An animal feeder comprising: a hopper defined by a bottom surface, opposed end walls, and opposed hopper walls; at least one trough defined by a bottom surface, opposed end walls, a trough wall, and a portion of at least one hopper wall; said trough being in communication with said hopper via an opening defined, at least in part, by said hopper wall; a gate sized to close the opening; said gate being movable to adjust the effective height of the opening; and an adjustment mechanism operable to adjust the vertical position of the gate (and hence the effective height of the opening); the adjustment mechanism comprising: a first cam and a second cam, each of said cams being mounted to said at least one hopper wall; the first and second cams being horizontally spaced apart from each other; a first link extending between and connecting said first cam to said gate and a second link extending between and connecting said second cam to said gate; a control rod extending between and connected to said first and second cams; characterized in that each of said cams (42,44) is rotatably mounted to said at least one hopper wall, said cams each being rotatable about a pivot axis; said first and second links being connected to said first and second cams (42, 44), respectively, at a point on said cams spaced from said pivot points of said cams, such that rotation of said cams is translated to vertical motion of said links; and said control rod being rotationally connected to said cams at points (42a, 44a) on said cams such said cams (42, 44) can rotate relative to said control rod and such that movement of said control rod in a direction of an axis of the control rod induces rotation of said cams (42, 44) about their pivot axes; at least said first cam being a control cam, said control cam comprising two or more position adjusting openings spaced from the pivot axis for said control cam; said control rod comprising a finger sized to engage a selected one of said adjustment position openings. a hopper defined by a bottom surface, opposed end walls, and opposed hopper walls; at least one trough defined by a bottom surface, opposed end walls, a trough wall, and a portion of at least one hopper wall; said trough being in communication with said hopper via an opening defined, at least in part, by said hopper wall; a gate sized to close the opening; said gate being movable to adjust the effective height of the opening; and an adjustment mechanism operable to adjust the vertical position of the gate (and hence the effective height of the opening); the adjustment mechanism comprising: a first cam and a second cam, each of said cams being mounted to said at least one hopper wall; the first and second cams being horizontally spaced apart from each other; a first link extending between and connecting said first cam to said gate and a second link extending between and connecting said second cam to said gate; a control rod extending between and connected to said first and second cams; a first cam and a second cam, each of said cams being mounted to said at least one hopper wall; the first and second cams being horizontally spaced apart from each other; a first link extending between and connecting said first cam to said gate and a second link extending between and connecting said second cam to said gate; a control rod extending between and connected to said first and second cams; characterized in that each of said cams (42,44) is rotatably mounted to said at least one hopper wall, said cams each being rotatable about a pivot axis; said first and second links being connected to said first and second cams (42, 44), respectively, at a point on said cams spaced from said pivot points of said cams, such that rotation of said cams is translated to vertical motion of said links; and said control rod being rotationally connected to said cams at points (42a, 44a) on said cams such said cams (42, 44) can rotate relative to said control rod and such that movement of said control rod in a direction of an axis of the control rod induces rotation of said cams (42, 44) about their pivot axes; at least said first cam being a control cam, said control cam comprising two or more position adjusting openings spaced from the pivot axis for said control cam; said control rod comprising a finger sized to engage a selected one of said adjustment position openings.