Field Drivers, Hog Reeves and

It was the Field Drivers who turned out any cows or sheep found in a field of growing hay. They fined the owners of the  invading animals.
The Hog Reeves made sure that all the pigs had nose rings. Sticks were put through the rings to keep the pigs from getting through fences. The pigs ran freely everywhere. There must have been a great many pigs in Whitefield to have needed 14 Hog Reeves in 1810 ! (more likely it was the large size of our new town) .
Pound Keepers

Cattle pounds became a widespread feature of the hundred-year transition from exploring, hunting, and wood cutting to farming. When the isolated farm came to have near neighbors, pounds answered an urgent need for protection against stray animals. It is hard, today, to appreciate the impact of cattle grazing in a garden or in the wrong pasture. For families on subsistence farms, the winter's food for both humans and animals was at stake. Moreover, in certain seasons male animals on the loose created another difficulty: it was important for owners to be able to choose what male bred with what female.

Gardens were small and the return from fencing them was large, so gardens were fenced early, often by poles simply driven into the ground side-by-side. Pastures were larger; fencing them was difficult and expensive, so some were not fenced. Yet with near neighbors, cattle could easily stray from one pasture to another. At the earliest town meetings there were angry demands for an end to damage by marauding cattle. Towns may have hastened their incorporation partly because the election of pound keepers was apparently accepted as establishing a legal basis for impounding strays.

From the beginning several implicit concepts underlie the pound solution to the stray cattle problem: First, the owner was responsible for damage done by his animals; second, it was in the public interest that the person harmed or others should round up and drive offending animals to the pound ‑ originally the pound keeper's barn or farmyard; third, to get his animals back, the owner should pay for damage done. Later, two more concepts were added: the owner was to pay for the cost of feeding and caring for impounded animals, and fines were to be levied on the owner by the town. Eventually, the state legislature incorporated these and other sanctions.

When pound keeping in barns and in farmyards became too onerous, towns throughout the District or later the State of Maine authorized construction of one or more log pounds in strategic locations on land loaned for the purpose. No money was appropriated. Trees were there for the felling, and neighbors, no doubt, joined in the common effort, as they did for roads and barns. Later on, more prosperous voters would appropriate money to pay for the work. Then lob pounds were replaced by more secure and permanent stole structures. source