Teagasc lists info on Bolus RFID Tags
Electronic Animal Identification
Rumen boluses
Background
Implantable electronic transponders offer a reliable, tamper proof system of individual animal identification (Lambooij 1991, Konerman 1991, Pirklemann et al. 1991). The outcome from a number of studies (Fallon and Rogers 1992, Hasker et al. 1992, Conill et al. 1996) indicated that injectable transponders placed in the ear beneath the scutellar cartilage (C site) achieved the lowest failure rates. Implantation at the C site in a number of studies gave 100% retention and reading rate (Fallon and Rogers 1999). However, this site had one very serious disadvantage: recovery at slaughter was unpredictable. In calves implanted at 1 to 2 months of age, 35/112 transponders (31%) remained in the head when the ear was removed post slaughter at 22 months of age (Caja et al., 1997). Similar results were obtained in an English and in a German study with calves (A. Sains, personal communication). Due to the possibility of a transponder which could not be recovered at slaughter subsequently entering the food chain, it was considered impractical and unwise to proceed with an animal identification system based on transponders implanted subcutaneously or intramuscularly. Hanton (1981) showed that it was possible to electronically identify cattle using an active (internal power source) rumen electronic transponder which was administered via the oral route. Hanton's bolus was approximately 8cm long and 1.5cm in diameter. It had a specific density of 2.0 and was administered to the animal with a bolus gun similar to that commonly used for cattle. This bolus was successfully administered orally to newborn calves in the first 3 days of life.
Rumen boluses development
Rumen boluses have been used as vehicles to deliver various products directly into the rumen on a slow release basis (Allen et al. 1983). The products included trace elements, growth promoters, anthelmintics and antibiotics. This development of the rumen boluses used to electronically identify cattle incorporated the previous knowledge gained from the use of such therapeutic boluses in the rumen.
Rumen bolus - trace elements: Soluble-glass boluses administered selenium (Se) intraruminally, by balling gun, have been used to increase whole blood glutathione peroxidase concentrations in cattle (Hemingway 1999, Henry et al. 1995, Hidiroglou et al.1987, Maas et al. 1994 and Millar et al. 1988). Similarly copper (Cu) was administered to ruminants using sustained-release rumen boluses (Allen et al. 1986, Givens et al. 1988 and Parkins et al. 1994). Cylindrical rumen boluses (55mm length x 18 mm diameter with a density of 2.9 g cm3) suitable for ruminating calves over 75 kg liveweight were used to supply trace elements and vitamin (Hemingway et al. 1997). Investigations in Edinburgh used a soluble glass bolus to provide a slow release of Cu or cobalt (Co) into the rumen (Allen et al. 1986). Other studies have investigated the acid base reaction of cements in the construction of rumen boluses used to supply Cu, Co and Se (Manston et al. 1985).
Rumen bolus - growth promotors: Capsules (boluses) were used to provide slow release of an ionophoer, monensin, used to modify rumen fermentation (Micol et al. 1987, Tudor et al. 1980 and Watson and Laby 1978). The monensin capsule consisted of a metal cylinder within which was a matrix containing the monensin. A spring driver plunger pushed the matrix through an orifice (Watson and Laby 1978). The total core length was approximately 11 cm. The rate of plunger travel was independent of the concentration of monensin in the matrix over the range examined (12.5 to 50.0%). Thus, by choosing the appropriate combination of orifice size and matrix composition, the capsule can be designed to reliably release monensin at a given rate for a predetermined period so as to obtain maximum advantage from the use of the drug. The monensin delivery device was also described as a core assembled into a metal cylinder and secured by means of an adhesive filling the annular space between the matrix core and the interior wall of the cylinder. Either plastic snap-on end-caps with perforations or a plastic shell with perforated ends were applied to the metal cylinder to provide protection to the exposed flat faces of the cylindrical core matrix (Watson and Laby 1978).
Rumen bolus - dispensors: A slow release rumen capsule or bolus containing pluronics was used to control bloat in grazing cattle (Langlands and Holmes 1975). A sustained-release rumen bolus containing tetrachlovinphos was used against musca autamnalis (Riner et al. 1981).
A study (Riner et al. 1982) was conducted to determine the relationship between density of the bolus and location in the forestomachs and the influence of these factors on bolus erosion. Boluses with densities of 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, and 2.4 g/cm3 were produced from inert materials and administered to 6 fistulated Hereford heifers. A minimum density of 1.6 g/cm3 was required to prevent regurgitation from the ruminoreticulum and a minimum of 2.0 g/cm3 required for retention in the reticulum.
Boluses containing hexacyanoferrates were developed to effectively bind radioactive caesium thereby preventing its uptake by animal tissue in cattle grazing pasture after the Chernobyl accident (Hove 1993, Ratniknov et al. 1998).
