The group said pro-hunt campaigners would demonstrate at every stage of the Bill - which outlaws stag hunting and harecoursing and restricts fox hunting.
Mr Gilbert admitted that harecoursing remained a big problem and urged anyone affected by it to report the crime to police "with as much detail as possible".
Before the debate, the DUP's Jim Wells questioned the necessity of discussing the amendment brought by Sinn Fein's Francie Molloy to allow two "regulated" harecoursing events to be maintained in Northern Ireland.
Hard-line opponents of hunting accept that such a formula, combined with a ban on harecoursing and stag hunting, may be acceptable to many Labour MPs who have so far voted consistently for an outright ban.
But while the amendment introducing a permanent ban on coursing was carried, there was relief for beagle and harrier packs as a more stringent hare protection measure was dropped.