Key Words: Cattle, Identification, Injection, Tracking, Transponders

Effects of injection position and transponder size on the performances of passive injectable transponders used for the electronic identification of cattle 1,2 C. Conill*, G. Caja*,3, R. Nehring* and O. Ribó *Unitat de Producció Animal, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain and Safeguards and Verification Techniques Unit, Institute for Systems Informatics and Safety, Joint Research Centre, 21020 Ispra, Italy ABSTRACT: A total of 686 Tiris half-duplex passive injectable transponders (PIT) of two sizes (23 and 32 mm) were randomly injected s.c. in three positions, armpit, ear scutulum, and upper lip, in 343 fattening calves (1 to 3 mo old). Injections were performed by two trained and two untrained operators. Losses and breakages on the farm were recorded at wk 1, 3, 7, 11, and 15 in restrained animals using two types of handheld transceivers with a stick antenna. Dynamic reading efficiency (DRE) in animals running through a raceway was also evaluated at wk 1 and 3 and monthly until slaughter, using a stationary transceiver working at 137 db V m 1 at 3 m. The total number of PIT that fell or broke in the slaughtering line, the location method, and the recovery time were also recorded. Results on the farm showed low breakages on average (0.4%) and differences (P < 0.05) in losses according to position (armpit, 1.7%; ear, 5.2%; and lip, 14.0%). An interaction (P < 0.05) between position size was observed, and losses were greatest using a 32-mm PIT in the lip. The DRE was affected (P < 0.05) by PIT position and size, and values were greater for the 32-mm PIT in all positions (armpit: 99.9 ± 0.1 vs 95.8 ± 4.9%; ear: 93.8 ± 2.2 vs 81.9 ± 4.6%; lip: 66.8 ± 4.9 vs 53.4 ± 4.7%, respectively, for 32 vs 23 mm). Recovery of PIT in the abattoir was on average 96.7, 96.7, and 99.2% for armpit, ear, and lip, respectively (P > 0.05). Most of the PIT injected in the armpit were recovered by sight or palpation, but 31.9% were recovered after cutting the muscles around the area and 10.7% were recovered on the internal side of the hide, which jeopardized carcass identification. Recovery of PIT injected in the ear was 23.4% in the hide and 76.6% in the auricular muscles of the head. The easiest recovery was in the lip, 8.9% of PIT were located in the hide and 91.1% in the head. Recovery time was affected (P < 0.05) by position: the quickest was lip (27 ± 2 s), followed by ear (52 ± 5s) and armpit (78 ± 7 s). In conclusion, taking into account retention and reading performances, injection of a 32- mm PIT into the armpit showed the best results on the farm, but a careful and longer recovery was needed in the abattoir. Improvement of recovery methodology and time would be necessary in order to recommend injection of PIT in the armpit instead of in the ear for cattle tracking or monitoring. Key Words: Cattle, Identification, Injection, Tracking, Transponders 2000 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2000. 78:3001 3009 Introduction Traditional identification methods (e.g., branding, ear tags, tattoos, ear notches, and freeze marks) are not optimal for identification in cattle herds. Electronic identification using passive (without batteries) transponders can improve control and management of cattle. Transponders can be embodied in plastic and used 1 Research supported by The European Commission, General Directorate of Agriculture (DG-VI), Program AIR3, Contract AIR 3 PL 93 2304 (Coupling Active and Passive Telemetric Data Collection for Monitoring, Control and Management of Animal Production at Farm and Sectorial Level, 1995 97). Received February 29, 2000. Accepted July 12, 2000. as ear tags (Sherwin, 1990; Stärk et al., 1998), covered by a capsule of biomedical glass and injected under the skin (Gruys et al., 1993; Lambooij et al., 1995; Caja et al., 1998), or placed into a bolus to be introduced into the forestomach of ruminants (Fallon and Rogers, 1996; Hasker and Bassingthwaighte, 1996; Caja et al., 1999). 2 The authors appreciate the assistance of Ganados Font and Ramón Costa for feeding and taking care of the animals; Celina Torre and Joan Riera (Agribrands Europe-España, Barcelona) and Joan Vilaseca and Ovidi Aguilar (Gesimpex Com., Barcelona) for technical support and advice; the Direction and Veterinary teams of the abattoirs of Castellbisbal, Palleja, and Viñals in Barcelona for the slaughtering facilities; and Nic Aldam for the English revision. 3 Correspondence: fax: +34-93 5812006; E-mail: gerardo. caja@uab.es. 3001

