The historical facts about probiotics and practical importance of their use in animal nutrition described in this book. It provides material on the use of probiotics in modern pig farming and information on the effect of probiotics on the quality of pig production. There are also new data on the effect of probiotics on the digestibility of nutrients in the fodders for pigs, the microflora of the gastrointestinal tract and the morphological and immunological parameters of blood. In this monograph for the first time data on the effectiveness of the use of probiotics of different composition in mixed fodders for pigs in the conditions of the Republic of Moldova are presented. The monograph is intended for researchers and professionals in the field of animal nutrition.