Around 8,000 farmers and supporters have taken part in a demonstration in Dublin organised by the Irish Farmers' Association.
The rally was in protest at an investigation by the Competition Authority into possible price-fixing in the milk market, which culminated in a raid on its offices in recent weeks.
The Authority has said it acted in the public interest.
The protestors marched to the Department of Agriculture on Kildare Street. Some of them were on tractors, but the majority were on foot.
In a statement, the Competition Authority said that it did not normally comment on its investigations, but that in view of recent statements by the IFA, the Competition Authority believed that was in the public interest to issue a brief statement.
The Competition Authority said the search of the IFA headquarters was part of an ongoing investigation into possible price-fixing in the liquid milk market.
It said the search followed recent incidents involving the disruption by groups of farmers of normal business at a number of retail outlets.
The search was carried out in a highly professional manner by experienced members of the Authority's investigative staff, the Competition Authority said, including a Detective Sergeant who is on full-time secondment to the Authority from the Garda Bureau of Fraud Investigation.
The Department of Jobs, Enterprise and Innovation said Mr Bruton had not refused to meet the IFA.
In a statement, the Department said that IFA had requested two meetings with the Minister in recent weeks, one of which was to discuss the Competition Authority investigation.
The Department said as the Competition Authority was an independent statutory body, it would not be appropriate to discuss an ongoing investigation by it.