To provide a rearing method that improves quality of a product such as egg, meat, etc., and can improve the feed demand ratio, etc., while maintaining a hygienic rearing environment.

A method for rearing chicken or pig of livestock includes continuously feeding a feed mixed with collagen and vitamin C to the livestock for seven days or more so as to increase the amount of hydroxyproline contained in at least thigh meat in the meat of the livestock. When the livestock is chicken, the thickness of shell membrane of egg laid by the chicken is thickened. Further electrolyzed water having disinfecting power obtained by electrolyzing a saline solution containing a small amount of salt is taken as drinking water in the livestock for the period. The method is similarly applied even to rearing facilities.