CHICAGO, May 14 (Reuters) - U.S. cattle producers have

started rebuilding the nation's herd or are close to doing so,

Tyson Foods ( TSN ) CEO Donnie King said at an investor event on

Wednesday, after supplies dwindled to their lowest level in

decades.

Producers increasingly sent cattle to slaughter, instead of

keeping them to reproduce, in recent years as drought reduced

pasture lands available for grazing.