3002 Conill et al. Figure 1. Glass encapsulated passive injectable transponders (upper: 32 mm; lower: 23 mm). The main advantages of passive injectable transponders (PIT) are related to their small size, allowing an early injection in young and small animals, and the possibility of both animal and carcass identification (Caja et al., 1998). Several studies have been carried out in cattle using PIT injected s.c. in different positions, including the ear-base or under the scutulum of the ear (Fallon and Rogers, 1991; Oakley, 1993; Hasker and Bassingthwaighte, 1995), the anal region (Hasker et al., 1992), and the armpit (Luini et al., 1995; Lambooij et al., 1999). At present, results obtained varied according to PIT technology, injection procedures, and experimental conditions. Nevertheless, injection under the scutulum is currently preferred when PIT are used in cattle (Fallon and Rogers, 1991; Klindworth et al., 1999; Lambooij et al., 1999). The aim of this work was to evaluate effects of injection position, transponder size, and previous operator training on reading and recovery performances of PIT used for electronic identification of cattle under intensive conditions. Earlier results were published by Conill et al. (1996, 1998). Materials and Methods Animals, Transponders, and Injection Procedures A total of 686 half-duplex and read-only PIT (Model Ri-Trp-RC2B, Tiris, Texas Instruments, Almelo, The Netherlands) 32 (n = 383) and 23 mm in length (n = 303, Figure 1) were used to identify 343 fattening calves (1 to 3 mo old). The PIT were injected (s.c.) in three positions: armpit (n = 343), ear scutulum (n = 193), and upper lip (n = 150). Serial numbers of the PIT ranged from 340,046 to 8,381,320, indicating that they were manufactured by Texas Instruments (Almelo, The Netherlands) after 1992, with a hard green biocompatible glass 0.33 mm thick (Caja et al., 1998). Thirty-three animals (9.6%) were Holstein-Friesian male calves and 310 (90.4%) were female calves of the Asturiana breed (a local Spanish beef cattle breed) and its crossbreeds with Holstein Friesian, Limousin, Charolais, and Belgian Blue. All calves were under an intensive fattening system that included rearing with artificial milk until 3 mo of age and ad libitum access to a commercial concentrate (Ternicarn 2A, Agribrands Europe-España, Barcelona) and straw to produce pink-beef labeled meat (Gabricarn, Agribrands Europe-España, Barcelona). Each calf was tagged with a conventional plastic ear tag (Allflex, Vitré, France or Ardes, Bourgoin, France, depending on the farmer preferences) and injected s.c. in two positions (Figure 2): left armpit (Caja et al., 1994, 1998) and left ear scutulum (Klindworth et al., 1999) or left part of the upper lip (Lambooij et al., 1999). Calves were reared according to the European Union standards (Directive 91/629/EEC, amended by the Commission Decision of February 24, 1997) and injections were performed with calves restrained in head-lockers after milk feeding by one operator and one assistant. The armpit (regio axillaris) injection resulted in the PIT being placed in the space between the thoracic wall and the caudal muscles of the left arm (triceps brachii). The ear (cartilago scutiformis) PIT was placed into a depression just in front of the apex of the cartilage and approximately on the midline of the ear. The lip (regio labialis superior) PIT was inserted s.c. approximately 10 cm to one side of the center of the nose and 10 cm caudal, in a dorso-ventral direction. A multi-shot injector (Model Ri-inj-002A, Tiris, Texas Instruments) equipped with a 60-4.8-mm needle (Model Ri-ndloo2a) was used for the injection into the armpit and a single-shot injector (Model Ri-inj-003C, Tiris, Texas Instruments) with a 73-4.5-mm needle (Model Rindl-oo3c) was used for the injection in the ear and lip. The PIT were received in cartridges of 10 and immersed in an iodine gel solution (Betadine oplossing, Dagra, The Netherlands). Another iodine solution (Braunol, B. Braun Medical, Jaén, Spain) was used to spray the injection site before and clean the needle after each injection. Injections were performed by four operators working in two teams of different skill levels; either trained (with more than 1,000 PIT injected previously) or untrained (taught at the beginning of the injections). All operators were untrained for injection in the lip but they were classified for this trial according to their previous experience with injecting PIT in other locations. Transceivers and Reading Efficiency Each PIT was immediately read after injection using an intelligent hand-held transceiver with a built-in keyboard and a stick antenna (Portoreader, Insentec, Marknesse, The Netherlands), and the conventional ear tag number and the relevant data of the animal at tagging (age, sex, coat color, breed, and observations) were typed and automatically linked to the PIT number. Reading performances were evaluated in static and dynamic conditions as proposed by Caja et al. (1999).

