Ngaio J. Beausoleil

Introducing breathlessness as a significant animal welfare issue

Abstract Breathlessness is a negative affective experience relating to respiration, the animal welfare significance of which has largely been underestimated in the veterinary and animal welfare sciences. In this review, we draw attention to the negative impact that breathlessness can have on the welfare of individual animals and to the wide range of situations in which mammals may experience breathlessness. At least three qualitatively distinct sensations of breathlessness are recognised in human medicine – respiratory effort, air hunger and chest tightness – and each of these reflects comparison by cerebral cortical processing of some combination of heightened ventilatory drive and/or impaired respiratory function. Each one occurs in a variety of pathological conditions and other situations, and more than one may be experienced simultaneously or in succession. However, the three qualities vary in terms of their unpleasantness, with air hunger reported to be the most unpleasant. We emphasise the important interplay among various primary stimuli to breathlessness and other physiological and pathophysiological conditions, as well as animal management practices. For example, asphyxia/drowning of healthy mammals or killing those with respiratory disease using gases containing high carbon dioxide tensions is likely to lead to severe air hunger, while brachycephalic obstructive airway syndrome in modern dog and cat breeds increases respiratory effort at rest and likely leads to air hunger during exertion. Using this information as a guide, we encourage animal welfare scientists, veterinarians, laboratory scientists, regulatory bodies and others involved in evaluations of animal welfare to consider whether or not breathlessness contributes to any compromise they may observe or wish to avoid or mitigate.

Advantages and limitations of the Five Domains model for assessing welfare impacts associated with vertebrate pest control

Abstract Many pest control activities have the potential to impact negatively on the welfare of animals, and animal welfare is an important consideration in the development, implementation and evaluation of ethically defensible vertebrate pest control. Thus, reliable and accurate methods for assessing welfare impacts are required. The Five Domains model provides a systematic method for identifying potential or actual welfare impacts associated with an event or situation in four physical or functional domains (nutrition, environment, health or functional status, behaviour) and one mental domain (overall mental or affective state). Here we evaluate the advantages and limitations of the Five Domains model for this purpose and illustrate them using specific examples from a recent assessment of the welfare impacts of poisons used to lethally control possums in New Zealand. The model has a number of advantages which include the following: the systematic identification of a wide range of impacts associated with a variety of control tools; the production of relative rankings of tools in terms of their welfare impacts; the easy incorporation of new information into assessments; and the highlighting of additional information needed. For example, a recent analysis of sodium fluoroacetate (1080) poisoning in possums revealed the need for more information on the period from the onset of clinical signs to the point at which consciousness is lost, as well as on the level of consciousness during or after the occurrence of muscle spasms and seizures. The model is also valuable because it clearly separates physical or functional and affective impacts, encourages more comprehensive consideration of negative affective experiences than has occurred in the past, and allows development and evaluation of targeted mitigation strategies. Caution must be used in interpreting and applying the outputs of the model, most importantly because relative rankings or grades are fundamentally qualitative in nature. Certain domains are more useful for evaluating impacts associated with slower/longer-acting tools than for faster-acting methods, and it may be easier to identify impacts in some domains than others. Overall, we conclude that the Five Domains model advances evaluation of the animal welfare impacts of vertebrate pest control methods, provided users are cognisant of its limitations.

Does direct human eye contact function as a warning cue for domestic sheep (Ovis aries)

Direct eye contact may function as a warning cue during interspecific interactions, and human staring has been shown to influence the behavior of many species. The authors used an arena test to assess whether human staring altered the behavior of domestic sheep (Ovis aries) compared with no human eye contact. Sheep glanced at the staring humans face more often in the first 2 min of the test, indicating that they perceived a difference between the human stimuli. Staring also elicited more locomotor activity and urination than averted gaze. However, there were no differences in fear-related behaviors, suggesting that a staring human did not represent a greater immediate threat than a nonwatching human. These results imply that human staring is a warning cue for domestic sheep, but no more. Without further reinforcement, sheep quickly habituated to the warning cue.