Electronic rumen bolus
Previous studies have shown that an injectable transponder at the ear base site in cattle was a reliable method of animal identification. However with the injectable transponder it was possible that it might not be removed at slaughter and could therefore enter the food chain (Fallon and Rogers 1999). Based on these findings it was decided to seek alternatives to the injectable transponders, and that the rumen was an appropriate location for an electronic identification transponder. The electronic industry in addition to incorporating existing technology into developing a rumen bolus also developed a transponder specific to the rumen.
Ceramic Bolus
The various ceramic boluses commercially available adopted a technology whereby an injectable transponder was encased in a ceramic cylinder. The ceramic case produced the necessary size and density to ensure that the bolus was retained in the rumen/reticulum. Caja et al. (1999) reported that zero porosity and atoxic ceramic material (alumina, Al203) of high specific weight (>3.3 g/cm3) was used to produce a bolus for enclosing different types of glass encapsulated transponders (Caja and Vilaseca 1996, Caja et al. 1997). Shape (cylindrical, with truncated edges in the extremes) and features (external diameter, 20 mm; length, 66 mm; weight, 65 g) of the bolus were designed in order to make its oral administration to young and adult animals possible and to ensure its permanent retention in the fore-stomach of sheep, goats and cattle. A drill hole of 7 x 45 mm in the center of one of the bases made sufficient room for enclosing different types of glass encapsulated transponders. The boluses were sealed with epoxy resin (MP Super, Ceys S.A., Barcelona, Spain). Final weight of sealed boluses was > 67 g. The ceramic cylinder was encapsulated with a plastic coat.
Similarly, Ferri et al. (2000) reported on a bolus for bovines (66 mm long, 20 mm in diameter, weight 63 g and density of 3.6 g/cm3) where the ceramic material is used to shield the transponder (Figure 2). The ceramic vane for transponder is made by a dry powder (alumina - A1203 - 96%) cold pressed and then fired at 1580°C for 10 hours, while the transponder is a commercially available product of Texas Instruments Inc. (TIRIS, reading rate of 120 msec).
Figure 2. Exploded schematic drawing of ceramic bolus (courtesy of Innoceramics).
Monolithic Bolus
In the United States in co-operation with AVID ID Systems, EZ.ID is co-developed a new monolithic bolus and it was introduced as the EZ.ID rumen bolus in 2001. Under a joint development agreement with the bolus manufacturer Du Pont specialists developed a special heavyweight grade of Hytrel and provided assistance in mold design and processing techniques. The monolithic (overmolded) rumen bolus weights 72 grams and is 68.5 mm long with a diameter of 21.5 mm.
Steel Weighted Bolus
In the Netherlands Nedap Agri developed a weighed electronic bolus specifically for use in the rumen (Figure 3). The main feature is a glass cylinder containing the electronic components. The passive radio frequency identification (RFID) tag is integrated in a glass capsule to protect it against penetration of rumen fluids. To withstand damage the glass capsule is integrated in a plastic protective casing with damping material. (Figure 3) A stainless steel weight attached to the electronic rumen bolus is positioned eccentrically to enable swift submersion through the rumen surface.
The electronic life number is also visibly printed on the bolus. This enables easy identification and recording before application without the necessity of a RFID reader. Also, it provides a back-up in the slaughter process, in the unlikely event of the radio frequency identification part in the bolus being defective.
Figure 3. Schematic drawing of steel weighted bolus (courtesy of Nedap Agri)
Readers
There are basically two types of readers used which are either the static or portable type. The static readers would be located in facilities with a large throughput of livestock such as livestock marts, abattoirs, feedlots or cattle export premises. The static reader would automatically read the animal as it passed through the reading field. The electronic ID would be stored and downloaded into a data base containing an information file relating to that animal. The portable reader would operate on farms and the electronic identity of the animal would be linked to a veterinary inspection or other management procedures.
Bolus administration
In respect to ruminating cattle more than 100 kg liveweight the administration procedure is similar to that used to insert anthelminthic boluses i.e. administer orally by the use of an oesophygeal balling gun which delivers the bolus directly into the top of the gullet. The bolus should be inserted into the applicator as directed. The applicator should be inserted from the front (not sides) of the mouth and over the back of the tongue, with no more than gentle firm pressure. As the animal begins to swallow the end of the gun, the passage down the throat becomes easier. The applicator is now in position for firing. The trigger is squeezed to eject the bolus. Normal care should be taken not to cause any injury by placing the applicator too far inside the throat of the animal. Ensure that each animal has swallowed the bolus by observing the animal for a short time after dosing.
