Assessment of Pain in Captive and Free-Ranging Ducks after Intra-Abdominal Transmitter Placement
Karen L. Machin, DVM, MSc
Department of Veterinary Physiological Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
Little information is available on avian pain perception, but it is generally accepted that birds are able to feel pain.2,5,8,9 Often analgesics may be withheld because the presence and severity of pain is not recognized. In small animals, our familiarity and close relationship with these animals often facilitates the recognition of pain. In addition, veterinarians are less familiar with the normal behavior of waterfowl and prey animals may be less likely to display overt pain-associated behavior.3 In comparison to pet species, wild avian species do not respond positively to human contact. It is therefore necessary to devise different methods of assessing pain in these species.
Free-ranging waterfowl are captured routinely to gain information about their biology and physiology. Often studies rely on radiotelemetry because it provides excellent information on movements, behavior and survival. Intra-abdominal transmitters provide more reliable data than externally mounted transmitters, but surgery is required for radio transmitter placement.6,7,10,12,15-17 Pain from surgery or direct pressure from intra-abdominal radio transmitters may alter behavior and decrease food intake, which may result in lowered reproductive success. Garrettson found that blue-winged teal (Anas discors) recovering from intra-abdominal radio transmitter surgery had progressive weight loss over 1 week.4 Pain may also alter the normal responses of a bird to its environment, which may increase susceptibility to predation. Behavioral changes may lead to disruption of pair bonds, alter nest site choice or reproductive success. Modification of normal behavior may result in erroneous interpretation of data if unrecognized subtle changes occur in the physiology, behavior, or well-being of the bird.10
Short holding times are beneficial to reduce stress, prevent pair bond disruption, or reduce detrimental effects of egg cooling when females are not incubating. Non-sedative analgesia is desirable since suitable conditions for safe recovery may be impossible to provide11; therefore, research is directed at nonsteroidal anti-inflammatory drugs (NSAIDs) and local anesthetics. Administration of analgesics prior to surgery reduces pain experienced by an animal more effectively than if the analgesic had been administered post-operatively.14 Therefore, a single pre-emptive dose may provide adequate analgesia following intra-abdominal transmitter placement.
To determine efficacy of a NSAID, ketoprofen, a sham surgery for implanting radio transmitters was done in captive mallard ducks (Anas platyrhynchos). Groups of two ducks (one male and one female) were chosen randomly to have either an incision (surgery) and ketoprofen (0.5, 1, 2, 5, 7.5 or 10 mg/kg) or no surgery (control) and an equal volume of saline. One male and one female mallard received each dose and treatment, and control animals were randomized completely. Two ducks were anesthetized with isoflurane simultaneously to allow birds to recover at the same time. Surgery involved a skin and muscle incision on the ventral abdomen to mimic placement of an intra-abdominal transmitter and tissues were closed with 4-0 absorbable suture.
Ducks were acclimatized to the pen for 3 days prior to the experiment and postoperatively birds were returned to the same pen as soon as possible after recovery. All birds were monitored using video recording for 24 hours prior to the experiment (control) and 48 hours postoperatively. Time spent performing various behaviors including comfort movements (stretching, flapping wings, preening, etc.), preening of surgical site, resting, swimming, standing, walking and feeding were recorded. Birds were assessed at 6 hours and daily for 7 days postoperatively. Body weight, incision site, hydration status and flight distance were assessed at 24, 48, 72 and 168 hours. Flight distance was defined as the distance between the observer and duck when the duck moved as the observer entered the room. All birds were euthanatized 7 days after surgery and a complete necropsy and histologic examination was performed to ensure that no gastrointestinal or renal damage occurred. Histology results will not be discussed here. Seventy hours of video tape for each group was viewed as 4-hour videotape segments which were chosen and viewed randomly by an observer blind to the treatments. Behaviors (listed above) were recorded at 30-second intervals. Data were analyzed using a change-point test and repeated-measures ANOVA.
