Module 05 - Research Issues

Animal Care and Handling Factors

Animal Stress 

Transportation Stress 

Laboratory animals are rarely used in the same location where they are raised, so usually they are transported to the facility where the research will be done. A number of studies have shown that animals experience varying degrees of stress as a result of the transport, and that it takes some time upon arrival at the research facility to return to a normal physiological state. Eating, drinking and growth tend to return to normal levels in about a week after delivery to the new location. Some subtle physiological and immunological changes may last longer. A common recommendation is to allow laboratory animals at least one week conditioning after transport to the research facility.

Housing Factors

Caging

The amount of space per animal, and the number of animals per cage may influence an animal's response in an experiment. Identical caging should be used for all animals in a study, to ensure that the space per animal and number of animals per cage remains consistent within a study.

Studies have shown that the number of rodents per cage affects the stress level (either isolation or crowding), and their growth. As a general rule small rodents should be housed in small groups to minimise stress, and for social enrichment. If the research requires individual housing, this should be scientifically justified to the animal care committee.

Environmental Enrichment 

The value of providing an enriched environment in improving the well-being of the animals, must be emphasised. In the context of controlling research variables however, it must be noted that any changes (improvements) to the cages will have behavioural, physiological and anatomical effects, some of which result in permanent changes to the animal. (Module 10 provides a more in-depth discussion on environmental enrichment.) Therefore any improvements or enrichments should be uniformly and consistently provided to all animals for the duration of an experiment. Changes in the cage's physical environment should only be made following consultation with the investigator.

Routine (Daily/Weekly) Animal Care and Husbandry

The daily routines of the animal care staff may have a profound impact on the way an animal responds in an experiment. As a general principle all animals should be handled the same way, and the same time of day. Handling must be gentle, and consistent. Most animals quickly become familiar with their regular caretakers, and their stress level rises when unfamiliar people handle them.

The kind of handling each animal receives may in fact alter its behaviour or physiology, and thereby affect its response in a study. One example of this comes from a handling study conducted in pigs. Hemsworth and co-workers published a paper in 1986 describing a study in which the responses of pigs to three kinds of handling; pleasant handling, unpleasant handling and minimal handling, were compared. The pigs exposed to pleasant handling approached people more quickly (not surprising). The females receiving pleasant handling were different with respect to age at first estrus and sexual receptivity when bred, and had a significantly higher pregnancy rate than the other two groups. Although not a statistically significant results, the males receiving pleasant handling reportedly had larger testicles. 

While it is interesting to speculate whether these results can be correlated with human teenage behaviour, they do emphasise the point that how the animals are handled affects their behaviour, physiology, and anatomy. Consistent handling, by animal care staff, by research technicians, and by the investigators, will ensure that this source of variability is minimised.

The weekly routine in any animal room must also be understood by the investigator. In many facilities, animal cages are cleaned once or twice weekly on specific days. Taking samples just after the cages have been cleaned may result in altered results because of the disturbance of the animals at that time. In addition, it must be noted that weekend and holiday animal care routines are generally different than regular week day routines. This may alter the animals' responses on weekend days if sampling is scheduled then.