Abstract
The anesthesia of aoudads (Ammotragus lervia) in an exhibit at Tierpark Hagenbeck in Hamburg, Germany was compared to a group of free-ranging aoudads at the Wildlife Safari in Winston, Oregon, USA. Both methods of immobilization (xylazine-ketamine in Hamburg and xylazine-tiletamine-zolazepam in Winston) achieved a smooth induction and a very good immobilization. The reversal was carried out with a combination of yohimbine and atipamezole in Hamburg and only atipamezole in Winston. Both methods deliver a smooth recovery and enable the animal to be released into the herd within a few hours.
Introduction
Institution A: Tierpark Hagenbeck, Hamburg, Germany
Tierpark Hagenbeck in Hamburg has kept barbary sheep for many years. In general, approximately 25 animals are kept in a 300 m2 fenced-in area with a flooring of natural rock including climbing structures. Immobilizations are done on a regular basis, mainly for physical examinations, medical procedures, or transports to other institutions.
Institution B: Wildlife Safari Winston, Oregon, USA
Wildlife Safari keeps a large group of aoudads (about 40 animals) free-ranging in a drive-through area of 170 m2, together with bison (Bison bison bison), alpaca (Lama pacos), mustangs (Equus caballus), and wapiti elk (Cervus elaphus nelsoni). The soil consists mainly of clay and the heavily wooded area contains ponds as well. The only solid structures are the drive-through paths for the vehicles which are randomly used by the aoudads.
The weather in Winston has more extremities as compared to Hamburg with its temperate climate with warm summers and mild cloudy winters. Hot summers and wet moderate winters are common in this region. Because of the high precipitation during the winter in Western Oregon the soil has a very soft consistency and the hooves cannot find the necessary abrasion. Massive overgrowth of the foot horn causes lameness and sometimes osteomyelitis. Therefore, all animals are annually anesthetized for hoof trims and general examinations.
The anesthetic agent xylazine (2(2,6-dimethylphenylamino)-4-H-5,6-dihydro-1,3-thiazine hydrochloride) stimulates the α2-receptors of the central nervous system and, therefore, inhibits the release of adrenaline and serotonine. In sufficient doses the sedative provides central muscle relaxation and analgesia.1 Often xylazine is used in combination with ketamine hydrochloride (2-(o-chlorophenyl)-2-methylamino cyclohexanone hydrochloride). Ketamine belongs to the dissociative anesthetic agents and produces catalepsia and analgesia.1 The combination of both drugs achieved good results in ruminants.2,8 Another possibility is the combination of an α2-agonist with tiletamine and zolazepam (Telazol [tiletamine hydrochloride and zolazepam hydrochloride]). Tiletamine is a dissociative agent that is comparable but more effective than ketamine. Zolazepam is a Pyrazolodiazepinone and has been used as a tranquillizer and anticonvulsant. The combination of tiletamine and zolazepam (TZ) has been widely used to immobilize wild animals.3,6 To reduce the amount of TZ and decrease the risks of convulsion and excitation xylazine was added to the drug combination with good results.7 The sedative effect of xylazine can be reversed with α2-adrenocepto antagonists yohimbine hydrochloride or atipamezole (4-(2-ethyl-2,3-dihydro-1H-inden-2-yl)-1H-imidazole hydrochloride).4 Here both methods of immobilization are compared.
