Introduction
In order to guarantee food safety and quality, due to the decreasing
consumer confidence caused by disease outbreaks (BSE, FMD, swine fever,
avian influenza, etc.) and food-related safety hazards (dioxin, melamine,
microbial contamination of fresh produce, etc.), a need for a reliable
traceability system for animals and animal products has emerged.
The World Organisation for Animal Health (OIE) defines animal traceability
as “the ability to follow an animal or group of animals during all stages of
life” (OIE, 2011). The traceability process starts initially with the
identification and registration of animals individually. The “farm-to-fork”
approach in traceability, which requires robust and effective systems, could
be successful only if a reliable and permanent animal identification system
is implemented.
As conventional animal identification methods are ineffective, due to
reasons such as losses, code erasing, short reading distances, transcription
errors, negative effects on welfare, and fraud (Caja et al., 2005), these
systems are also far from satisfying the traceability requirements of the
modern livestock industry. Therefore, electronic identification systems
based on RFID (radio frequency identification) technology have been
developed for permanent animal identification. Electronic identification
considerably facilitates the implementation of traceability systems. Pinna
et al. (2006), who applied a questionnaire to technicians and farmers in
order to determine the practical use of electronic identification systems,
reported that there was satisfaction with and interest in the electronic
identification system because the official animal identification systems
currently used were not satisfactory.
Readability and retention rate of electronic (e-ETs) and visual (v-ETs)
ear tags are affected by ear dimensions, environment, and ear-tag features
(Caja et al., 2014). The retention of e-ETs and v-ETs in lambs has
shown remarkable variability, ranging from 85.4 to 100 % in e-ETs
(Thomas et al., 2006) and 91.7 to 100 % in v-ETs (Caja et al., 1999, 2007;
Conill et al., 2002; Ghirardi et al., 2007). In addition,
the tagging site on the animal's ear is critical for its retention (Caja et
al., 2004). The most common ear-tag placement site in animals is in the
middle of the ear. It is recommended that the ear tags be placed on
the first quarter of the animal's ear between the two cartilage ribs for the
greatest retention in cattle (Buskirk, 2006). Buskirk (2006) reported that
“tags placed too far from the head will increase the probability of
snagging on objects, reducing retention and making the animal's ear
susceptible to tearing”. The placement site together with ear-tag type is
significantly associated with the retention of ear tags and severity of ear
lesions. Taking the species and rearing system into account, ear tags should
be applied to a site that cannot damage the ear or cause too much ear-tag
loss.
In Turkey, all sheep and goats have been identified with official plastic ear
tags, vaccinated against PPR disease and recorded in the TURKVET database,
countrywide. However, from 2015, electronic identification using e-ETs has
been implemented within the electronic identification and registration
system for sheep and goats in order to follow animal movements and control
animal diseases. Literature review demonstrated that there were no studies
on the use of e-ETs for electronic identification of lambs in Turkey, and
literature on the effects of placement site on retention of ear tags was not
available. The objective of this study was to evaluate the effectiveness of
electronic and visual ear tags in animal traceability and to investigate the
effect of placement site on ear-tag retention in Akkaraman lambs under rural
conditions.
Material and methods
Administration and monitoring of identification devices
The experimental procedures were approved by Yüzüncü Yıl
University Ethical Committee on Animal Experimentation (reference no
2012/06). Akkaraman lambs used in this study were reared under extensive
conditions in a rural farm in Van province in eastern Turkey. A total of 380
lambs born in the 2014 lambing season were identified with e-ETs (Allflex)
applied on left ears and v-ETs officially approved by the Republic of Turkey
Ministry of Food, Agriculture and Livestock on right ears. Birth date, birth
weight, birth type, gender, ear tag number, and identification number and
age of dam were recorded at time of birth. Lambs were kept with their dams
in a barn for 20 days after lambing. Then, lambs were separated from their
dams during the daytime and kept together during the night-time until weaning
(4 months of age). There was a separate pen for pregnant ewes and lambs,
and concrete water troughs in the barn. The barn was surrounded by a large,
wood-fenced yard. There were wooden feeders in the yard. Lambs and dams were
kept as separate flocks on pasture.