In the European Community there is a legislative requirement for all bovine animals to be officially identified within 4 weeks of birth. This would necessitate the insertion of the bolus at a time prior to full development of the rumen/reticulum. In respect to young calves > 2 weeks of age a different approach is required. Caja et al. (1999) reported that the application of a rumen bolus was
possible in milk fed calves (> 30 kg). Stimulation of the involuntary deglutition reflex by placing the bolus in the oropharynx seems to be a key practice for safe application in young animals (Caja et al. 1999). The same authors also reported some difficulties with swallowing with four milk-fed calves (4.1%) in the first week of life. In these cases the bolus descent was helped by a downwards massage on the throat and neck or the bolus was retrieved by upwards massage and the application delayed for 1 week. No injuries or accidents were produced to the animals during the application of the new ceramic boluses used. Analogous results were reported by Hasker and Bassingthwaighte (1996) with ceramic capsules of similar dimensions but lower weight (60 x 20 mm. 40 g) in cattle.
Muller (1998) concluded that the procedure of administering electronic boluses to neonatal calves should aim at introducing the device directly into the ruminoreticular compartment in order to prevent oesophygeal obstruction or passage of the bolus to the abomasum. An applicator was developed for use with the steel weighted bolus that allows administration of electronic boluses directly into the ruminoreticular compartment of neonatal calves (Figure 4). The dimensions of the applicator are based on those of oesophygeal tubes that are well known by farmers for years. The latter devices are used to administer colostrum or electrolyte solutions to neonatal calves. These conclusions are supported by the proposal (Muller 1998) that a technique that is suitable for oral administration of electronic boluses has to aim at introducing the devices into the forestomach compartment (reticulorumen) but not into the abomasum of the newborn calf. Foreign bodies present in the lumen of the abomasum of calves have been shown to cause severe harm by irritating the mucous membranes by occluding the omasal or abomasal or pyloric orifice (Welchman and Baust 1987). In contrast to these findings, hardly any complications have been described concerning boluses or magnets that have been deposited into the reticulum of adult cattle.
In order to introduce the bolus into the reticulorumen compartment, closure of the reticular groove has to be circumvented. Previous studies have shown that capsules with a diameter of 6 mm and a length of 31.6 mm reach the reticulum if no liquids are consumed during administration (Muller 1998). In contrast, the capsules passed through the oesophygeal groove to the omasum when at the same time the animals were allowed to drink milk. Although these findings show that it is more likely that the bolus would reach the reticulum when administered by hand, there still remains a certain risk that contraction of the oesophygeal groove could result in deposition of the bolus in the omasum or even in the abomasum. Bolus guns (length 24 cm) are used to administer therapeutics to ruminating calves (Figure 4). These bolus guns have to be inserted into the mouth as far as the pharyngeal region to stimulate the reflex of swallowing. By this means chewing or rejection of the bolus is prevented. When bolus guns are used to administer the boluses to neonatal calves it is possible that the electronic bolus, due to its dimensions, could be retained in the oesophygeal lumen (Muller 1998). This assumption is supported by observations from previous studies in which it was possible on several occasions to palpate the bolus in the cervical part of the oesophygus after it was administered using a balling gun. The bolus present in the oesophygeal lumen forms a continuing stimulus for oesophygeal contractions. Spasmodic contractions of the oesophygus at the site of the bolus could result in oesophygeal obstruction (Muller 1998). In addition, the bolus lying in the oesophygeal lumen could pass through the oesophygeal groove to the abomasum at the moment when liquid foodstuffs are consumed. Using bolus guns to administer therapeutics in calves can cause severe problems. Anderson and Barrett (1983) describe severe lesions of the pharyngeal region as well as perforations of the oesophygus caused by excessive force used during oral administration of boluses by means of balling guns.
Figure 4. Examples of long and short bolus applicators.
The technique using a long bolus applicator analogous to an oesophygeal tube will deposit the bolus directly into the rumen/reticulum and elimate thus the risk of the bolus causing blockage of the oesophygus. The long bolus applicator (Figure 3) is 90 cm in length. In autumn 2000 and 2001, the long bolus applicators were successfully used to deposit boluses in the rumen/reticulum of 220 Friesian calves with a mean liveweight of 50 kg (range 36 to 67 kg) without any difficulty (Fallon unpublished). The ability to deposit the rumen bolus directly into the rumen/reticulum using a specially designed applicator is an important development as concern has been expressed with regard to boluses administration to 8 day old calves. A number of calf deaths were directly attributed to the bolus being retained within the oesophagus and other deaths due to damage to the oesophygeal wall which caused infection and death. In all instances it appears the bolus gun had a short range and deposited the bolus at the beginning of the oesophygus. In contrast the long bolus applicator delivers the bolus directly into the rumen/reticulum.
