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Three types of ceramic mini-boluses, B1 [13.8 g; 10.5 x 51.0 mm (o.d. x length)], B2 (16.2 g; 12.2 x 42.2 mm), and B3 (20.1 g; 11.2 x 56.4 mm), were used to electronically identify as soon as possible after birth a total of 545 lambs of 3 breeds: Ripollesa (meat breed, n = 274), Manchega (dairy breed, n = 129), and Lacaune (dairy breed, n = 142). Boluses were administered by a trained operator using a balling gun or directly by hand. Lambs were also identified with 2 types of plastic ear tags in the left (temporary, 1.5 g) and the right (permanent, 4.1 g) ears. Lamb and identification device performances were checked during suckling (to wk 5 or 7) and fattening. At 24 kg of BW, lambs were slaughtered (n = 385) or kept for breeding (n = 144). No differences in performance were observed between the 2 dairy breeds, and their data were pooled. Minimum BW for bolus administration was lower in dairy than in meat lambs (P < 0.001). Across breeds, B1 and B3 did not differ in lamb age (27 d) and weight (9.2 kg) at administration, but B2 required older and heavier lambs (33 d and 11.1 kg; P < 0.01). Boluses did not affect lamb performance, but final readability at slaughter differed between B1 and B2 (97.7 and 95.2%, respectively) and B3 (100%), and between ear tags (temporary, 98.1; permanent, 100%). Bolus recovery was 100% in all cases, but the proportion of boluses found in the reticulum varied among bolus type (83.3 to 93.8%; P < 0.05). Three B1 (2%) were recovered from the abomasum. In a second experiment, effects of the intermediate mini-bolus (B2) on diet digestibility were evaluated. Digestibility of control and bolus-administered, Manchega ram lambs (14.9 kg of BW; n = 8) fed ad libitum with 2 pelleted concentrates and barley straw was assessed in digestibility crates. Feed intake and nutrient digestibility were measured in four 21-d periods, during which lambs received the 2 diets consecutively. No differences in intake, growth performance, or nutrient digestibility were observed between control and bolused lambs. In conclusion, the B3 mini-bolus proved to be an efficient device for identification of lambs before weaning (recommended age, >4 wk; recommended BW, >10 kg), allowing a reliable traceability of dairy and meat lambs until slaughter. Key words: digestibility, electronic identification, lamb, rumen bolus

Twelve types of electronic identification ruminal boluses of different dimensions were used to obtain a model for predicting their retention in the forestomachs of sheep. Boluses (n = 1,662) were made of ceramic materials, and their dimensions varied in o.d. (9 to 21 mm), length (37 to 68 mm), volume (2.5 to 21.0 mL), and specific gravity (0.85 to 3.91). Each bolus contained a half-duplex, standardized, glass-encapsulated transponder (32 x 3.8 mm). Boluses were administered to sheep (n = 1,497) of different ages by using the appropriate balling guns, and their retention under semiintensive conditions was recorded for at least 2 yr. When a bolus was lost, the sheep was rebolused with a heavier bolus. All sheep wore 2 plastic ear tags: one for the official control of health programs and the other for farm use. To determine the anatomical limit for a bolus passing through the gastrointestinal tract, the size of the reticulo-omasal orifice was measured in 46 adult sheep (male, n = 14; female, n = 32) that died by causes not related to bolus administration during the experiment. No signs of disease or growth alteration were detected in the bolused sheep. Total ear tag losses during the experiment period were 7.5% on average. Bolus retention (5 to 100%) varied according to bolus features and age of the sheep, but it showed a plateau after 18 mo. Inadequately dimensioned boluses were regurgitated or passed through the gastrointestinal tract and were excreted with the feces. The diameter of the reticulo-omasal orifice in adult sheep differed between male and female (23.1 and 21.8 mm, respectively; P < 0.01) and was greater than the o.d. of the retained boluses. Retention rate was predicted from bolus weight and volume by a logistic regression ([R.sup.2] = 0.997; P < 0.001). When retention data from the literature (59.0 to 100%) were included in the model, the adjustment was slightly lower ([R.sup.2] = 0.967). As a result, the minimum bolus weight estimated to reach a 99.5% retention rate in sheep varied between 16 and 45 g when volume varied between 3 and 22 mL, for boluses with a specific gravity between 2.0 and 5.2. In conclusion, bolus retention rate in sheep varied dramatically according to their features. For safe and efficient retention of electronic identification boluses in sheep, boluses of small volume and diameter (e.g., Key words: electronic identification, ruminal bolus, sheep, traceability, transponder