Lambs show changes in ear posture when experiencing pain

Ear posture, or the frequency of postural changes, may reflect various emotional states of animals. In adult sheep (Ovis aries), the ‘forward’ ear posture has been associated with negative experiences whereas the ‘plane’ posture has been associated with positive ones. This study aimed to see whether ear postures related to the experience of pain in lambs. The ear behaviour of four to eight week-old lambs (n = 44) was measured before and after tail-docking using a rubber ring. Each lamb was docked and its behaviour recorded while in the company of an observer lamb of similar age; each acted once as focal (docked) lamb and once as observer within the same pair. Lambs were docked in one of two rounds, so that half were docked in their first exposure to the test environment and half in their second exposure. Tail-docking was associated with an increase in the proportion of time spent with ears backward and decreases in the proportion of time spent with ears plane and forward (mean [± SEM]: Backward: pre 0.12 [± 0.04], post 0.56 [± 0.04]; Plane: pre 0.55 [± 0.05], post 0.19 [± 0.05]; Forward: pre 0.27 [± 0.04], post 0.18 [± 0.04]). There was also a significant increase in the number of changes between ear postures after docking (pre 5.63 [± 0.66], post 9.11 [± 0.66]). Over both periods, female lambs held their ears asymmetrically for longer than males (mean of ranks [± SEM] [raw proportion of time]: Females 52.14 [± 3.44] [0.09 (± 0.01)], males 37.54 [± 3.40] [0.05 (± 0.01)]). This is the first study to demonstrate changes in the ear posture of lambs associated with the negative experience of pain. Ear posture is a non-invasive indicator of physical pain in lambs and may be useful for evaluating potential welfare compromise.

A systematic approach to evaluating and ranking the relative animal welfare impacts of wildlife control methods: poisons used for lethal control of brushtail possums (Trichosurus vulpecula) in New Zealand

Abstract Context. Control of unwanted wildlife (‘pest’ animals) is undertaken for conservation and economic reasons, and when such animals are considered a nuisance. Such control should be undertaken using approaches that minimise, as far as possible, detrimental impacts on the welfare of the animals. Using a scientific framework based on the Five Domains model, the relative welfare impacts of pest control methods can be compared across methods and pest species. Aims. We demonstrate the application of a modified version of this framework to evaluate the relative impacts of seven Vertebrate Toxic Agents (VTAs) used to control brushtail possums (Trichosurus vulpecula) in New Zealand. The evaluation is used to produce a ranking of the seven VTAs based on their relative impacts on possum welfare. Methods. Scientific literature describing mode of toxic action, specific effects in possums or other animals and reports from human poisonings was collated as reference material for a panel of six experts. The panel produced a median welfare impact score (‘none’ to ‘extreme’) for each of the Five Domains. The ‘Overall Grade’ (1 to 8) reflected the intensity and duration of all impacts of a VTA on possums. Key results. All VTAs evaluated have at least moderate impacts on possum welfare, lasting for at least minutes. Cyanide was assessed as having the lowest welfare impacts (median grade 4), and cholecalciferol and the anticoagulants the highest impacts (7.5 to 8). Zinc phosphide was assigned an intermediate grade (6) with high confidence. While the overall impacts of sodium fluoroacetate (1080) and phosphorus were also assessed as intermediate (6), the panel’s confidence in these scores was low. Conclusions. From an animal welfare perspective, anticoagulant poisons and cholecalciferol should be the least preferred options for controlling possums in New Zealand, as VTAs with less severe welfare impacts are available. Implications. The results of such assessments allow animal welfare impacts to be integrated with other factors in wildlife management decision-making and policy development, and are thus useful for managers, researchers, regulators and operators. Evaluation of welfare impacts aligns with the goals and mandates of ethical wildlife control and may also be valuable in wider wildlife research and management activities.

Comparison of neural histomorphology in tail tips from pigs docked using clippers or cautery iron

Tail docking of pigs is commonly performed to reduce the incidence of unwanted tail-biting behaviour. Two docking methods are commonly used: blunt trauma cutting (i.e. using side clippers), or cutting and concurrent cauterisation using a hot cautery iron. A potential consequence of tail amputation is the development of neuromas at the docking site. Neuromas have been linked to neuropathic pain, which can influence the longer-term welfare of affected individuals. To determine whether method of tail docking influences the extent of neuroma formation, 75 pigs were allocated to one of three treatments at birth: tail docked using clippers; tail docked using cautery iron; tail left intact. Tail docking was performed at 2 days of age and pigs were kept under conventional conditions until slaughter at 21 weeks of age. Tails were removed following slaughter and subjected to histological examination. Nerve histomorphology was scored according to the following scale: 1=discrete well-organised nerve bundles; 2=moderate neural proliferation and disorganisation affecting more than half of the circumference of the tail; 3=marked neural proliferation to form almost continuous disorganised bundles or non-continuous enlarged bundles compressing the surrounding connective tissue. Scores of 2 or 3 indicated neuroma formation. Scores were higher in docked pigs than undocked pigs (P<0.001), but did not differ between pigs docked using clippers and those docked using cautery (P=0.23). The results indicate that tail docking using either clippers or cautery results in neuroma formation, thus having the potential to affect long-term pig welfare.

