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Summary Laboratory Animal Science
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LABORATORY ANIMAL SCIENCE1- Different forms of barrier systems
Barrier systems are preventive hygiene measures. It is applicable to different levels: for a complete or
partial facility, one or several rooms, a group of cages and one single cage. The purposes are
protection of the animal, protection of the personnel and protection of the environment, the higher
the risk, the tighter the barrier is.
Barrier unit
A barrier unit has five essential characteristics:
1. complete germ-tight unit from which the clean zone can be disinfected
2. a lock for the transfer of material or animals
3. ventilation, sterile air in and out
4. lock for the staff
5. the possibility to control the clean zones from the outside
Isolator
It already exist for a long time, it is a complex construction and very expensive to buy and maintain.
Later on there was the introduction of the flexible film isolator or Trexler isolator. It has its pro’s and
con’s like cheap, simple to handle and the use of peracetic acid as disinfectant as a con there is the
risk of perforation. The isolator also has five essential characteristics:
1. a closed sterile room from which the content and the inside can be sterilized
2. possibility to observe the content from the outside
3. lock to pass materials and animals through
4. ventilation system, sterile air supply and exhaust of dirty air
5. possibility to work and handle the animals from the outside
Differences with the barrier unit are gloves instead of a personnel lock and you have no direct
contact with the animals.
Ventilated cabinets
Those cabinets are sealed airtight and can be used under neg and pos pressure. There is a controlled
environment and light cycle. The animals must be handled in laminar flow.
Filter cages
The first filter cage was in glass wool, later on in polyester. The pro’s are:
- effective hygiene barrier, so you can use it for the housing of immune deficient animals
- prevention of cross-contamination, you can house animals of different origin, hygiene – health
status and isolation of different experimental groups within the same room
- with these cages you are limiting the animal-related aerosols and allergens
- protection against sudden changes in the environment
- low cost
The con’s are:
- handling of the animals must be done in a laminar flow
- there is a micro-environment you need to maintain
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,Individually ventilated cages
These cages have extra benefits:
- superior micro-environment (the air is changed a lot)
- less cage changes are necessary (less bedding and less autoclaving)
- in this way you protect the staff and the environment
- this can be placed in older animal houses
2- How do you get inbred strains and what is it?
Inbred means the breeding of closely related individuals resulting in an increase in homozygosity of
the pups. The degree of inbreeding is expressed as inbred coefficient F = fraction of original
heterozygous genes that become homozygous. The more generations of inbreeding, the more F
increases. The increase of F per generation is determined by the relation between the parents
(degree of consanguinity).
They speak of inbred after at least 20 successive generations of brother * sister breeding or mating of
offspring * youngest parent. Then F will be 98.4% so this means that 98.4% of the originally
heterozygous loci have become fixed in a homozygous state. There is still some variation but they are
quite genetically uniform = isogenic strain.
But in inbred strains growth, fertility and vitality can decrease. If you mate between related parents
there is a high chance that the descendant becomes homozygous for a recessive allele. So by
inbreeding the individual is fixed into an arbitrary combination of genes, but not necessarily the most
beneficial, we call this an inbred depression. The animals function worse compared to the original
population, so the effects of unfavourable alleles are more pronounced in homozygous condition. In
the first 4-8 generations there are a lot of drop outs because of the unfavourable gene combinations,
you need more than 10 generations so the most unfavourable alleles dropped out, so a new
balanced system develops.
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, 3- Stress in animals, how can you recognize it?
recognize via physiological parameters.
There is acute and chronic stress, the definitions are:
Acute: state of an organism that appears with a sudden decrease in predictability and/or possibility
to influence relevant changes in environment.
Adrenocorticotropic hormone is released.
There is an increase in the production of corticosterone and cortisol.
Epinephrine and norepinephrine are released; BP and HR increase, constrict certain blood vessels,
more glucose is made in the liver, the animal is prepared to fight or flight.
Stress is an adaptive mechanism, the changes in the body system allow the animal to adapt and
survive dangerous situations.
Cannot adapt in a state of chronical stress.
Chronic: state of an organism that appears when relevant changes in environment cannot be
predicted or influenced during a long period of time.
Stomach acid levels increase and the hippocampus shrinks (altering the capacity to remember).
How to deal with stress? Adaptability
Environmental enrichment = increase the controllability and consequently decrease stress.
Active and passive coping strategy. Which strategy the animal chooses, depends on the genotype and
experience of the individual.
Measuring the well-being
Based on biological parameters:
- productivity decreases
- physical health
- physiological criteria (BP, HR)
Based on behaviour:
- test of preference = let the animal choose a cage for example
- abnormal behaviour (ambivalent and redirected = toward animals, humans, other + completely
different behaviour)
- stereotype behaviour
- cognitive functioning; difficulties to learn or to solve problems when they are in a situation they are
not comfortable in
- latency time eating; animal that is not at ease will take long before it starts to eat
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