Physiology and behavior

Monitoring the physical appearance

Animals in poor health experience reduced welfare and animal experiments may be influenced by infections or diseases. Therefore international guidelines set standards for the regular health monitoring of laboratory animals (KRAFT et al. 1994). Although such standards mostly focus on infections, they also demand monitoring for pathological changes, which can be regarded as welfare indicators. Apart from this, obvious signs of diminished well-being are injuries that may occur due to stress as described above (chapter 2.6.2.1).

Monitoring serum parameters

The secretion of adrenal medullary and cortical hormones leads to an increased blood glucose level, but it can also be reduced by strong activity. Blood glucose is known to rise during stressful situations in rats, e.g. electric shock (NATELSON et al.

1977), exposure to ether (GÄRTNER et al. 1980) and transfer into a new cage (DE BOER et al. 1989). Therefore it gives information about the state the animal is in. For example, in rats exposed to a new room, a new cage or the sound of an alarm bell a 10 - 15% rise in plasma glucose was found (ARMARIO et al. 1986). However, after immobilization or low ambient temperature the plasma glucose levels of mice initially increased, but then decreased below the baseline (QUIRCE & MAICKEL 1981).

of handling, blood sampling, intraperitoneal saline injection, and cage movement (KRULICH et al. 1974; SEGGIE & BROWN 1975; GÄRTNER et al. 1980). SEGGIE &

BROWN (1975) as well as GÄRTNER et al. (1980) show that within one minute of stimulation a rise of the prolactin level occurs with a peak concentration 8-15 minutes later.

The use of catecholamines as indicators for well-being is difficult because these transmitters are released within 1-2 seconds after perceiving the initiating stimulus (BROOM & JOHNSON 1993). Furthermore, the catecholamine levels of catheterized rats increased when opening the cage door, and an even larger increase occurred during handling the rats and transferring them into a new cage (KVETNANSKY et al.

1978).

ACTH can serve as in indicator of well-being and the function of the adrenal cortex, respectively. Prolonged exposure to stress may lead to a sensitized SAM axis and using an ATCH challenge test, functioning as a novel disturbing stimulus, elicits a greater response (BROOM & JOHNSON 1993). When a stressful stimulus affects the animal the plasma level of ACTH increases very fast. For BALB/cByJ mice ANISMAN et al. (1998) could prove that after a straining event ACTH increases rapidly within the first minute, but in the course of the following two minutes it decreases almost to the basal value. When measuring ACTH it has to be taken into account that there is an effect of the age on the ACTH secretion. A study by SAPOLSKY et al. (1983) found out that old rats elicit an adrenocortical response to acute stress, but they were less able to terminate this response via glucocorticoids-mediated feedback inhibition of ACTH release.

Corticosterone: see chapter 2.6.2.2

Body weight monitoring

Straining situations lasting a longer period of time lead to a decreased body weight (SCHÜLER & BORODIN 1978; MCGRADY & CHAKRABORTY 1983; ALARIO et al.

1987; RESTREPO & ARMARIO 1989) whereas situations associated with well-being, for example routine handling of rats (SVENDSEN & HAU 1994), can increase the body weight.

Cardiovascular monitoring

The heart rate describes the beats of the heart per minute. If an animal has performed muscle work or if it gets excited the heartbeats per minute will increase.

These changes of the body function during emotional taxing situations are evaluated in the neocortical structures of the brain, which then activates the sympathetic nervous system and deactivates the parasympathetic nervous system (SHAPIRO et al. 1993). Both nervous systems influence the heart function: with the sympathetic nervous system increasing the heart frequency and the parasympathetic nervous system decreasing it. Most of the time as a result the plasma catecholamines concentrations increases which leads to an increased heart rate and NIEZGODA et al. (1993) postulates that there is only a short latency between the taxing situation and the body response. But it has always to be considered that the heart rate can increase before an action occurs, and that an emotional response to a situation may also be a bradycardia (BROOM & JOHNSON 1993), which occurs in animals that show freezing responses (STEENBERGEN et al. 1989) and those that are air-breathing animals well adapted for diving. Additionally, although the heart rate is characterized by a high sensitivity, there is only a low specificity (WALL 1992).

Furthermore, HAROUTUNIAN & CAMPBELL (1981) could prove that a rapid repetition of acoustic and visual stimuli leads to a habituation regarding the heart rate. In general the measuring of the heart rate is an appropriate parameter in order to evaluate short-term strain in animals (GEERS et al. 1994; BROOM 1995) provided that the biology of the animal and its social status is kept in mind (BROOM &

JOHNSON 1993).

Monitoring the body temperature

The core body temperature is influenced by the circadian rhythm but it can increase as a response to disturbing events. In laboratory rats the body temperature increased by a mean of 1.4°C during a storm and during the visit of unfamiliar humans in the animal room (GEORGIEV 1978). A study by VON HOLST (1986) with tree shrews reveals that the body temperature of an animal defeated by another one decreases.

As mentioned above it is necessary to understand the animal’s biology when trying to assess welfare by using the body temperature.

Monitoring behavior

The behavior of animals can give unique insight into their feelings of pleasure and aversion (ROLLS 1999). Therefore it is indispensable to measure their welfare (FRASER & DUNCAN 1998). As laboratory animals have been domesticated for many generations it sometimes is difficult to compare captive animal behavior with that performed by their wild relatives. Nevertheless, there are some constant characteristics of poor and good welfare. On the one hand play behavior and exploratory behavior are reliable indicators for good well-being. These two behavioral patterns are assigned to the group of ‘luxury’ behavior, which principally functions to gather information about the physical and social environment. Luxury behavior is typically only performed when there is no pain and suffering and the basic survival needs are met (DUNCAN 1998). On the other hand according to SAMBRAUS (1982) an animal showing signs of abnormal behavior is not healthy. The term ‘abnormal behavior’ describes any behavior that differs from species-specific behavior regarding modality, frequency or intensity and bearing the possibility to evoke harm (MEYER 1984). If the artificial environment is extremely different from the species’

natural habitat it may occur that an adaptation is not possible (WECHSLER 1993). A

frequently observed abnormal behavior is called ‘stereotypy’. It means that captive animals show behavioral pattern that are permanently repeated and are connected with specific structures in the environment. This behavior develops from behavioral pattern of the normal behavior repertoire and seems to be of no use. Stereotypies indicate that the housing conditions do not meet the animal’s requirements (KÖNIG &

WAIBLINGER 2001). Nevertheless, the occurrence of stereotypic behavior is closely related to the secretion of endorphins in the CNS and therefore stereotypies can be regarded as a ritualization of conflicting behavior having a significant biological function for the animal. It is generally accepted that animals performing stereotypic behavior experience chronic stress and for this reason housing conditions provoking stereotypies should be avoided (VAN ZUTPHEN et al. 1995)