A feeder for dispensing feed to livestock, comprising: - a hopper comprising a sidewall and a bottom; - a mechanical rotary feed flow system having a central feed discharge hole that extends through the bottom of said hopper and an animal-activated sweep member for sweeping feed from said hopper into said central feed discharge hole for discharge from said hopper; - said mechanical rotary feed flow system comprises a deflector mounted in said hopper above said hopper bottom and vertically spaced from said hopper bottom, said deflector covering said central feed discharge hole to restrict gravity flow of feed from said hopper through said central feed discharge hole, said sweep member being mounted for rotation about a vertical axis, and said sweep member being located between said deflector and said hopper bottom for sweeping feed to said central feed discharge hole to discharge therethrough; - said sweep member is operably coupled with a feed wheel disposed in a trough below said hopper so that animal-induced rotation of said feed wheel in said trough causes rotation of said sweep member in said hopper for sweeping feed to said central feed discharge hole for discharge into said trough; characterized by: - said feeder having a gravity flow feed system in addition to said mechanical rotary feed flow system, said gravity flow feed system having at least one gravity flow feed opening that extends through said hopper bottom for allowing feed to flow by gravity from said hopper, said gravity flow feed opening being separate from said central feed discharge hole, and said gravity flow feed opening being located between said central feed discharge hole and the sidewall of said hopper; - a closure system associated with said gravity flow feed system, said closure system having a first condition in which said gravity flow feed opening is open to allow gravity feed flow through said gravity flow feed opening, and a second condition in which said gravity flow feed opening is closed; and - an activator mechanism associated with said feed wheel that is arranged to cause said closure system to change from its first condition into its second condition upon rotation of said feed wheel. - a hopper comprising a sidewall and a bottom; - a mechanical rotary feed flow system having a central feed discharge hole that extends through the bottom of said hopper and an animal-activated sweep member for sweeping feed from said hopper into said central feed discharge hole for discharge from said hopper; - said mechanical rotary feed flow system comprises a deflector mounted in said hopper above said hopper bottom and vertically spaced from said hopper bottom, said deflector covering said central feed discharge hole to restrict gravity flow of feed from said hopper through said central feed discharge hole, said sweep member being mounted for rotation about a vertical axis, and said sweep member being located between said deflector and said hopper bottom for sweeping feed to said central feed discharge hole to discharge therethrough; - said sweep member is operably coupled with a feed wheel disposed in a trough below said hopper so that animal-induced rotation of said feed wheel in said trough causes rotation of said sweep member in said hopper for sweeping feed to said central feed discharge hole for discharge into said trough; - said feeder having a gravity flow feed system in addition to said mechanical rotary feed flow system, said gravity flow feed system having at least one gravity flow feed opening that extends through said hopper bottom for allowing feed to flow by gravity from said hopper, said gravity flow feed opening being separate from said central feed discharge hole, and said gravity flow feed opening being located between said central feed discharge hole and the sidewall of said hopper; - a closure system associated with said gravity flow feed system, said closure system having a first condition in which said gravity flow feed opening is open to allow gravity feed flow through said gravity flow feed opening, and a second condition in which said gravity flow feed opening is closed; and - an activator mechanism associated with said feed wheel that is arranged to cause said closure system to change from its first condition into its second condition upon rotation of said feed wheel.