Shires has been involved in eventing for three years with the Wales and West Eventers League and will now support British Eventing's largest competitor base, Pre-Novice championship, with over 200,000 cross country rounds at this level this season.
The event has only been running for two years and involves around 2000 riders who are eligible to compete in one of 12 regional finals in a bid to reach the championship.
Qualification began in June and the championship will take place at the Grassroots Festival at Aston-le-Walls in Northamptonshire in August 2008.
Marcus Cridland, marketing director at Shires Equestrian, said: "We feel that supporting horses and riders at this level is essential to the success of what has to be one of the most demanding equestrian sports."
Mike Etherington-Smith, sport director at British Eventing, said: "The amateur side of the sport is vital to our continued success and it is tremendous that one of Britain's leading equine suppliers is supporting this level."