I had to go digging to find it for here, have never heard anything about fence laws here in my day to day life ever. Nothing much specific about it anyways.
Fences
5 (1) The owner of a livestock farm shall build and maintain fences adequate to prevent his livestock from escaping from his farm.
2) The owner of a non-livestock farm adjoining a livestock farm shall not plant or cultivate any crop other than hay or pasture that would constitute an enticement to livestock closer than eight feet to a fence built or maintained pursuant to subsection (1).
(3) When a livestock farm adjoins another livestock farm, the owners of those farms shall share in the costs of building and maintaining common fences in such proportions as may be agreed upon between them and, failing such agreement, in such proportions as the committee for the municipality in which the lands are situated shall determine pursuant to this Act.
(4) Subsection (3) shall not apply when one of the farms has been operated continuously as a non-livestock farm for a period of one year. R.S., c. 166, s. 5.