Abstract: Alimentary and/or medicinal active principles intended for feeding or treating ruminants are polished by spraying a solution of one or more active principles, resins and/or sugars onto the said active principles. The polished active principles are then coated with a polymer providing protection in the rumen.

Abstract: A composition which is stable in a medium in which the pH is greater than or equal to 5.5 and which permits the release of an active substance in a medium in which the pH is less than or equal to 3.5, comprising the active substance, which contains inclusions of, or which is completely or partially covered by, a pH sensitive material whose extent and/or rate of swelling is greater in an acidic medium than in a neutral medium, and a coating of a hydrophobic layer.

Abstract: A composition for coating a biologically active substance, which is stable in a medium with a pH greater than or equal to 5 and which enables the active substance to be released in a medium with a pH less than or equal to 3.5, consisting of a basic amino copolymer (preferably vinyl-pyridine/styrene copolymer) and a hydrophobic substance with a melting point greater than 60.degree. C. (preferably stearic acid), the hydrophobic substance content being between 50 and 90% of the total mass of the coating, and granules comprising a nucleous containing the biologically active substance, coated with this composition.

Abstract: A composition for coating a biologically active substance which is stable in a medium in which the pH is greater than or equal to 5 and which permits the release of the active substance in a medium in which the pH is less than or equal to 3.5, comprises a film-forming, water-insoluble binder which possesses controlled hydrophilicity and is optionally slightly sensitive to pH variations, and a substance which is sensitive to pH variations (e.g. an inorganic filler, simple aminated substance, basic polymer or copolymer, chitosan). Pellets for feeding to ruminants consist of a core containing the biologically active substance, e.g. methionine or lysine, coated with this substance.

Abstract: Composition for feeding ruminants, containing a water-soluble biologically active substance which is stable in a medium whose pH is greater than or equal to 5 and which permits the release of the active substance in a medium whose pH is less than 3.5, comprising:a core containing the active substance, which has optionally undergone a surface treatment,a first coating layer consisting of a film-forming substance sensitive to pH variations, optionally in combination with an inorganic filler, anda second coating layer consisting of a hydrophobic substance, optionally in combination with an inorganic filler.

Abstract: Composition for coating a biologically active substance, which is stable in a medium of which the pH is greater than or equal to 5, and which permits the release of the active substance in a medium of which the pH is less than or equal to 3.5, and biologically active substances when surrounded by this composition.