Assessing animal priorities: future directions

Pekin ducks are motivated to access their nest site and exhibit a stress-induced hyperthermia when unable to do so

The origins of floor-laying in ducks could be low motivation for a nest, or stress related to difficulties with accessing a nest (e.g. competition). Using a behavioural demand test, we investigated if increasing the work required to access their nest impacted ducks' behaviour and two indicators of stress: egg corticosterone concentration and elevation of core body temperature (stress-induced hyperthermia (SIH)). Twelve laying Pekin ducks previously trained in an operant push-door task were required to use a push-door to access their nest. The door was loaded with increasing weight (0-160% of individual BW, four nights per workload) and eventually blocked to prevent nest access. Before testing, temperature data loggers were implanted in the abdomen. Eggs were collected daily to measure corticosterone concentrations. Behaviour towards the push-door was quantified. Three birds were excluded from the experiment at an early stage. Five of the nine remaining birds pushed all workloads up to 160% BW and attempted to pass the blocked door, with another two birds pushing up to 80 and 140% BW. For those that pushed at all workloads (n = 5) the area under the curve (AUC) of hyperthermia was larger at workloads of 80% (P < 0.001), 120% (P < 0.01), 140% (P < 0.001), 160% (P < 0.001), and when the door was blocked (P < 0.001), compared with 0%. On the first night when the door was blocked, all five birds pushed more at the door, but no attempts were made to push on the following 3 nights, yet the AUC of hyperthermia did not differ between nights 2-4 of the blocked door, compared with the first night that the door was blocked. Increasing workload and inability to access the nest had no effect on corticosterone in egg albumen. It was concluded that laying Pekin ducks were motivated to access a nest. Although it was not possible to differentiate metabolic from psychogenic stress on the first night that nest access was denied, we suggest that the occurrence of hyperthermia on the subsequent nights was due to SIH resulting from frustration at their inability to use their preferred nest. Floor-laying therefore is unlikely due solely to low nest-seeking motivation. Egg corticosterone was not a relevant indicator of acute stress. Strategies to improve nest availability (e.g. decreasing competition) could improve the welfare of commercial ducks.

The use of demand functions to assess behavioural priorities in farm animals

The use of demand functions to identify the behaviours most important to animals has been advocated widely. The principle is to place increasing cost on the opportunity to perform several behaviours and subsequently to rank these behaviours according to the change in their performance as a function of cost; this change is described by the elasticity of the demand function. However, the method has been criticised for placing the animal in too artificial a setting. Firstly, the animal works repeatedly for short periods of access to a resource, which may interrupt bouts of behaviour; secondly, animals are tested in isolation, which may affect their motivation to perform the target behaviour; and, finally, assumptions regarding the effect of prior deprivation and reward duration on elasticity of demand need to be tested. This criticism, however, is important only if these factors do affect the elasticity of the resulting demand function. This paper reviews experiments that have developed methods to assess the importance of various behaviours to farm animals and that have tested the effect of social context, length of deprivation of a resource and reward duration. It is concluded that the elasticity of demand function may be used to assess the relative importance of various behaviours, but that it is important to make sure that the experimental set-up yields valid estimates of the elasticity of demand.

Behavioral evaluation of the psychological welfare and environmental requirements of agricultural research animals: theory, measurement, ethics, and practical implications

The welfare of agricultural research animals relies not only on measures of good health but also on the presence of positive emotional states and the absence of aversive or unpleasant subjective states such as fear, frustration, or association with pain. Although subjective states are not inherently observable, their interaction with motivational states can be measured through assessment of motivated behavior, which indicates the priority animals place on obtaining or avoiding specific environmental stimuli and thus allows conclusions regarding the impact of housing, husbandry, and experimental procedures on animal welfare. Preference tests and consumer demand models demonstrate that animal choices are particularly valuable when integrated with other behavioral and physiological measurements. Although descriptive assessments of apparently abnormal behavior such as stereotypies and "vacuum behaviors" provide indications of potentially impoverished environments, they should be used with some caution in drawing welfare conclusions. The development of stereotypies may in some cases be linked to psychiatric dysfunction and reflect underlying neurophysiological impairments, which have implications for the ability to perform flexible behavior and thus the quality of research data provided by this kind of behavioral measurement (e.g., in pharmaceutical research). Environmental modifications, commonly termed "enrichment," can have diverse consequences for cognitive function, physiological responses, health, psychological welfare, and research data. Simple practical modifications of housing, husbandry, and experimental design are suggested to improve the psychological welfare of agricultural research animals in accordance with the principles of refining, reducing, and replacing (the "3Rs"), which underlie US Public Health Service Policy, and prevailing public ethics.

A concept of welfare based on reward evaluating mechanisms in the brain: anticipatory behaviour as an indicator for the state of reward systems

In this review we attempt to link the efficiency by which animals behave (economy of animal behaviour) to a neuronal substrate and subjective states to arrive at a definition of animal welfare which broadens the scope of its study. Welfare is defined as the balance between positive (reward, satisfaction) and negative (stress) experiences or affective states. The state of this balance may range from positive (good welfare) to negative (poor welfare). These affective states are momentary or transient states which occur against the background of and are integrated with the state of this balancing system. As will be argued the efficiency in behaviour requires that, for instance, satisfaction is like a moving target: reward provides the necessary feedback to guide behaviour; it is a not steady-state which can be maintained for long. This balancing system is reflected in the brain by the concerted action of opioid and mesolimbic dopaminergic systems. The state of this system reflects the coping capacity of the animal and is determined by previous events. In other words, this integrative approach of behavioural biology and neurobiology aims at understanding how the coping capacity of animals may be affected and measured. We argue that this balancing system underlies the economy of behaviour. Furthermore we argue that among other techniques anticipation in Pavlovian conditioning is an easy and useful tool to assess the state of this balancing system: for estimating the state of an animal in terms of welfare we focus on the conditions when an animal is facing a challenge.

How The Hierarchical Organization of the Brain and Increasing Cognitive Abilities May Result in Consciousness

Defining perception, awareness, consciousness and reflexive or self-reflexive consciousness is difficult. I will not linger on definitions of fuzzy concepts but will attempt to put forward evidence for the rationale that awareness is likely to emerge as a consequence of how the brain processes information. Efficiency in information processing has resulted in a limited number of preferential (motivational) states of the brain and, in fact, of the whole organism. In addition, animals have the ability to internally represent external conditions and, through interactions with the motivational state, generate expectations.

It is argued that optimal decision-making requires that possible sequences of behaviours each activate their associated neuronal networks representing cue- and context-related information. Prior to the initiation of an action, the consequences of each possible scenario are estimated. An efficient animal must have the ability to anticipate, weight and choose. This weighting occurs at a hierarchically higher level and results in signals which possess a coordinative function in activating the appropriate motivational state, response selection, activation of associated networks and maintenance of attention.

Higher cognitive executive centres perceive and recognize such signals and integrate ongoing behaviour with internal representations about the past and expectations within the context of the signal induced state. Humans experience these simultaneously-occurring processes as awareness. The nature of the subjective experience may vary from an emotional state to reflexive consciousness depending on the cognitive abilities of the species and the stage of development and the level of arousal in the individual.