding to your winter carrying capacity increases the profitability of a farm according to modern grazers such as Jim Gerrish author of "Kick the Hay Habit" and "Management Intensive Grazing".
See the posted video for a better visual explanation. Enjoy!