Pig slurry is classified as a natural fertilizer of animal origin, being a mixture of faeces, urine, remains of fodder and water used for the elimination of faeces. It is generated in non-bedding pig farming conditions, where animals are kept on slatted floors (grate or slotted floor). This paper presents the general characteristics of pig slurry, its physicochemical properties and its microbiological composition. Also, factors affecting slurry properties are discussed