Module 07 - Environmental Enrichment

Introduction

Much of our knowledge on the effects of environmental enrichment comes from studies on rats and mice.  The most common source of information comes from our observation of the wild counterparts to our domestic and laboratory animals.  We recognize that wild animals have certain behaviours that are commonly performed.  All young animals run and jump and play and this is important for the development of strong muscles and bones, for good coordination, and for developing social skills and relationships.  They also learn discipline from adults and young animals that get out of line are likely to be punished.  Wild animals of all ages must deal with both threats and deprivations (e.g., predators, parasites, a lack of food or a poorly balanced diet, poor shelter against miserable weather, excessive cold or heat, etc.).  Laboratory animals are sheltered from these problems but are they better off?

Experimental animals were traditionally kept in caging which provided little or no social or physical stimulation.  The use of such caging was justified on the basis of reduction of disease spread, ease of sanitation, prevention of fights between animals, easy recognition of illness through measuring food and water intake, etc.  However, at the time, little consideration was given to the behavioural and psychological well-being or the stress induced by social isolation and physical deprivation. It is recognized now, that the well-being of animals is greatly improved if they are provided with opportunities for interaction with each other and their environment.  Furthermore, there is an increasing volume of literature denoting the deleterious effects of impoverished environments on experimental results. (See article by William M.S. Russell at http://www.awionline.org/www.awionline.org/pubs/cq02/Cq-intro.html)

Although the term "environmental enrichment" is used to describe efforts aimed at improving the living conditions for animals, the move is really from a very impoverished environment to a less impoverished environment.  It is unlikely that the level of complexities encountered by wild counterparts will ever be achieved within the laboratory.  Furthermore, it is possible that the well-being of an animal will not be increased by our ideas of increased complexity in its environment.   Nevertheless, the wild species are often taken as the norm against which the environment of the captive animal is measured.  Some argue that the wild and laboratory animals are no longer the same behaviourally, but most wild behaviours are seen in the laboratory animal.

The presence of a normal range of behaviours and the absence of abnormal behaviours or stereotypies is a reasonable indication that the animal is coping with its environment.  To make such judgements, we must be able to recognize normal and abnormal behaviours.  Those species that are prey animals in nature, seldom reveal that they are hurting in any way as this would be an invitation for predation.

Another approach to evaluating well-being is to use the Five Freedoms of the UK Farm Animal Welfare Council.  These freedoms were defined to give guidance to farmers on the goals of husbandry.  However, the freedoms are easily adapted to other animals and have been accepted by various groups including the World Veterinary Association and Humane Societies. 

The five freedoms are:

1. freedom from hunger and thirst (by ready access to fresh water and a diet to maintain full health and vigour)
2. freedom from discomfort (by providing an appropriate environment including shelter and a comfortable resting area)
3. freedom from pain, injury and disease (by prevention or rapid diagnosis and treatment)
4. freedom to express normal behaviour (by providing sufficient space, proper facilities and company of the animal's own kind)
5. freedom from fear and distress (by ensuring conditions and treatment which avoid mental suffering)

The freedoms are general enough to allow them to be used for any animal species and to allow for interpretation related to particular species.  They must be applied carefully with an understanding of the biology of each species and care must be taken to avoid using our own ideas as animal standards.  For example, it is customary to keep newly weaned piglets at a temperature of about 27° 0 C, day and night.  However, when the piglets had the opportunity to control the temperature themselves, they preferred a temperature of about 29°0 C during the day and about 15°0 C at night.

Terms like "discomfort" make us think about the animal's living conditions and while we tend to think of the extremes of heat and cold, or wet and dry, there are grades of discomfort in between the extremes as we know from our own experience.  A cool room is uncomfortable if we do not wear enough clothes and a hairless animal without any means of building a nest or others to huddle with may be uncomfortable at the normally recommended temperatures in the animal facility.

We can assume, given our present knowledge, that the health, nutrition and general environment needs of the common laboratory animal species are being met in present day laboratory animal facilities.  The major challenge for us is to provide them with social and physical opportunities to live and behave in a normal manner.  To do that we must have some knowledge of what a particular animal needs based on understanding their preferences.  All animals require social interactions although for some this interaction is intermittent and occurs only at breeding times.  Most wild animals occupy their days in the search for food and water.  The threat of predation is a fact of life for many small animals, including those in the laboratory where we are the predators.  To be frightened without having any means of protecting yourself is a stressful experience.  Lack of space or structure to exercise or play, in the case of young animals, is detrimental to bone and muscle development and maintenance.

The major factors to be considered then are:

• Opportunities to socialize or not
• Opportunities to occupy time during waking hours
• Opportunities to hide
• Opportunities and structure for exercise