All ducks stood, appeared active and clinically normal when observers entered the room. Flight distance could not be assessed as ducks stood against the far wall before they could be visualized. Palpation of the surgical site did not elicit wound guarding behavior or vocalizations, and all birds struggled during handling. Preliminary results revealed that at lower doses of ketoprofen (0.5–2.0 mg/kg), the most useful index of pain following surgery was reduced locomotion (walking, swimming) and time spent resting in a sitting position was increased. Preening of the ventral abdomen (surgical site) increased in all ducks but the control group. This may have been because feathers were removed from the surgical site or a true response to inflammation. Comparisons made by videotaping pre- and postoperatively were more effective for determining responses to pain than physical examination or observations done while observers were in the room. Conclusions about the effective dose of ketoprofen must be drawn with caution. Captive and field studies are ongoing to further define an effective dose for ketoprofen. No gross lesions were visible on necropsy. In addition, evaluation of pathologic effects must be completed to ensure safety when using single doses.
As part of another study, the efficacy of a local anesthetic (bupivacaine) was investigated using male ruddy ducks (Oxyura jamaicensis) implanted with 18–20 g radio transmitters. The research was conducted near Minnedosa, Manitoba (50°10′N, 99°47′W). Forty male ruddy ducks were divided randomly into one of two groups: (a) leg banded only and (b) surgical implantation of an intra-abdominal radio transmitter during propofol anesthesia.13 Birds that had surgery had 2.0 mg/kg of bupivacaine injected into the surgical site prior to surgery. Ducks were observed, through a spotting scope, 6 hours postoperatively for 20 minutes. Aspects of behavior were recorded as comfort movements (stretching, flapping wings, preening), preening of surgical site, resting in cover or in the open, swimming, foraging and out of sight every 30 seconds. Data were analyzed using a multivariate analysis of variance (MANOVA) to control simultaneously for several dependent behavior variables. Univariate ANOVAs were used to identify which aspects of behavior were significant. Results were considered significant at p<0.05.
Nineteen ducks that had surgery were easily located because they were resting motionless on floating vegetation or land, and had a puffed up appearance. One implanted male was killed by a red-tailed hawk (Buteo jamaicensis) approximately 6 hours after surgery. Males with leg bands only were more difficult to locate and only 8 ducks in this control group were observed. There was an overall significant difference in behavior between implanted and leg banded-only ducks (MANOVA, df=6,24, p=0.035). Implanted males spent significantly less time feeding and swimming and more time resting in the open than leg banded-only males (univariate ANOVA, df=1,29, p=0.001, 0.013 and 0.002, respectively). In contrast, leg banded-only males spent more time out of sight, as they were difficult to locate, and when resting, spent less time in the open. In addition, a female ruddy duck (as part of a different study), recaptured 5 days after surgery, had a weight loss of 50 g. Ruddy ducks are adapted highly to their aquatic lifestyle and resting on land is considered an unusual behavior.1 Results from this study suggest that the surgical procedure produced discomfort and abnormal behavior postoperatively which may also make ducks more susceptible to predation. Local anesthesia using bupivacaine at the dosage in this study is likely not adequate for pain control after surgical placement of intra-abdominal transmitters. Secondary inflammatory effects may contribute to altered behavior in ruddy ducks and weight loss seen in the female ruddy duck.
Evaluation of responses of captive wild ducks was best done through videotaping. In the field, ducks showed similar behavioral responses to a painful procedure as captive ducks. A knowledge of normal time budgets and diurnal behavior for the species is also important. Additional experiments are needed to further characterize behavioral changes associated with pain in waterfowl and evaluate pre-emptive analgesic efficacy.
This research was supported by the Canadian Wildlife Service, Delta Waterfowl Foundation, Ducks Unlimited Institute for Wetland and Waterfowl Research, and the Wildlife Health Fund, University of Saskatchewan. I would also like to thank my supervisor Dr. Alex Livingston and Dr. Robert Brua for their assistance in writing this abstract. Special thanks to Marnie Cooper and Lise Tellier for technical support during these studies.
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