Mokushi was a govermental post in the Edo period which was in charge of maintaining ranches under direct control of the bakufu, as subordinates of an officer in the bakufu, and it is said that the officers in the post were responsible for managing the Goyoboku of the Tokugawa bakufu (public ranches of horses + hunting grounds for Shogun).
牧士（もくし）とは江戸時代、幕府の役人の配下として、幕府直轄の牧場の維持管理を担った一つの役職のことを言い、徳川幕府の御用牧（公営馬牧場＋将軍の狩猟場）の管理を任されていたとされる。