A total of 1,822 pigs from 2 farms (farm A, n = 1,032; farm B, n = 790) were used to evaluate pig traceability under on-farm conditions by using identification devices (n = 4,434) of different technologies. The devices were visual ear tags (n = 1,533; Model 1, n = 776; Model 2, n = 757), electronic ear tags (n = 1,446; half-duplex, n = 702; full-duplex, n = 744), and intraperitoneally injected transponders (n = 1,455; half-duplex, n = 732; full-duplex, n = 723). A group of 790 pigs wore 3 types of devices, and 1,032 wore 2 devices. Piglets were identified before (wk 1 to 3 of age; farm A) or after (wk 3 to 4 of age; farm B) weaning and intensively fattened until approximately 100 kg of BW. Readability of devices was checked at each farm operation by using standardized handheld transceivers. No negative effects of the identification devices on animal health (mortality rate, 8.4%) or performance were detected. On-farm losses averaged 1.6% for ear tags (visual, 0.8%; half-duplex, 1.9%; full-duplex, 2.7%; P > 0.05) and 1.8% for intraperitoneally injected transponders (half-duplex, 1.7%; full-duplex, 1.9%; P > 0.05). Moreover, 1.4% electronic failures occurred in the electronic ear tags (half-duplex, 2.2%; full-duplex, 0.6%; P < 0.05) but not in the intraperitoneally injected transponders. Final on-farm readability was greater (P < 0.05) for visual ear tags (99.2%) than for electronic ear tags (half-duplex, 95.9%; full-duplex, 96.7%; P > 0.05). Readability for intraperitoneally injected transponders was intermediate (half-duplex, 98.3%; full-duplex, 98.1%; P > 0.05). Electronic devices were in all cases easier and faster to read than the visual ear tags. Visual ear tags and intraperitoneally injected transponders were efficiently retained under conditions of commercial pig farms, which agrees with the minimum values recommended by the International Committee for Animal Recording (>98%). When readability and reading ease were also included as decision criteria, injectable transponders were preferred. Key words: ear tag, electronic identification, injectable transponder, pig, traceability

A total of 1,203 beef calves were used to evaluate 2 series of electronic identification boluses. Calves were intensively fattened and slaughtered at approximately 1 yr of age. Series 1 (n = 576 calves) consisted of 10 types of boluses with the same external dimensions (o.d. x length: 21 x 68 mm) but varying in weight (11 to 75 g) and specific gravity (0.63 to 3.36). Six boluses were made of ceramic (5 prototypes and 1 commercial bolus) and 4 were tubes made of plastic filled with concrete. Series 2 (n = 627 calves) consisted of 3 prototypes and 5 commercial boluses of different ceramic materials varying in external dimensions (o.d.: 15 to 21 mm; length: 39 to 78 mm), weight (20 to 73 g), and specific gravity (3.00 to 3.87). Boluses were administered to milk-fed calves (2 to 5 wk of age) by using adapted balling guns. To determine the anatomical limit for a bolus passing through the gastrointestinal tract, the size of the reticulo-omasal orifice was measured in 90 male and 62 female fattened calves at slaughter. Three calves in series 1 (0.3%) could not swallow the 21-mm (o.d.) bolus at the first attempt and received the bolus 1 wk later. No problems for early administration were found with thinner boluses (o.d. Key words: cattle, electronic identification, ruminal bolus, traceability, transponder

A cost model was developed to compare different implementation strategies of the new European Commission regulation for sheep and goat identification and registration (EC 21/2004) in Spain. Strategies were as follows: 1) conventional identification (CID) by two ear tags; 2) electronic identification (EID) by one bolus and one ear tag; and 3) mixed CID and EID strategy (MID), consisting of CID for fattening stock and EID for breeding stock. Complete and simplified implementations of the regulation were considered as options. Total costs per animal identified for all strategies and options varied according to the implementation option, ranging from [euro] 2.48 and 4.64. The EID was the most expensive strategy ([euro] 4.47 to 4.64) for all implementation options. Cost of CID and MID strategies ranged from [euro] 2.63 to 2.98 and from [euro] 2.48 to 3.03, respectively. The model was submitted to a sensitivity analysis without considering extra benefits of sheep and goat identification. Critical values for which the cost of MID equaled CID depended on strategy and option, and ranged from 7.5 to 11.5% for ear tag losses and from [euro] 1.80 to 3.30 for bolus price. In conclusion, the use of a mixed strategy combining conventional ear tags (animals intended for slaughter) and electronic boluses (breeding stock) seems to be an affordable strategy that fulfills the European Commission regulation requirements for the identification of sheep and goats in Spain. Price reductions for devices and equipment would make the full electronic identification strategy less expensive in the future. Key Words: Animal Identification, Bolus, Cost Analysis, Ear Tag, Electronic Identification