Material and Methods
In Hamburg 31 aoudads were immobilized with a combination of xylazine and ketamine. 500 mg xylazine (Rompun® Dry Substance, Bayer) was mixed with 5 ml ketamine hydrochloride (Ketavet®, Pharmacia and Upjohn, 100 mg/ml) to receive a concentration of 100 mg xylazine and 100 mg ketamine per ml. The dosage was set up according to the age and appearance of the animal and the drugs were administered into the thigh muscles via dart delivered with a blowpipe. The body weight was estimated as <25 kg in the animals up to 1 year of age, 25–40 kg for animals aged up to 4 years and 50 kg (females) and 80–90 kg (males) for adults over the age of 4 years. The induction time was measured from the time when the dart hit the animal until the aoudad became recumbent. The animal was then positioned in right lateral recumbency. In four animals a pulse oximetry probe was placed on the tongue or one of the ears and the pulse (beats/m) and the hemoglobin saturation (SpO2) were recorded. During the anesthesia, blood was drawn from the jugular vein, injected into an EDTA-tube and a serum tube and sent off to a laboratory. After the procedure the anesthetic agents were antagonized with 1 ml yohimbine (Yohimbin-HCl 1%)/20 kg BW and 1 ml atipamezole (Atipamezolehydrochloride, Antisedan®, Pfizer, 5 mg/ml)/50 kg BW. The time between the injection and animal standing for the first time was recorded.
In Winston, aoudads have been anesthetized with a combination of xylazine, tiletamine, and zolazepam. The body weight of the animal was estimated and the drugs were administered into the thigh muscles via dart (Pneudart®) delivered with a rifle (Dan-inject®). The dose used was 1.1 mg Telazol/kg BW and 1.0 mg xylazine/kg BW.
Five 1-year-old females weighed between 27 and 36 kg. One male weighed 57 kg. Two 1–2-year-old female animals weighed 57 and 68 kg, and two males of the same age group weighed 77–82 kg. Three female 2–4-year-olds weighed 45–80 kg and five males weighed 77–114 kg. The body weight of the three over 4-year-old adult female aoudads ranged from 57 to 68 kg and the 2.0 males weight 90 and 136 kg. The induction time was measured from the time when the dart hit the animal until the aoudad became recumbent or was found recumbent after being out-of-sight. Prior to the antagonism of the anesthetic agents the animal was placed in a wooden crate. 1 mg Atipamezole (Antipamezolhydrochloride, Antisedan®, Pfizer, 5 mg/ml) for every 10 mg of xylazine was injected intravenously and the catheter was removed. The time from reversal until the animal became sternal was recorded.
Results
Four adult female animals were connected to the pulse oximeter. It showed average values of 81.5% SpO2 and 72.5 bpm of pulse.
A reference list of hematologic and biochemical data of 7.7 animals aged 4–8 months and 2.0 adult aoudads in Winston and Hamburg are given in Tables 1, 2, and 3.
Table 1. Institution A in Hamburg
|
Sex ratio
|
Age
|
Mean dosage
(mg/animal)a,b
|
Average onset of anesthesia
(minutes after darting)
|
Average procedure length