Effects of isoflurane, sevoflurane and methoxyflurane on the electroencephalogram of the chicken

OBJECTIVE Anaesthetics have differing effects on mammalian electroencephalogram (EEG) but little is known about the effects on avian EEG. This study explored how inhalant anaesthetics affect chicken EEG. STUDY DESIGN Experimental study. ANIMALS Twelve female Hyline Brown chickens aged 6-11 weeks. METHODS Each chicken was anaesthetized with isoflurane, sevoflurane, and methoxyflurane. For each, anaesthesia was adjusted to 1, 1.5 and 2 times Minimum Anaesthetic Concentration (MAC). Total Power (Ptot), Median Frequency (F50), Spectral Edge Frequency (F95) and Burst Suppression Ratio (BSR) were calculated at each volume concentration. BSR data were analyzed using doubly repeated measures anova. Neither isoflurane nor sevoflurane could be included in analysis of F50, F95 and Ptot because of extensive burst suppression; Methoxyflurane data were analyzed using RM anova. RESULTS There was a significant interaction between anaesthetic and concentration on BSR [F(4,22) = 10.65, p < 0.0001]. For both isoflurane and sevoflurane, BSR increased with concentration. Isoflurane caused less suppression than sevoflurane at 1.5 MAC and at final 1 MAC while methoxyflurane caused virtually no burst suppression. Methoxyflurane concentration had a significant effect on F50 [F(2,20) = 3.83, p = 0.04], F95 [F(2,20) = 4.03, p = 0.03] and Ptot [F(2,20) = 5.22, p = 0.02]. Decreasing methoxyflurane from 2 to 1 MAC increased F50 and F95. Ptot increased when concentration decreased from 1.5 to 1 MAC and tended to be higher at 1 MAC than at 2 MAC. CONCLUSIONS AND CLINICAL RELEVANCE Isoflurane and sevoflurane suppressed chicken EEG in a dose-dependent manner. Higher concentrations of methoxyflurane caused an increasing degree of synchronization of EEG. Isoflurane and sevoflurane suppressed EEG activity to a greater extent than did methoxyflurane at equivalent MAC multiples. Isoflurane caused less suppression than sevoflurane at intermediate concentrations. These results indicate the similarity between avian and mammalian EEG responses to inhalant anaesthetics and reinforce the difference between MAC and anaesthetic effects on brain activity in birds.

Effects of halothane on the electroencephalogram of the chicken

Abstract Little is known about the effects of inhalant anaesthetics on the avian electroencephalogram (EEG). The effects of halothane on the avian EEG are of interest, as this agent has been widely used to study nociception and analgesia in mammals. The objective of this study was to characterize the effects of halothane anaesthesia on the EEG of the chicken. Twelve female Hyline Brown chickens aged 8–10 weeks were anaesthetized with halothane in oxygen. For each bird, anaesthesia was progressively increased from 1–1.5 to 2 times the Minimum Anesthetic Concentration (MAC), then progressively decreased again. At each concentration, a sample of EEG was recorded after a 10‐min stabilization period. The mean Total Power (PTOT), Median Frequency (F50) and 95% Spectral Edge Frequency (F95) were calculated at each halothane MAC, along with the Burst Suppression Ratio (BSR). Burst suppression was rare and BSR did not differ between halothane concentrations. Increasing halothane concentration from 1 to 2 MAC resulted in a decrease in F50 and increase in PTOT, while F95 increased when MAC was reduced from 1.5 to 1. The results indicate dose‐dependent spectral EEG changes consistent with deepening anaesthesia in response to increasing halothane MAC. As burst suppression was rare, even at 1.5 or 2 times MAC, halothane may be a suitable anaesthetic agent for use in future studies exploring EEG activity in anaesthetized birds.

Equine Welfare during Exercise: An Evaluation of Breathing, Breathlessness and Bridles