Injectable transponders in cattle 3003 Static reading efficiency or readability (PIT that had been read/pit injected) as a percentage was determined in restrained animals using two different types of handheld transceivers (Portoreader and Gesreader I, Gesimpex Com., Barcelona, Spain) at wk 1, 3, 7, 11, and 15. Losses, breakages, and possible disturbances (infections, injuries, etc.) were checked at each static reading and, at the same time, the absence of breakages was ensured by palpation. Dynamic reading efficiency (PIT that had been read/pit readable) as a percentage was evaluated with animals in movement using two portable raceways (0.5 and 0.8 m wide), according to the size of the animals. A 94-52-cm frame antenna (Riant-g03c, Tiris) was placed on the left side of the raceway and connected to a stationary reading unit (Model S-1000, Gesimpex Com.), working at 137 db V m 1 at 3 m. The center of the antenna was oriented to be equidistant to the three injection body positions (Figure 2). The communication with a portable personal computer was performed via RS-232 interface. A software program (Manga v.5.3, Gesimpex Com.) was used for module activation and electronic data collection to obtain a final reading report of the dynamic reading. Dynamic reading efficiency was evaluated at wk 1 and 3, and then monthly until slaughter. An additional static reading was made in the animals whose PIT were not read in the dynamic readings to check for losses, breakages, and electronic failures. Slaughtering and Transponder Recovery Animals were slaughtered according to local preferences when they reached marketable weight (approximately 250 kg hot carcass) between 9 and 12 mo old, in five commercial abattoirs (40 to 60 animals/h). Retention of plastic ear tags was recorded at the start of the slaughtering line. Skin removal was done by mechanical traction with manual help in 95% of cases. Location of PIT in the abattoir was carried out using the two types of hand-held transceivers equipped with stick antennas (Portoreader and Gesreader I). The PIT number was read at the start of the slaughtering line and recovery was performed at the end of the line, before the release of the carcass. Total PIT losses (fell out or broken) in the slaughtering line, the PIT location method within each injection area (by sight, palpation, or cutting), and total recovery time from the carcass or from the head, for each injection position, were also recorded. Heads were collected in containers after separation from the body to retrieve the PIT in ears and in lips. Hides were also checked using a hand-held transceiver to detect the presence of PIT, and they were manually removed when necessary. The absence of broken or electronically failed PIT in the heads and in the carcasses was verified using a highly sensitive metal detector (Type GM 17, Gelan, Tiris). All carcasses were inspected by the veterinarian service of each abattoir before release and grading. Figure 2. Injection procedures for the electronic identification of cattle (AR: armpit, ES: ear scutulum, UL: upper lip, FA: frame antenna).