(= antidote given)
|
Antidote (ml)c,d
|
Animal stands
(minutes post antagonization)
(PA)
|
|
0.1
|
3 months
|
5 mg X +
25 mg K
|
8 minutes
|
41 minutes
|
0.5 Yo IM
0.1 At IV
|
10 minutes PA
|
|
3.4
|
4.5–7 months
|
22.4 mg X +
51.43 mg K
|
12.14 minutes
|
31.29 minutes
|
0.93 Yo IM
0.33 At IV
|
1.86 minutes PA
|
|
1.2.0
|
8 months
|
36.25 mg X +
165 mg K
|
10 minutes
|
41.25 minutes
|
1.13 Yo IM
0.41 At IV
|
5.75 minutes PA
|
|
3.6
|
1 year
|
40 mg X +
164.44 mg K
|
9.33 minutes
|
32.56 minutes
|
1.94 Yo IM
0.52 At IV
|
13 minutes PA
|
|
1.3
|
2–3 years
|
45 mg X +
160 mg K
|
8.75 minutes
|
49.5 minutes
|
2.5 Yo IM
0.68 At IV
|
10.25 minutes PA
|
|
0.3
|
4 years
|
50 mg X +
200 mg K
|
14.67 minutes
|
33 minutes
|
3.67 Yo IM
1.17 At IV
|
9 minutes PA
|
|
2.1
|
>4 years
|
80 mg X +
253.33 mg K
|
15.33 minutes
|
41.33 minutes
|
4 Yo IM
1.93 At IV
|
6 minutes PA
|
aX=xylazine
bK=ketamine
cYo=Yohimbine
dAt=Atipamezole
Table 2. Institution B in Winston
|
Sex ratio
|
Age
|
Mean dosage (mg/kg body weight)a,b
|
Average onset of anesthesia after darting
|
Atipamezole (mg)
(mg/kg body weight)
|
Animal sternal/stands (minutes post antagonization)
(PA)
|
|
0.5
|
1 year
|
60 mg T + 59 mg X
1.82 mg T + 1.79 mg X
|
6.6 minutes
|
6 mg
0.18 mg/kg
|
2.2 minutes PA
|
|
1.0
|
1 year
|
75 mg T + 75 mg X
1.32 mg T + 1.32 mg X
|
4 minutes
|
7.5 mg
0.13 mg/kg
|
1 minutes PA
|
|
0.2
|
1–2 years
|
75 mg T + 70 mg X
1.21 mg T + 1.13 mg X
|
7.5 minutes
|
7 mg
0.11 mg/kg
|
1.5 minutes PA
|
|
2.0
|
1–2 years
|
100 mg T + 95 mg X
1.8 mg T + 2.49 mg X
|
7.5 minutes
|
9.5 mg
0.17 mg/kg
|
1.5 minutes PA
|
|
0.3
|
2–4 years
|
75 mg T + 70 mg
1.26 mg T + 1.18 mg X
|
8.3 minutes
|
7 mg
0.12 mg/kg
|
2.33 minutes PA
|
|
5.0
|
2–4 years
|
90 mg T + 89 mg X
1.01 mg T + 1.0 mg X
|
7.4 minutes
|
8.76 mg
0.1 mg/kg
|
2.6 minutes PA
|
|
0.3
|
>4 years
|
83 mg T + 80 mg X
1.4 mg T + 1.32 mg X
|
8 minutes
|
8 mg
0.13 mg/kg
|
2.33 minutes PA
|
|
2.0
|
>4 years
|
75 mg T + 75 mg X
0.69 mg T + 0.65 mg X
|
10.5 minutes
|
7 mg
0.065 mg/kg
|
2 minutes PA
|
aT=Telazol
bX=Xylazine
Table 3. Biochemical data
|
Test
|
Mean
|
Minimum value
|
Maximum value
|
|
White blood cell count (x 109/L)
|
9.25
|
5.3
|
13.7
|
|
Red blood cell count (x 1012/L)
|
15.56
|
10.3
|
18.3
|
|
Hemoglobin (g/dl)
|
12.06
|
9.88
|
13.6
|
|
Hematocrit (%)
|
30.78
|
26.3
|
34.4
|
|
MCV (f/L)
|
20.16
|
16.4
|
27.8
|
|
MCH (pg/dl)
|
7.83
|
6.94
|
9.73
|
|
MCHC (g/dl)
|
39.18
|
35
|
42.6
|
|
Platelet count (x 109/L)
|
639
|
511
|
767
|
|
Segmented neutrophils (x 109/L)
|
6.04
|
2.85
|
10.32
|
|
Lymphocytes (x 109/L)
|
2.99
|
0.37
|
5.15
|
|
Monocytes (x 109/L)
|
0.10
|
0
|
0.41
|
|
Eosinophils (x 109/L)
|
0.08
|
0
|
0.37
|
|
Basophils (x 109/L)
|
0.01
|
0
|
0.07
|
|
Neutrophilic Bands (x 109/L)
|
0.03
|
0
|
0.24
|
|
Calcium (mMol/L)
|
2.25
|
1.62
|
2.57
|
|
Phosphorus (mMol/L)
|
2.69
|
2.07
|
3.57
|
|
Sodium (mMol/L)
|
144.5
|
139
|
149
|
|
Potassium (mMol/L)
|
4.37
|
3.5
|
4.86
|
|
Iron (umol/L)
|
17.85
|
13.5
|
22.9
|
|
Alkaline phosphatase (U/L)
|
271
|
78
|
634
|
|
Gamma glutamyltransferase (U/L)
