Nutrition product, particularly for breeding animals and for soils, characterized in that it is comprised of aggregates of organic sea limestones of recent formation, particularly shells, more particularly oysters, or lithothamnion algae, of which one portion is in the form of at least one of the mono-, bi- and tricalcic phosphates resulting from the action of phosphoric acid on said sea limestones. The product is made in an installation comprising a horizontal cylindrical reactor (1), a rotor (3) comprising means (5, 7) for mixing the aggregates, heating means (13, 18), means (15) for the supply of aggregates, means (16, 17) for the supply of at least the phosphoric acid, means (28) for discharging the treated aggregates and means (19) for sucking the gas elements resulting from the reaction.