3004 Statistical Analysis In order to study effects of the experimental factors on losses, breakages, and readability on the farm and losses, breakages, place of location (carcass, hide, or head) and location method (sight, palpation, or cut) within each injection area in the abattoir, the conventional linear type statistical models were not appropriate due to the dichotomy of the variables. For this reason, a logit model with the estimation method of maximum likelihood (Cox, 1970) was chosen. The CAT- MOD procedure of SAS (SAS Inst. Inc., Cary, NC) was used, and factors and interactions that were not significant (P > 0.20) were removed from the model. Due to the low number of PIT broken (3 of a total of 686 injected, and 1 of 635 that arrived at the abattoir) it was not possible to apply the statistical analysis to this case. Injection time and dynamic reading efficiency results were analyzed by analysis of variance using the GLM procedure of SAS. Factors and interactions that were not significant (P > 0.20) were also removed from the model. The recovery time was also analyzed by analysis of variance using the GLM procedure of SAS and the factors and interactions that were not significant (P > 0.20) were removed from the model. Recovery times were transformed into the inverse of the square according to the Box-Cox transformation method (Draper-Smith, 1981). Statistical significance was declared at P < 0.05 and, following a significant F-test, means were separated using the Tukey test of SAS. Results and Discussion General means of the effects of injection position, PIT size, and operator skill on the farm are shown in Tables 1 and 2. Time required to place the PIT into the lip (51 ± 4 s) was greater (P < 0.05) than for the armpit (37 ± 3 s), and ears required an intermediate time (44 ± 3 s). These results were expected, because a complete immobilization of the head was required in order to perform a proper injection into the lip and ear. Untrained operators took more time than did skilled technicians to perform the injection in the armpit and lip (P < 0.05). However, times recorded were less than 1 min in all cases, which was the approximate time estimated by Klindtworth et al. (1999) for the specific injection of PIT into the ear. These results are similar to those obtained by Luini et al. (1995), who needed about 50 s for injections into the armpit and ear. Health status and average daily gain (1.4 ± 0.2 kg/ d) of calves were apparently unaltered by the PIT injection, suggesting that identification of animals using s.c. PIT does not compromise animal performance. However, some local effects were observed. Amaig calves with PIT in the ear, six (3.1%) bled after injection; the lips of seven calves (4.7%) were pierced during the lip Conill et al. injection. In this latter case, animals were reinjected in the same position 1 wk later to avoid losses produced by errors during the injection procedure. Moreover, in five animals injected in the lip (3.3%) and in four injected in the ear (2.1%), small infections with formation of an abscess with pus and rejection of PIT were observed. This finding compromises the ear and lip injection of PIT under practical conditions and is a major concern in regard to animal welfare. The main reason for the appearance of these infections was probably a contamination during the injection procedure. As described by Gelmetti et al. (1994), injections causing abundant bleeding and the accidental presence of hair debris cause a more severe inflammation with granulomatose reaction, hyaline degeneration of muscle fibers, and steatite. The same authors described that the resolution of trauma injection is better when body regions are rich in subcutaneous collagen and poorly perfused. For this reason, PIT injected into the armpit showed only a mild inflammatory reaction compared with other PIT injection sites. Total percentage of PIT broken was 0.4%. This low number of cases made the statistical treatment of