GB2099699A - Device for introducing nutrients and/or therapeutic materials into ruminant animals - Google Patents

Description

SPECIFICATION Device for introducing nutrients and/or therapeutic materials into ruminant animals The subject of this invention is a device for the easy introduction of nutrients and/or therapeutic materials into ruminant animals. In particular it is concerned with the development of a heavy pellet of such characteristics that it can be swallowed after oral administration and remains to dissolve slowly in the rumeno-reticular sac so that it is neither lost by regurgitation nor by passage in the faeces. The advantage of using such a sustained release device is to avoid the frequent handling or gathering of livestock at regular intervals. Under some extensive grazing situations it may be the only practical means of administration. Such devices for introducing nutrients and therapeutic materials into animals are known. One such customary device is of a cylindrical shape and contains the desired nutrients and/or therapeutic materials. When swallowed by an animal it releases in the animals's rumenoreticular sac the nutrients and/or therapeutic materials contained therein. It has heretofore been difficult in the use of such devices to ensure that the rate of release of material lies within a chosen range because as the device dissolves away the area exposed to the rumen liquor of the animal usually changes. Certain substances which are essential nutrients or therapeutic materials can cause harm or be ineffective for an extended period if released at too great a rate and of course have little or no effect if released at too low a rate.Examples of nutrient substances which it is often found desirable to introduce into ruminant animals are vitamins A, D and E and trace elements such as copper and cobalt. Examples of therapeutic substances are anthelmintics and growth-promoting substances. The various known forms of heavy pellet include a cobalt bullet which is a baked ceramic cylinder having a cobalt salt as an ingredient and having an integral density of 4 without the. need for any further weighting device. The cobalt leaches out over a period of time into the rumen of the animal but this design of pellet tends to coat over with a deposit of insoluble calcium phosphate and other salts which prevents any further cobalt dissolution. Another example is a magnesium pellet containing metallic magnesium. Small iron shot particles are included to increase the overall pellet density. These are ultimately excreted via the faeces. Whereas it can successfully supply magnesium, its design can only be applied to the supply of elements which can form suitable metal alloys. Another known form of device consists of active material enclosed within a stainless steel tubular casing closed at the ends by permeable diaphragms. As such a casing is normally about 2.5 cms in diameter and about 10 cms long, the insoluble residue i.e. the steel casing, left by the use of one such device is quite considerable. As i the overall specific gravity of the residue is high and above the critical value, the animal cannot expel it. Repeated dosing of the same animal would lead to an increasing number of residual shells retain in the reticulum. Other known forms of rumen devices include contraptions which extend spring-loaded arms after administration in order to prevent dislodgement of the device from the reticulorumen. Such mechanical devices leave considerable metallic residues and incur high manufacturing and retail costs. These examples illustrate some of the problems associated with the design of a rumen pellet. The two main objectives are to ensure a steady release of the nutrient or therapeutic substance over a chosen length of time and to ensure that the density is sufficiently high to prevent injection of the pellet. This in most cases entails the inclusion of some inert heavy material such as iron, preferably in a form which will be excreted by the animal after it has served its function as a weighting device. It is an object of the present invention to provide a device which does not suffer from the described disadvantages associated with the known devices. According to the invention a device for introducing at least one substance of a nutrient and/or therapeutic nature into a ruminant animal comprises an elongated pellet incorporating a core the constituents of which include at least one active substance in the form of compressed particles and a flexible casing enclosing the core formed of a substance which is insoluble in the rumen liquor of the animal and which is in a state of hoop stress so that without the support provided by the core it would contract circumferentially. The core may also incorporate at least one inactive substance of high specific gravity preferably also in the form of particles. The device may be rendered capable of supplying doses of the active substance at chosen intervals of time by incorporating in the core strata of soluble inactive material spaced at distances along the core such as to provide inactive periods of the device while the inactive material is dissolving. The pellet may be of constant cross-sectional area through its length or may vary in cross section, for example it may be coned, so that the rate of release of the active substance may be caused to vary. The casing may be of latex rubber applied in such a way that it is under a hoop stress. This may be done by fitting the core into a preformed tube of latex rubber of cross-sectional dimensions smaller than the cross-sectional dimensions of the core, the ends of the tube being closed so.that normally the core is completely encased and protected from outside contamination. Alternatively the rubber may be applied in a liquid state by dipping or spraying in such a manner as to cause the coating when set to exhibit a hoop stress and yet be capable of further expansion without cracking or splitting since the pellet may swell in contact with the fluid medium. Alternatively the casing may be formed of an insoluble plastics material applied by spraying the core with or dipping the core into the plastics material while it is dissolved in a volatile solvent, evaporation of the solvent causing the material to become set and be subjected to a hoop stress as it tries to shrink. Alternatively the core may be dipped into a liquid plastics material which is subsequently set by the catalyzing action of a chemical agent or by exposing it to radiation by heat or light, the material trying to shrink as it sets. The action of dipping or spraying causes the core to be covered completely so that no separate action requires to be taken to seal the core within the casing. The material of high specific gravity may be particles of iron or any other metal or salt of a metal of sufficiently high specific gravity to impart to the device a chosen minimum specific gravity usually greater than 2.0, which is about the minimum specific gravity required of any appropriately shaped article which the animal is to retain in its rumen or reticulum. The preferred density is generally in excess of 2.5. The pellet may be made sufficiently rigid for handling purposes by making the particle size of the powders constituting the elements of the pellet of sufficiently small size and compacting them by compressive force. With certain materials cohesion of the particles may be assisted by including a binder preferably of a material harmless to the animal such as starch. A practical embodiment of the invention is illustrated in the accompanying drawings in which Fig. 1 illustrates in longitudinal section a device in its sealed state, Fig. 2 illustrates in longitudinal section a device the core of which has been partly dissolved and Fig. 3 illustrates in longitudinal section a device arranged to provide a rising or falling rate of release of the active substance according to which end is initially opened. In the drawings 1 denotes a core formed of particles of active material and particles of material inert to the animal and of a high overall specific gravity and 2 denotes a casing of elastic material in a state in which it is subjected to a hoop stress. The lines 3A and 3B indicate alternative positions where the device may be sectioned before administration to the animal to expose one end of the core 1. Referring to Fig. 2 it will be seen that the casing 2 at the point where the core has dissolved has shrunk as at 4 and constricted the area of entry of the exposed end face 5 of the core 1. The end portion 6 presenting the end face 5 has swollen slightly but this has been accommodated by an expansion of the elastic casing at this point. In practice a device is used by cutting the device at 3A or 3B to expose an end face 5 of the core 1 and then causing the animal to be treated to swallow the device. The rumen liquor of the animal acting on the exposed end face of the core causes the core to start to dissolve releasing the required material into the rumen or reticulum of the animal. The particles imparting the high specific gravity of the device are released also but either dissolve, or if insoluble pass through the animal without effect. Since the proportion of the constituent of high specific gravity to the active constituents does not change significantly during the entire active life of the device the overall specific gravity of the device remains substantially constant. Since the casing is a thin tube of light material although it contributes a constant weight to the overall weight of the device that constant is so small that it has little affect on the overall specific gravity as the core is used. As the core approaches exhaustion and becomes exhausted the overall specific gravity of the residue of the device drops to the specific gravity of the casing and thus becomes well below the critical specific gravity for retention by the animal. The animal then automatically expels the empty casing. While the device is being subjected to the rumen liquor, the open part of the exposed surface becomes impregnated to some extent and may swell. This has two effects. It distends the casing and the casing being flexible gives way without disruption. At the same time in distending its hoop stress increases. Swelling of the core would normally cause an increased dissolution of the core material in a given time. This is however counteracted by the fact that as core material is dissolved the support of the core material for the outer casing is withdrawn and because of the hoop stresses in the casing the casing contracts and reduces the area of access to the core to approximately the area of access originally presented so that the rate of movement of the active material into the rumen or reticulum of the animal remains substantially constant.

