When the Vikings built their houses they made sure that there was a place inside to keep their animals as well.
These homes were known as longhouses, and there was an area at one end of it to store the animals.
Because it got colder and wetter in the countryside storing the animals inside meant that the farmer and their families and the animals would stay warmer and dryer if they all stayed under one roof.
The longhouses were not very good for the viking farmers health though, as they were made from wood and had grass roofs but no windows for ventilation.
So with all the smoke and dampness in these places vikings suffered badly from chest diseases.
Farmers were particularly fond of cows for they were a valuable asset to them. They gave milk and meat and clothes would be made from their skin. Also cow droppings were a great source of manure which helped the crops grow.