this variable impossible. This value was slightly less than the average obtained by Luini et al. (1996), who reported breakages of 0.3% in the ear and 0.9% in the armpit, using the same type of PIT, and less than the average reported by Fallon and Rogers (1991), Oakley (1993), and Lambooij et al. (1999). This probably was a consequence of the improved features of PIT used in this work (Caja et al., 1998) and the shorter fattening period. Klindtworth et al. (1999) indicated that an increase in breakage may be expected as transponder length increases in laboratory conditions, but their in vivo results included losses and breakages as total failures. Percentage of readable PIT decreased with time in the ear and lip positions (P < 0.05) but not in the armpit (Figure 3). Main PIT losses occurred during the 1st wk after injection (62.2%) and were associated with rejection, because of a rapid withdrawal of the needle, or insufficient penetration depth, as described by Lambooij et al. (1995), followed by an immediate PIT rejection through the entrance hole. At wk 3, 84.0% of the total losses was recorded. Generally, losses later than 1 wk were probably due to an inflammatory reaction with an incomplete healing in the injection area. Lambooij et al. (1995) found that abscesses in pigs may remain in place during the fattening period or may break, resulting in the late expulsion of the transponder. In our results, only one abscess was observed in the ear at the end of the fattening period. Mean percentages of PIT losses were 14.0% in the lip, 5.2% in the ear, and 1.7% in the armpit (Table 1). Losses were greater (P < 0.05) in the lip than in the armpit. These percentages are similar to those obtained by Luini et al. (1996), who reported 5.4% in the ear and 1.6% in the armpit using the same type of PIT, but less than those reported by Lambooij et al. (1999), who used

Injectable transponders in cattle 3005 Table 1. Effects of injection position a and transponder size on farm readability in cattle AR ES UL SE Injection time, s 32 mm 36 42 50 4.1 23 mm 39 46 54 5.2 Overall 37 x 44 xy 51 y 3.2 NS NS NS Lost transponders, n (%) 32 mm 2 (1.0) 8 (7.0) 18 (24.3) 23 mm 4 (2.7) 2 (2.6) 3 (3.9) Overall 6 (1.7) x 10 (5.2) xy 21 (14.0) y NS NS * Broken transponders, n (%) 32 mm 1 (0.5) 0 1 (1.4) 23 mm 0 0 1 (1.3) Overall 1 (0.3) 0 2 (1.3) Failed transponders, n (%) 32 mm 0 0 0 23 mm 0 0 0 Overall 0 0 0 Readability, n (%) b 32 mm 191 (98.5) 107 (93.0) 55 (74.3) 23 mm 145 (97.3) 76 (97.4) 72 (94.7) Overall 336 (98.0) x 183 (94.8) xy 127 (84.7) y NS NS * a Abbreviations: armpit (AR); ear scutulum (ES); upper lip (UL). Sample sizes: AR = 343 (194 and 149 for 32 and 23 mm, respectively); ES = 193 (115 and 78 for 32 and 23 mm, respectively); and UL = 150 (74 and 76 for 32 and 23 mm, respectively). b Readability = (transponders read /transponders injected) 100. x,y Row values with different superscripts differ (P < 0.05). Table 2. Effects of injection position a and training of operators on farm readability in cattle AR ES UL SE Injection time, s Trained 33 45 46 3.9 Untrained 44 44 60 4.8 Overall 37 x 44 xy 51 y 3.2 * NS * Lost transponders, n (%) Trained 1 (0.5) 2 (2.6) 16 (16.5) Untrained 5 (3.8) 8 (7.0) 5 (9.4) Overall 6 (1.7) x 10 (5.2) xy 21 (14.0) y Broken transponders, n (%) Trained 1 (0.5) 0 1 (1.0) Untrained 0 0 1 (1.9) Overall 1 (0.3) 0 2 (1.3) Failed transponders, n (%) Trained 0 0 0 Untrained 0 0 0 Overall 0 0 0 Readability, n (%) b Trained 210 (99.1) 76 (97.4) 80 (82.5) Untrained 126 (96.2) 107 (93.0) 47 (88.7) Overall 336 (98.0) x 183 (94.8) xy 127 (84.7) y a Abbreviations: armpit (AR); ear scutulum (ES); upper lip (UL). Sample sizes: AR = 343 (212 and 131 for trained and untrained, respectively); ES = 193 (78 and 115 for trained and untrained, respectively); and UL = 150 (97 and 53 for trained and untrained, respectively). b Readability = (transponders read /transponders injected) 100. x,y Row values with different superscripts differ (P < 0.05).

