A method and system for supplying increased bio-available quantities of amino acids or chemical derivatives in liquid form to ruminant livestock. The method includes supplying a liquid, supplying at least one amino acid, producing a liquid mixture by mixing the liquid with the amino acid(s), and administering the liquid mixture to ruminant livestock drink supply in a controlled manner. The system of the present invention may include a fluid supply line (2), a one-way valve (1) connected to the line (2), a measurement device (3) connected to the line (2) downstream from the one-way valve (1), a pump (5) for injecting amino acids into the fluid system, and containers (9, 9') for retaining the amino acids which are drawn up by appropriate devices (11, 11') and are introduced into the flow of liquid towards drinking troughs (7).