Abstract: A structural element (2), suitable for use in the manufacture of a release device for intraruminal administration of an active agent to a ruminant animal, is of a compacted material, which material comprises a mixture of powdered iron, graphite and optionally copper, the graphite being present in the mixture in an amount of from 2 to 7 wt %, the copper in an amount of from 0 to 5 wt % and the iron in an amount of from 88 to 98 wt %, by weight of the total weight of iron, copper and graphite. A plurality of structural elements (2) may be assembled to provide a structural unit (4) of a release device.

Abstract: The invention provides a magnesium manganese alloy suitable for use in the production of a pellet 10 for administration to a ruminant by dposition in its rumenoreticular sac. A typical pellet 10 comprises a magnesium alloy tube 12 enclosing a degradable core formed of plurality of tablets 14, 16. The magnesium alloy used in the construction comprises at least 90% by weight of magnesium, uyp to 1% zinc and up to 2% of manganese. Preferably the alloy may further include aluminium, silicon or zirconium along with iron and beryllium. When deposited in an animal's rumen the alloy reacts with the rumen juices to form an anodic film over the exposed surface of the tube 12. This prevents corrosion or dissolution of the tube 12 except at its exposed ends where galvanic corrosion by coupling with the electrically conductive core 14, 16 is provided. The normal requirement of a non-degradable exterior coating e.g. resin for the tube exterior is obviated.

Abstract: A pellet for administration to ruminants to supply magnesium and other biologically active material, for example, anthelmintics or antibiotics comprises a tube of magnesium alloy 1 enclosing a core or filling 3. The core 3 typically comprises mainly iron shot as weighting material, a biologically active material if desired and an electrically conductive material such as carbon or graphite. The graphite ensures that the core 3 as a whole is conductive and provides a cathode electrically coupled with the magnesium alloy tube 1 to form a galvanic cell. Liquor in the rumen serves as an electrolyte to cause galvanic corrosion of the magnesium tube 1 to release the active material contained in the core 3. A protective coating 5 of resin is provided on the tube's exterior surface except on at least one end 4 so that the corrosion is limited to the exposed surfaces only. An alternative embodiment (FIG.

Abstract: A bolus for administering a biologically active material for example an insecticide into a liquid environment such as the water of a reservoir or lake or an anthelmintic into the rumen juices of an animal comprises a succession of liquid impermeable outer segments (153, 263) enclosing a core which in the simplest case may be a single unitary active material segment (151, FIG. 14) or in a developed embodiment may comprise a succession of annular segments (269, FIG. 25) contained in sealed recesses (267) in the outer segments (263) which are located on a degradable central rod (265) e.g. of magnesium alloy, which itself will be active for instance to combat magnesium deficiency.As shown in FIG. 25, the device may incorporate a weight (275) which, in animal use, inhibits regurgitation.

Abstract: A pellet for administration into and reside in the rumeno-reticular sac of a ruminant and to release successive doses of an active agent, such as an anthelmentic, comprises an assembly (10) of discs (12) each having a peripheral skirt (14) on one side and an inwardly-spaced skirt (16) on the other so that such discs can interfit by said skirts (14, 16) and define therebetween cavities (18) each containing a respective active agent dose (24). A weighting slug (20) is provided at one end of the assembly (10) which is enclosed except at one end by a surrounding plastics sheath (26) so that rumen juices may attack and erode the successive discs (12) to release the successive doses (24). The discs (12) are of a magnesium-based alloy and the slug (20) is of a Zinc-based alloy.