3006 Conill et al. Figure 3. Evolution of readability (transponders read/transponders injected 100) of passive injectable transponders according to different positions. 19- and 28-mm PIT in the lip (10.1%), ear (22.2 to 25.8%), and armpit (3.4%). Regarding PIT size, losses in the lip were greater (P < 0.05) with 32- than with 23-mm PIT (24.3 vs 3.9%, respectively), whereas in the ear and armpit losses were not affected by PIT size. These results agreed with those obtained by Klindtworth et al. (1999) and Lambooij et al. (1999) and could have been a consequence of the large PIT that was injected. Plastic ear tag losses observed during the experimental period until the slaughtering of the animals (9 to12 mo old) were 11.4%, giving a lower readability value (P < 0.05) than that obtained for the armpit and ear, but higher than that for the lip. As a consequence of losses and the low number of breakages, the PIT readability was greater (P < 0.05) in the armpit (98.0%) than in the lip (84.7%), and mean percentage obtained in the ear was 94.8% (Table 1). The greatest readability value was obtained with the 32-mm PIT injected into the armpit (98.5%). This result agrees with the recommendation (> 98%) of the International Committee for Animal Recording and is comparable to the one obtained by Luini et al. (1995) using the same type of PIT in beef cattle (97.9%). Values of readability obtained by Lambooij et al. (1999) with a 28-mm PIT injected into the armpit of beef cattle were slightly less (96.6%). These results suggest that the armpit region has enough room to shelter a 32-mm PIT and also allows quick scarring of the entrance hole, which reduces the percentage of losses after injection. To the contrary, results obtained in the ear and lip suggest that neither position allows enough room for a 32-mm PIT. Moreover, it is expected that shaking movements of the heads of the animals facilitate the PIT rejection shortly after it is injected. Similar results were obtained for the ear by Luini et al. (1995), with readability values of 97.7 and 92.7% for 23- and 32-mm PIT, respectively. Results obtained by Lambooij et al. (1999) using 28- and 19-mm PIT in the ear were less (86.4 and 68.7%, respectively) and contrary to expectations. However, the full duplex technology used by Lamboij et al. (1999) was more sensitive to interference, and for this reason PIT readability was probably reduced as a consequence of greater electronic PIT failures. The lip was the location where the animal showed more reaction during the injection procedure. Moreover, the percentage of losses, mainly with the 32-mm PIT, was too high to recommend this position for practical conditions. These results were confirmed by Lambooij et al. (1999) using a 19-mm PIT, in which readability was 89.9%. Percentage of losses was unaffected by the training of operators (Table 2). These results suggest that electronic identification of cattle using PIT is a simple task and is easy to learn by inexperienced technicians. The mean results of dynamic reading efficiency are represented in Figure 4. Dynamic reading efficiency was statistically affected (P < 0.05) by injection position and PIT size. Values were high for the armpit, medium for the ear and low for the lip. In all positions, reading efficiency was greater (P < 0.05) when animals were injected with 32- than with 23-mm PIT (99.9 ± 0.1 vs 95.8 ± 4.9% in the armpit; 93.8 ± 2.2 vs 81.9 ± 4.6% in the ear, and 66.8 ± 4.9 vs 53.4 ± 4.7% in the lip). Dynamic reading efficiency was only greater than 99% with the 32-mm PIT injected into the armpit, but it was also high (> 93%) for the 23-mm PIT injected into the armpit and the 32-mm PIT injected into the ear. Values of dynamic reading efficiency depend on several factors, such as PIT size and transceiver field strength (Conill, 1999; Klindtworth et al., 1999). The dynamic reading efficiency was greater with the 32-mm PIT than with the 23-mm PIT (P < 0.05) in all positions (Figure 4). Moreover, reading efficiencies can be explained by