Electronic ear tags containing an FDX-B (full-duplex B) transponder and working at
an activation frequency of 134.2 kHz in accordance with ISO 11784 and 11785
standards (ISO, 1996a, b) were used. The button–button e-ET had a weight of
6.6 g and diameter of 27.5 mm. The flag-type v-ET's total weight was 4 g and
the dimensions for female and male pieces were 38 × 40 and 38 × 35 mm,
respectively. Both types of ear tags, which were tamper-proof, plastic (polyurethane), and yellow in color, also had a laser-printed unique
identification number. The ear tags used are displayed in Fig. 1. In order
to investigate the effect of placement site on retention of ear tags, both
ear-tag types were applied on the same animal either at the mid-point part
(1/2) or the first-quarter part (1/3) of the ear from the head side.
Electronic and visual ear tags used for the identification of
lambs.
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The retention rate and readability of e-ETs and v-ETs post-insertion were
evaluated on farm conditions for a period of 1 year, biweekly until the
3rd month, and thereafter monthly until the 12th month. The study
was conducted on 197 lambs until the 12th month, because 183 male lambs
were sold at the end of 7 months. Electronic ear tag readings were performed
under static conditions in restrained animals using a hand-held transceiver
(Agrident APR500) with a built-in keyboard and integrated antenna. The
reader allows the introduction of birth records and official identification
number of the animal linked with the electronic identification code. Also,
each e-ET was read in dynamic conditions by using an ISO-compliant reader,
which was connected to a 94 × 52 cm frame antenna installed on a plastic
panel, which was able to read at a maximum distance of 100 cm for e-ETs. For
this purpose, the panel reader was mounted on the left side of a runway
(width 50 cm). When the animals passed in front of the antenna, an
electronic identification number appeared on the personal computer screen
and data from the panel reader were transmitted to the PC.
Performance of identification devices in lambs.
Electronic ear tags
Visual ear tags
Item
Overall
1/2
1/3
Overall
1/2
1/3
Birth to 7 months of age
Administered, n
380
190
190
380
190
190
Lost, n (%)
4 (1.1)
3 (1.6)
1 (0.5)
5 (1.3)
4 (2.1)
1 (0.5)
Electronic failures1, n (%)
0
0
0
–
–
–
Readable, n
376
187
189
375
186
189
Readability, %
98.9
98.4
99.5
98.7
97.9
99.5
DRE2, %
100
100
100
–
–
–
8–12 months of age
Previous3, n
197
93
104
197
93
104
Administered, n
0
0
0
0
0
0
Lost, n (%)
3 (1.5)
2 (2.2)
1 (1.0)
0
0
0
Electronic failures, n (%)
0
0
0
–
–
–
Readable, n
194
91
103
197
93
104
Readability, %
98.5
97.8
99.0
100
100
100
DRE, %
100
100
100
–
–
–
Birth to 12 months of age
Administered, n
197
93
104
197
93
104
Lost, n (%)
4 (2.0)
3 (3.2)
1 (1.0)
4 (2.0)
3 (3.2)
1 (1.0)
Electronic failures, n (%)
0
0
0
–
–
–
Readable, n
193
90
103
193
90
103
Readability, %
98.0
96.8
99.0
98.0
96.8
99.0
DRE, %
100
100
100
–
–
–
1 The number of unreadable transponder with electronic
readers; 2 dynamic reading efficiency (n read transponders/n readable
transponders × 100); 3 one hundred eighty-three male lambs were sold at 7 months
of age.
An e-ET that was unreadable, but robust, was considered as electronic
failure. Both ear-tag types were also monitored for loss, damage (breakage,
signs of gnawing, etc.), and ear tissue reactions at each reading control.
Unreadable devices were due to either loss or device failure (Carne et al.,
2009). When tags were missing, the date was recorded and the animal was
re-tagged. The readability (R) and dynamic reading efficiency (DRE) of
ear tags were calculated using the following formulas: R (%) = (n
readable devices/n applied devices) × 100 (Caja et al., 2014); DRE
= (n read transponders/n readable transponders) × 100 (Caja et al.,
1999).