|
56.63
|
32
|
175
|
|
Lactate dehydrogenase (U/L)
|
576.75
|
471
|
810
|
|
Aspartate aminotransferase (U/L)
|
131.75
|
75
|
327
|
|
Alanine aminotransferase (U/L)
|
64.44
|
44
|
98
|
|
Triglyceride (mg/dl)
|
25.31
|
5
|
74
|
|
Cholesterol (mg/dl)
|
133.88
|
60
|
227
|
|
Total bilirubin (mg/dl)
|
0.36
|
<0.2
|
0.36
|
|
Glucose (mg/dl)
|
169.63
|
89
|
262
|
|
Urea (mg/dl)
|
48.50
|
30
|
85
|
|
Creatinine (mg/dl)
|
1.52
|
1.21
|
3
|
|
Total protein (g/L)
|
58.98
|
47.7
|
69.9
|
Discussion
Inductions with both ketamine and xylazine (KX) and tiletamine, zolazepam, and xylazine (TZX) were rapid and smooth at both institutions. Immobilization with the combination of xylazine and ketamine and xylazine, tiletamine, and zolazepam has been reported as very efficient for ruminants in the literature for a long time. The effects of xylazine can be reversed with the α2- adrenoceptor antagonist yohimbine. The recommended dose for the antagonization is 0.125–0.25 mg/kg body weight intravenously or intramuscularly.5 In Hamburg, atipamezole was added to yohimbine and revealed better recoveries than in the past. In Winston, only atipamezole was given and provided smooth and rapid recoveries. Jalanka and Roeken4 reported on the successful use of atipamezole as a reversal for xylazine in a dose of 1 mg of atipamezole for every 8–12 mg of xylazine used.
Conclusion
The comparison of anesthesias in both institutions led to the conclusion that both drug combinations are a valuable method to induce and maintain a safe immobilization in barbary sheep. The recovery with either yohimbine + atipamezole or only atipamezole showed no significant differences, therefore the use of yohimbine in combination with atipamezole apparently does not increase the efficiency.
Literature Cited
1. Fritsch R. Allgemeine Pharmakologische und Klinische Grundlagen der Immobilisation. DVG Tagung Tierpark Hellabrunn München. 1990:13–26.
2. Gray CW, Bush M, Beck CC. Clinical experience using C1744 in chemical restraint of exotic specimens. J Zoo Anim Med. 1974;5:12–21.
3. Hugues F, Leclerc-Cassan M, Marc JR. Anesthésie des animaux non domestiques, essai d´un nouvel anesthésique. L`Association Tiletamin/Zolazepam (Zoletil.N.I.). Rec Med Vet. 1986;162(3):427–431.
4. Jalanka HH, Roeken BO. The use of medetomidine, medetomidine-ketamine combinations, and atipamezole in nondomestic mammals: A review. J Zoo Wildl Med. 1990;21:259–282.
5. Jalanka HH. Medetomidine, medetomidine-ketamine combinations and atipamezole in nondomestic mammals: A clinical, physiological and comparative study. Academic dissertation, Department of Clinical Sciences, College of Veterinary Medicine. Helsinki, Finland. 1991.
6. Schobert E. Telazol-Use in wild and exotic animals. Vet Med. 1987;82(10):1080–1088.
7. Thurmon JC, Lin HC, Benson GJ, Tranquilli AW, Olson WA. Combining telazol and xylazine for anaesthesia in calves. Vet Med. 1989;84(8):824–829.
8. Wiesner H. Zur Neuroleptanalgesie bei Zootieren und Gatterwild unter Anwendung des Telinject Systems. Kleintierpraxis. 1975;20:18–24.