Injectable transponders in cattle 3007 Figure 4. Dynamic reading efficiency (DRE: transponders that have been read/readable transponders 100) of passive injectable transponders in cattle at 137 db V m 1 at 3 m. Differences between 23- and 32-mm transponders were significant (P < 0.05) at all locations. the position of the PIT inside the electromagnetic reading field of the antennas (Nehring et al., 1994) and by the movements of the body position when animals are walking or running through the raceways. The PIT in the armpit maintained a centered position in relation to the antenna and allowed the greatest values of dynamic reading efficiency, whereas head movement as the animal passed through the raceway may exclude the PIT injected in the ear or lip from the reading field. Thus, the values of dynamic reading efficiency were greater in the armpit region in all cases. When the PIT lost on the farm (5.4%) and PIT injected in animals that died (2.0%) during the fattening period (for reasons not related to the injection procedure) were excluded, the total percentage of PIT that arrived to the slaughterhouse was 92.6% (n = 635). Transponder losses and recovery in the slaughterhouse are shown in Table 3. Percentages of PIT retrieved varied in the range of 99.2% in the lip to 96.7% in the armpit and ear. In consequence, total losses ranged between 0.8 and 3.3%, respectively (P > 0.05). The percentage of losses obtained with lip injection (Table 3) agreed with the desirable recovery value according to the recommendation of < 1% by the International Committee for Animal Recording. This result was a consequence of the lip not being a cutting zone in the slaughtering procedure. The percentage losses for the armpit and ear (3.3%) need to be improved for a generalized use of s.c. PIT. The presence of macroscopic lesions in the carcasses (armpit) and head (ear and lip) corresponding to injection position was not observed in any case. Transponders seemed to be surrounded by a thin but very resistant fibrous capsule, as described by Luini et al. (1996). Results of PIT location in the carcass, head, or hide during the slaughtering process, and their distribution according to recovery method (Table 4), were statistically analyzed separately for each injection position due to the lack of homogeneity of the body regions. Transponder size and operator skill did not affect (P > 0.05) the distribution according to recovery method within each injection position. Nevertheless, location on the head or hide for ear injections was affected (P < 0.05) by operator skill (data not shown). The armpit region, which showed the highest readability and dynamic reading efficiency on the farm, is a suggested region for PIT injection in ruminants because it can allow both animal and carcass identification. Nevertheless, our results indicate that a total of 10.7% of PIT were recovered on the internal side of the hide, the remainder (89.3%) being recovered from the carcass. Recovery from the hide was easy and quick (< 8 ± 4 s) because 91.2% of PIT were located by sight. These results indicate that traceability was interrupted during the slaughtering procedure in 10.7% of carcasses, which reduces the interest of the injection in the armpit under practical conditions. Similar results were obtained by Luini et al. (1996), with 15.2% of PIT retrieved from the internal side of the hide, and by Lambooij et al. (1999) using different PIT types. The distribution according to recovery method in the PIT injected in the armpit (Table 4) suggests a laborious recovery and the need for a previous recovery training, particularly for the PIT injected into deep positions (31.9%). Table 3. Disposition of injectable transponders in beef cattle in the slaughterhouse Injection position a Size mm Operator PIT Item number AR ES UL 23 32 Trained Untrained PIT arrived 635 330 180 125 288 347 361 274 Losses, n (%) 20 11 (3.3) 6 (3.3) 1 (0.8) 6 (2.1) 12 (3.5) 11 (3.0) 7 (2.6) Recovery, n (%) 615 319 (96.7) 174 (96.7) 124 (99.2) 282 (97.9) 335 (96.5) 350 (97.0) 267 (97.4) Ear 171 (98.3) Head 2 (1.1) 124 (100) Carcass 285 (89.3) 0 0 Hide 34 (10.6) Broken 0 1 (0.6) 0 0 1 (0.3) 1 (0.3) 0 Recovery time, s 75 ± 8 x 52 ± 5 yz 27 ± 2 z 55 ± 7 63 ± 6 60 ± 6 59 ± 7 a Abbreviations: armpit (AR); ear scutulum (ES); upper lip (UL). x,y,z Row values within injection position, size, or operator categories with different superscripts differ (P < 0.05).

