Abstract: A composition comprising the dry extract of ruminal content of bovine and sheep and the caecal content of rabbit is described which can be used as a powdered dietary supplement for pets and farm animals as it retains intact the nutritional components of the starting material, such as volatile fatty acids, amino acids, vitamins, minerals and dietary fibres, but it also contains a very high load of bacterial derivatives, protozoa and yeasts, which are able to stimulate the immune system of the gastrointestinal tract; and the process for preparing it.