Statistical analysis
Performance of ear tags and placement site were analysed by means of the Cox
proportional hazard (Cox, 1972) procedure. Non-significant factors (gender,
birth type, and birth weight) were removed from the model. As previously
used by Carne et al. (2009), a non-parametric Kaplan–Meier survival
analysis and log-rank tests of equality across strata were performed to
assess the difference in survival times between the ear tags and placement
site. All analyses were performed in SAS (2005) and SPSS statistical
software (v.20).
Results and discussion
Results on the performance of e-ETs and v-ETs in lambs are presented in Table 1.
Electronic and visual ear tags displayed 98.9 and 98.7 % readability, respectively, in
static conditions on 380 animals at the end of 7 months. The
performances of ear tags are mainly dependent on their losses caused from
tag breakage or ear splitting (Caja et al., 2014). In total, four tag losses
(1.1 %) were recorded in e-ETs, which occurred in the second, third,
fourth, and seventh months after tagging. For v-ETs, all tag losses (five tags, 1.3 %)
were observed in the first month. Two e-ET losses occurred
because of ear splitting, while two e-ETs were pulled free from the ear due to
enlarged holes. Split ears were not observed for v-ET losses; however five cases
of loss were registered as damage to the flag piece of v-ETs. The difference
between the lost cases of e-ETs and v-ETs may be explained by factors such as
the size, shape, and type of material of the tag. As a consequence,
readability of e-ETs and v-ETs at 7 months was similar. Readability of e-ETs
and v-ETs almost reached the ≥ 99 % value recommended by the
International Committee for Animal Recording (ICAR) at the sixth month
after tagging (ICAR, 2012).
Kaplan–Meier survival distribution functions for (a) electronic
ear tags placed on the mid-point (straight line) and the first-quarter part (dotted line) of
the ear, for (b) visual ear tags placed on the mid-point (straight line) and the
first-quarter part (dotted line) of the ear, for (c) electronic (dotted line) and visual ear tags
(straight line) placed on the mid-point part (1/2) of the ear, and for (d) electronic (dotted line)
and visual ear tags (straight line) placed on the first-quarter part (1/3) of the ear
in lambs.
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Regarding the placement site, loss rate in e-ETs placed on the 1/2 and 1/3
part of the ear was 1.6 % (three tags) and 0.5 % (one tag), respectively.
Visual ear tag loss rates were 2.1 % (four tags) for the 1/2 part and 0.5 %
(1 tag) for the 1/3 part of the ear. No statistically significant difference
between the loss rates based on ear-tag types and placement site was found.
Readability of ear tags (98.4 % for e-ETs, 97.9 % for v-ETs, 96.3 %
overall) placed on the 1/2 part of the ear did not reach the ICAR value,
whereas ear tags placed on the 1/3 part of the ear had readabilities of ≥ 99 % at 6 months after tagging as recommended by ICAR. Thomas et
al. (2006) reported that the overall loss of e-ETs was 9.9 % for sheep in
4.5 months and 19.2 % for lambs in about 3 months, and these lost
rates were unacceptably high for official use. Electronic and visual ear tag
losses observed in the study were lower than those reported in the
literature (Caja et al., 1999; Conill et al., 2002; Rusk, 2002; Ghirardi et
al., 2006; Thomas et al., 2006).
An electronic failure was not registered during this study. Thomas et al. (2006)
stated an electronic failure of 0.39 % in five types of e-ETs in
ewes. In addition to losses and failures, low dynamic reading efficiency is
one of the main problems for e-ETs (Huber, 2004). No reading failures in
dynamic conditions with the panel reader used in the runway were recorded,
which resulted in 100 % of DRE in the duration of the whole study. This
value was similar to those values reported by Abecia and Palacin (2014) and
Ait-Saidi (2014) for electronically identified ewes.
Three additional e-ETs were lost (1.5 %) on 197 lambs between 8 and 12 months
of age, which occurred in the 10th (two tags) and the 11th (one tag)
months after tagging. The increased e-ET losses could be the result of the
ear tags' high weight and thick pin causing the enlargement of the ear hole.
