Fermented total mixed rations (TMR) preparation technology enables the preparation of fermented feeds for livestock according to the nutritional requirements of ruminants, utilizing various agricultural by-product resources. This is important in reducing the cost of feed production, improving livestock productivity, and promoting sustainable livestock production. This chapter introduces the role played by the TMR center in effectively utilizing regional feed resources, preparation and storage, production and distribution, etc. It also introduces the role of TMR in maintaining the nutritional balance of livestock, promoting enterprise stability, expanding production scale, improving production environment, improving livestock feeding technology, and increasing farmers’ income. Introducing the TMR systems effectively enlarged the farm scale and shortened working time. It is necessary to understand that the chemical composition of by-products, self-produced silage, and imported hay included in TMR have wide varieties of chemical composition. Periodical monitoring of each TMR source is important to utilize the ingredients. The nutritional characteristics of typical food by-products, i.e., soybean curd residue, brewer’s grain, sake lees, winery grape pomace and sediment, noodle waste, and potato waste, as ingredients of TMR were discussed. Previous studies on the merits of feeding fermented TMR to lactating dairy cows and fattening beef cattle were proposed.