3008 Conill et al. Table 4. Location and distribution of transponders injected in different positions a according to recovery method in the slaughterhouse AR ES UL Item Hide Carcass Hide Head Hide Head Transponders present, % 10.7 89.3 23.4 76.6 8.9 91.1 Recovery method, % Sight 91.2 44.2 17.1 7.5 36.4 0 Palpation 8.8 23.9 17.1 6.0 45.5 87.6 Cut 0 31.9 65.8 86.5 18.1 12.4 a Abbreviations: armpit (AR); ear scutulum (ES); upper lip (UL). Recovery method was not affected by transponder size and operator skill (P > 0.05). For ear injections, a total of 23.4% of PIT were recovered in the hide and 76.6% recovered in the auricular muscles (Table 4). Percentage of PIT retrieval in the hide was greater (P < 0.05) for untrained than for trained operators (31.7 vs 11.3 %, respectively), probably because the untrained operators introduced the needle less deeply under the skin. Contrary to results for PIT injected into the armpit, most of PIT in the ear were recovered by cutting. Only one PIT (0.6%) injected into the ear was broken during slaughtering. In the lip, recovery from the hide was 8.9% and that from the head was 91.1%. The distribution according to recovery method was approximately 36:46:18 for sight:palpation:cutting from the hide and 0:88:12, respectively, from the head. Concerning apparent migration, the percentage of PIT recovered displaced from the injection area was low for all locations: lip (0%), ear (1.7%), and armpit (1.6%). Transponders that migrated in the armpit were easily recovered by sight on the ribald zone. For PIT injected in the ear, due to the low possibility of migration in this region (Hasker and Bassinghwaighte, 1996), the percentage of PIT recovered from the area was probably a consequence of the wrong location of cartilago scutiformis in the injection procedure. These results agreed with those obtained by Luini et al. (1996) and Lambooij et al. (1999). Recovery time was affected by injection position (P < 0.05). The quickest mean recovery time was observed in the lip (27 ± 2s), followed by the ear (52 ± 5s) and the armpit (75 ± 7s). Although the lip was the region with the quickest recovery time, the unsatisfactory results obtained under farm conditions (readability and dynamic reading efficiency) preclude the recommendation of this region in practice. In the other positions, the recovery times showed a markedly skewed distribution. Percentage of recovery in ear and armpit during the first 20 s was 36.3 and 57.2%, respectively; 64.9 and 68.7% before 40 s; and 78.6 and 73.1% before the 1st min. Mean recovery times increased as a result of migrated or deep PIT, which led to 3 and 10.3% of PIT injected in the ear and armpit, respectively, needing more than 4 min to be recovered. These results impose a low speed of slaughtering (< 70 animals/h) if animals are identified by PIT. This yield was less than that obtained in present commercial slaughterhouses (140 to 180 animals/h). The PIT recovery was easier in hot than in cold carcasses. The recovery time we observed was greater than those obtained by Luini et al. (1996) in the armpit (4 s) and those of Lambooij et al. (1999). The differences are mainly due to the fact that, in both trials, PIT were easily located by sight because they identified young calves for white meat veal production, slaughtered at light weights with a low percentage of fat. Moreover, they did not include recovery times of migrated and deeper PIT in mean recovery time calculations (4% of PIT with recovery time greater than 5 min). For these reasons, in all cases the recovery is recommended off the slaughtering line, in the offal plant after removal of the head (ear or lip) or at the end of the line (for the armpit) before the release and cooling of the carcass. Implications The electronic identification of calves using passive injectable transponders did not produce apparent disturbances to the animals. Results obtained under farm conditions (percentage of losses, readability, and dynamic reading efficiency) with 32-mm transponders injected in the armpit region suggest this position as reliable and feasible for electronic identification in beef cattle, compared with injection into the ear scutulum or upper lip. However, a more careful and longer recovery was needed in the slaughterhouse, limiting the use of the armpit injection site in modern high-productivity plants. For this reason, an improvement of recovery methodology would be necessary in order to recommend the injection of passive transponders in the armpit instead of ear scutulum for cattle traceability and monitoring. Literature Cited Caja, G., C. Conill, R. Nehring, and O. Ribó. 1999. Development of a ceramic bolus for the permanent electronic identification of sheep, goat and cattle. Comput. Elect. Agric. 24: 45 63. Caja, G., M. Luini, and P. D. Fonseca. 1994. 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