Electronic ear tag loss rates were 2.2 % (two tags) for the 1/2 part and 1.0 %
(one tag) for the 1/3 part of the ear. No v-ET losses were observed during
this period. The difference between the readability of e-ETs and v-ETs
(98.5 and 100 %, respectively) was not significant (P>0.05). However, Carne et al. (2009) found that button–button and flag–button
type e-ET had a significantly higher readability (100 and
100 %) than different v-ET types (82.9 and 94.0 %) at 6–12 months of age in dairy goats.
To evaluate the performance of e-ETs and v-ETs during the 1-year period,
data on 197 lambs, which were kept until the end of the study, were used
(Table 1). Electronic and visual ear tags showed 98.0 and 98.0 %
readability, respectively, in static conditions within the 12 months. By the end of the
year, four tag losses (2.0 %) were recorded in both ear-tag types.
Readability of e-ETs and v-ETs fulfilled the 98 % value required by ICAR
for official use at the end of the 1-year period after tagging (ICAR, 2012).
Loss rates in e-ETs and v-ETs placed on the 1/2 and 1/3 part of the ear were
3.2 % (three tags) and 1.0 % (1 tag), respectively, for both ear-tag types.
No significant differences (P>0.05) were observed between
placement site losses. Readability of ear tags (96.8 % for e-ETs and v-ETs,
93.5 % overall) placed on the 1/2 part of the ear did not reach the ICAR
value, whereas readability of ear tags placed on the 1/3 part of the ear was
99.0 % for e-ETs and v-ETs, and 98.1 % overall at 1 year after tagging
as recommended by ICAR. Ghirardi et al. (2006) observed a 3.3 % annual
loss in plastic ear tags in sheep. Carne et al. (2010) also reported 4.3 %
of e-ETs and 3.0 % of v-ET losses at 1 year in dairy goats, which was
unsatisfactory for official use according to the ICAR requirements.
Results obtained with the Kaplan–Meier nonparametric survival analyses are
displayed in Fig. 2 for e-ETs (a) and v-ETs (b) based on the ear-tag
placement site. When the survival distribution of e-ETs on 380 lambs between
birth and 12 months of age was compared based on the ear-tag placement site,
it was observed that losses of e-ETs placed on the 1/2 part of the ear
occurred in the 2nd, 4th, 7th, 10th, and 11th months
after tagging. On the other hand, losses of e-ETs placed on the 1/3 part of
the ear were observed in the 3rd and 10th months. Thus, retention
rates of e-ETs placed on the mid-point (1/2) and the first-quarter part (1/3)
of the ear were estimated as 97.4 and 98.9 %, respectively, at 12 months of age by
the Kaplan–Meier method.
Regarding with results of the Kaplan–Meier nonparametric survival analyses
for v-ETs, it can be observed in Fig. 2b that all losses of v-ETs placed on the
1/2 and 1/3 part of the ear occurred in the first month after tagging. Four
v-ETs were lost in the 1/2 part and one tag in the 1/3 part. Retention rates of
v-ETs placed on the mid-point (1/2) and the first-quarter part (1/3) of the
ear were estimated as 97.9 and 99.5 % at 12 months of age by the
Kaplan–Meier method.
Results of Kaplan–Meier nonparametric survival analyses according to ear-tag
type are displayed in Fig. 2 for the 1/2 part (c) and 1/3 part (d) of the
ear. In total, five e-ETs and four v-ETs placed on the 1/2 application site were
lost. Thus, retention rates of e-ETs and v-ETs placed on the mid-point (1/2)
of the ear was estimated as 97.4 and 97.9 %, respectively, at 12 months of age by the
Kaplan–Meier method.
As can be observed in Fig. 2d, two e-ETs and one v-ET placed on the 1/3 part of the
ear were lost. Thus, retention rates of e-ETs and v-ETs placed on the first-quarter part (1/3) of the ear was estimated as 98.9 and 99.5 %, respectively, at 12 months
of age by the Kaplan–Meier method. Kaplan–Meier
retention values estimated from censored data were either close to or higher
than the actual retention values. However, Carne et al. (2009) reported that
Kaplan–Meier-estimated readabilities were generally lower than actual
values for long-term retention of identification devices.