Claims (12)

1. A device for introducing at least one substance of a nutrient and/or therapeutic nature into a ruminant animal comprising an elongated pellet incorporating a core the constituents of which include at least one active substance in the form of compressed particles and a flexible casing enclosing the core formed of a substance which is insoluble in the rumen liquor of the animal and which is in a state of hoop stress so that without the support provided by the core it would contract circumferentially.

2. A device as claimed in claim 1, in which the core also incorporates at least one inactive substance of high specific gravity.

3. A device as claimed in claim 1 in which the core incorporates strata of soluble inactive material spaced at distances along the core.

4. A device as claimed in claim 1, in which the pellet varies in cross-sectional area throughout its length.

5. A device as claimed in claim 1 in which the casing is of latex rubber applied in such a way that it is under a hoop stress.

6. A method of forming the device as claimed in claim 1 in which the core is fitted into a preformed tube of latex rubber of cross-sectional dimensions smaller than the cross-sectional dimensions of the core and the ends of the tube are then closed so that the core is completely encased and protected from outside contamination.

7. A method of forming the device as claimed in claim 1 in which latex rubber is applied to the core in a liquid state in such a manner as to cause the coating when set to exhibit a hoop stress and yet be capable of further expansion without cracking or splitting.

8. A method of making the device as claimed in claim 1 in which the core is coated with insoluble plastics material while the plastics material is dissolved in a volatile solvent, then evaporating the solvent.

9. A method of making the device as claimed in claim 1 in which the core is dipped into a liquid plastics material which is then set by the catalyzing action of a chemical agent so that setting is accompanied by a tendency to shrinkage.

10. A method of making the device as claimed in claim 1 in which the core is dipped into a liquid plastics material which is then set by exposing it to radiation so that setting is accompanied by a tendency to shrinkage.

11. A device as claimed in claim 1 in which the material of high specific gravity is of a specific gravity high enough to impart to the device a chosen minimum specific gravity greater than 2.0.

12. A device for introducing nutrients and/or therapeutic materials into ruminant animals substantially as described with reference to the accompanying drawings.