N.J. Stat. § 4:20-2: Sufficiency of partition fences

A fence set in the line of partition between persons either of whom shall improve his adjoining lands shall, in addition to compliance with section 4:20-1 of this title, be so close, strong and sufficient as to prevent sheep from going through or under it, except that owners of adjoining lands lying upon streams or rivers subject to overflow, commonly known as lowland meadow, shall be exempt from fencing against sheep unless by mutual agreement.