The validity of behavioural measures of aversion: a review

Air Hunger: A Primal Sensation and a Primary Element of Dyspnea

The sensation that develops as a long breath hold continues is what this article is about. We term this sensation of an urge to breathe "air hunger." Air hunger, a primal sensation, alerts us to a failure to meet an urgent homeostatic need maintaining gas exchange. Anxiety, frustration, and fear evoked by air hunger motivate behavioral actions to address the failure. The unpleasantness and emotional consequences of air hunger make it the most debilitating component of clinical dyspnea, a symptom associated with respiratory, cardiovascular, and metabolic diseases. In most clinical populations studied, air hunger is the predominant form of dyspnea (colloquially, shortness of breath). Most experimental subjects can reliably quantify air hunger using rating scales, that is, there is a consistent relationship between stimulus and rating. Stimuli that increase air hunger include hypercapnia, hypoxia, exercise, and acidosis; tidal expansion of the lungs reduces air hunger. Thus, the defining experimental paradigm to evoke air hunger is to elevate the drive to breathe while mechanically restricting ventilation. Functional brain imaging studies have shown that air hunger activates the insular cortex (an integration center for perceptions related to homeostasis, including pain, food hunger, and thirst), as well as limbic structures involved with anxiety and fear. Although much has been learned about air hunger in the past few decades, much remains to be discovered, such as an accepted method to quantify air hunger in nonhuman animals, fundamental questions about neural mechanisms, and adequate and safe methods to mitigate air hunger in clinical situations. © 2021 American Physiological Society. Compr Physiol 11:1449-1483, 2021.

Approach-aversion in calves following injections

We assessed aversion to injections using an avoidance-learning paradigm. Holstein calves (n = 24) were randomly assigned to one of four routes of administration for 0.5 ml of saline: intramuscular (IM), intranasal (IN), subcutaneous (SC) and a null control. Calves were first trained to approach a milk reward of 1 L. Once the latency to approach the reward was consistent, calves received their assigned treatment when approaching the bottle. For the first 3 treatment sessions calves received a 1 L milk reward. This reward was then reduced to 500 mL, and then to 250 mL, and finally to 0 mL, each for 3 sessions. Compared to control calves, calves receiving the intramuscular injections showed a longer latency to approach the milk reward, but only when the milk reward was 0.25 L (P = 0.05) and 0 L (P < 0.01). Calves receiving the intranasal injections showed longer latencies relative to the controls only for the 0 L reward (P = 0.01). Calves receiving the subcutaneous injections did not differ from controls for any of the milk rewards (P > 0.2). We conclude that IM injections are aversive and that SC and IN routes are a refinement to be considered when feasible.

Stray voltage threshold is better determined under choice test conditions in sheep

Stray voltage (usually <10 V) can occur in farms. However, very little information is available related to sheep. In addition, little work has been carried out on the effects of the contextual conditions under which the animals are submitted to stray voltage. The aims of this study were (i) to determine the threshold voltage at which lambs start to express avoidance behaviour and (ii) to test if the contextual conditions (i.e. choice v. no-choice conditions) influence the determination of the threshold voltage inducing avoidance behaviour. Six-month-old female lambs fed ad libitum were trained to eat palatable pellets from one or two metallic feeders situated at the end of a 4-m long raceway. Voltage was then applied during a 2-min test to either the only feeder available (no-choice test, 1F, n = 13) or to the first of the two feeders in which the lamb started to eat (choice test, 2F, n = 13). The 1F lambs had to stop eating to avoid the voltage, whereas the 2F lambs were allowed to switch to the non-electrified feeder to carry on eating without any stray voltage. Stray voltage was applied every day, in steps of 0.5 V (AC, 50 Hz), from 0 up to 8 V. For voltages higher than 4.5 V, 2F lambs spent less time eating and ate less in the electrified feeder compared with the non-electrified feeder, and their latency to switch to the non-electrified feeder was shorter. In addition, a transient modification of behaviour was observed at 1.5 V. For 1F lambs, a decrease in the quantity of feed eaten was found for voltages higher than 5 V, although the time spent eating in the electrified feeder was not modified. Finally, 1F lambs urinated more during or just after the 2 min test than 2F lambs for voltages above 5 V. Although lambs with no choice experienced stray voltage as a negative event (increased occurrence of urination), they carried on eating in the electrified feeder whatever the voltage. Therefore, the contextual conditions in which animals are exposed to stray voltage influence their subsequent reactions: the first clear behavioural reaction threshold is easier to detect in choice than in no-choice conditions.

From an animal's point of view: Motivation, fitness, and animal welfare

To study animal welfare empirically we need an objective basis for deciding when an animal is suffering. Suffering includes a wide range ofunpleasant emotional states such as fear, boredom, pain, and hunger. Suffering has evolved as a mechanism for avoiding sources ofdanger and threats to fitness. Captive animals often suffer in situations in which they are prevented from doing something that they are highly motivated to do. The “price” an animal is prepared to pay to attain or to escape a situation is an index ofhow the animal “feels” about that situation. Withholding conditions or commodities for which an animal shows “inelastic demand” (i.e., for which it continues to work despite increasing costs) is very likely to cause suffering. In designing environments for animals in zoos, farms, and laboratories, priority should be given to features for which animals show inelastic demand. The care ofanimals can thereby be based on an objective, animal-centered assessment of their needs.