Simple Summary Horses have superior athletic capabilities due largely to their exceptional cardiorespiratory responses during exercise. This has particular relevance to horses’ potential to experience breathlessness, especially when their athletic performance is reduced by impaired respiratory function. Breathlessness, incorporating three types of unpleasant experiences, has been noted as of significant animal welfare concern in other mammals. However, the potential for breathlessness to occur in horses as usually ridden wearing bitted bridles has not yet been evaluated in detail. Accordingly, key physiological responses to exercise and the consequences of impaired respiratory function are outlined. Then the physiological control of breathing and the generation of the aversive experiences of breathlessness are explained. Finally, the potential for horses with unimpaired and impaired respiratory function to experience the different types of breathlessness is evaluated. This information provides a basis for considering the circumstances in which breathlessness may have significant negative welfare impacts on horses as currently ridden wearing bitted bridles. Potential beneficial impacts on respiratory function of using bitless bridles are then discussed with emphasis on the underlying mechanisms and their relevance to breathlessness. It is noted that direct comparisons of cardiorespiratory responses to exercise in horses wearing bitless and bitted bridles are not available and it is recommended that such studies be undertaken. Abstract Horses engaged in strenuous exercise display physiological responses that approach the upper functional limits of key organ systems, in particular their cardiorespiratory systems. Maximum athletic performance is therefore vulnerable to factors that diminish these functional capacities, and such impairment might also lead to horses experiencing unpleasant respiratory sensations, i.e., breathlessness. The aim of this review is to use existing literature on equine cardiorespiratory physiology and athletic performance to evaluate the potential for various types of breathlessness to occur in exercising horses. In addition, we investigate the influence of management factors such as rein and bit use and of respiratory pathology on the likelihood and intensity of equine breathlessness occurring during exercise. In ridden horses, rein use that reduces the jowl angle, sometimes markedly, and conditions that partially obstruct the nasopharynx and/or larynx, impair airflow in the upper respiratory tract and lead to increased flow resistance. The associated upper airway pressure changes, transmitted to the lower airways, may have pathophysiological sequelae in the alveolae, which, in their turn, may increase airflow resistance in the lower airways and impede respiratory gas exchange. Other sequelae include decreases in respiratory minute volume and worsening of the hypoxaemia, hypercapnia and acidaemia commonly observed in healthy horses during strenuous exercise. These and other factors are implicated in the potential for ridden horses to experience three forms of breathlessness—”unpleasant respiratory effort”, “air hunger” and “chest tightness”—which arise when there is a mismatch between a heightened ventilatory drive and the adequacy of the respiratory response. It is not known to what extent, if at all, such mismatches would occur in strenuously exercising horses unhampered by low jowl angles or by pathophysiological changes at any level of the respiratory tract. However, different combinations of the three types of breathlessness seem much more likely to occur when pathophysiological conditions significantly reduce maximal athletic performance. Finally, most horses exhibit clear behavioural evidence of aversion to a bit in their mouths, varying from the bit being a mild irritant to very painful. This in itself is a significant animal welfare issue that should be addressed. A further major point is the potential for bits to disrupt the maintenance of negative pressure in the oropharynx, which apparently acts to prevent the soft palate from rising and obstructing the nasopharynx. The untoward respiratory outcomes and poor athletic performance due to this and other obstructions are well established, and suggest the potential for affected animals to experience significant intensities of breathlessness. Bitless bridle use may reduce or eliminate such effects. However, direct comparisons of the cardiorespiratory dynamics and the extent of any respiratory pathophysiology in horses wearing bitted and bitless bridles have not been conducted. Such studies would be helpful in confirming, or otherwise, the claimed potential benefits of bitless bridle use.

Assessment of a carbon dioxide laser for the measurement of thermal nociceptive thresholds following intramuscular administration of analgesic drugs in pain-free female cats

OBJECTIVE To assess the potential of a thermal carbon dioxide (CO2) laser to explore antinociception in pain-free cats. STUDY DESIGN Experimental, prospective, blinded, randomized study. ANIMALS Sixty healthy adult female cats with a (mean±standard deviation) weight of 3.3±0.6 kg. METHODS Cats were systematically allocated to one of six treatments: saline 0.2 mL per cat; morphine 0.5 mg kg(-1); buprenorphine 20 μg kg(-1); medetomidine 2 μg kg(-1); tramadol 2 mg kg(-1), and ketoprofen 2 mg kg(-1). Latency to respond to thermal stimulation was assessed at baseline and at intervals of 15-30, 30-45, 45-60, 60-75, 90-105 and 120-135 minutes. Thermal thresholds were assessed using time to respond behaviourally to stimulation with a 500 mW CO2 laser. Within-treatment differences in response latency were assessed using Friedmans test. Differences amongst treatments were assessed using independent Kruskal-Wallis tests. Where significant effects were identified, pairwise comparisons were conducted to elucidate the direction of the effect. RESULTS Cats treated with morphine (χ2=12.90, df=6, p=0.045) and tramadol (χ2=20.28, df=6, p=0.002) showed significant increases in latency to respond. However, subsequent pairwise comparisons indicated that differences in latencies at specific time-points were significant (p<0.05) only for tramadol at 60-75 and 90-105 minutes after administration (21.9 and 43.6 seconds, respectively) in comparison with baseline (11.0 seconds). No significant pairwise comparisons were found within the morphine treatment. Injections of saline, ketoprofen, medetomidine or buprenorphine showed no significant effect on latency to respond. CONCLUSIONS AND CLINICAL RELEVANCE The CO2 laser technique may have utility in the assessment of thermal nociceptive thresholds in pain-free cats after analgesic administration and may provide a simpler alternative to existing systems. Further exploration is required to examine its sensitivity and comparative utility.