Before the advent of artificial fertilizers, distant pastures on many mixed Farms would be inaccessible the to the large farm manure wagons bringing manure from the Farm yard. These would have had a visit from the Shepherd and his flock of Sheep. The Sheep were not allowed to wander freely but were kept enclosed behind wooden hurdles. This process was called ‘folding’. Once the forage crop had been grazed, the Sheep, Shepherd, his dog and mobile home; his Shepherds Hut, would move to pastures new. The land would then be ploughed, returning the nutrients in the droppings to the land. The Hut contained a small stove, a straw bed over a cage where lambs could be kept (known as a Lamb rack) and a simple medicine cupboard containing various potions. This regularly included a bottle of Whisky to revive a sickly lamb (or Shepherd).
You can find other great example of Shepherds huts over at readersheds.co.uk