Abstract
Comparative studies on the housing of single and pair-caged female laboratory rabbits
In this study the housing of laboratory rabbits in an unstructured metal cage commonly used in laboratories (laboratory cage) has been compared with the housing in a structured larger cage (environmental cage). Each cage type was tested for its suitability for housing single and paired female nonreproductive laboratory rabbits. A total of 48 chinchilla bastard laboratory rabbits were examined in four groups of 12 animals at 3.5 months, 5.5 months and 7.5 months of age. In general, the entire behavioral repertoire was checked for low activity around midday and high activity in the evening. These ethological analyses were supplemented by examining the animals´ health, weight, weakness of hocks and changes in hopping.
Results:
Laboratory cage
The single cage (43x54 cm = 2.322 cm2) had so little space that the animals could only attempt to hop. Doubling the cage floor area enabled the animals to hop only with short steps.
Even though rearing was attempted by rabbits up to adulthood, this characteristic exploratory behavior could not be carried out with a cage height of 36.5 cm.
Due to the lack of space, hopping ability of almost all 7.5-month-old rabbits sank from "good" to "sufficient" in 50% and to "insufficient" in the other half of the group.
The stainless steel cage harms the animals´ hocks. There were two cases of broken claws, and all hocks showed thick epidermis or calluses at age of 7.5 months.
Single-caged rabbits in the laboratory cage had the largest mean weight gain caused by frequent eating and little exercise due to boredom. Stereotypical behavior such as biting bars was seen less often in single-caged rabbits than in the environmental cage, but they bit water bottles and pushed them out of their mountings more frequently.
SUMMARY 143
Pair-caged rabbits in the laboratory cage had social contact with their counterparts 9.4-18.7% of the total time, predominantly expressed as lying in contact with the other rabbit. Sexual and aggressive behavior was rare. Harmful biting resulted in three injuries. Relaxed lying of both animals was rarer than in the other systems and was due to the lack of space.
Environmental cage
With a cage floor area of 4.658 cm2 (3.220 cm2 open area, 1.438 cm2 area under the shelf), the animals were able to hop with short steps. They often hopped around the stable leg of the shelf.
A cage height of 66 cm allowed the animals to completely rear for exploration.
The period of locomotion was two to three times higher than in the laboratory cage.
Jumping up and down from the shelf may slow down morphological changes in hopping motion, but it was not prevented. The ability to hop deteriorated in most of the animals by the age of 7.5 months from "good" to "sufficient", and to "insufficient" in only one animal.
The shelf as an environmental enrichment was used by single-caged animals 5.4-30.4 % and by pair-caged animals 9.3-30.5 % of the observation time.
In the environmental cage single-caged rabbits used the enriched system equipped with resting shelf and hiding place in the same way as the pair-caged animals. These animals showed bar biting most frequently.
Compared to the other groups the pair-caged rabbits in the environmental cage moved more than all other rabbit groups. They ate less than the other groups and had the lowest mean weight gain. Social behavior comprised 18.2-26.6% of the observation time, pointing to a lively interest in the other animal. This was predominantly expressed by lying in contact with the other animal. In spite of the possibility of retreating to the shelf or hiding under it, the rabbits cared for their social counterpart much more often in the environmental cage than in the laboratory cage. There was one clash in which one animal was bitten in the ear.
144 SUMMARY
Assessment of the two cage types:
Laboratory cage
According to welfare requirements, the laboratory cage for single-caged animals is not appropriate for the housing of rabbits due to the lack of space. Even increasing the floor area by using the "double cage" is not adequate, since the low height of the cage, which prevents rearing, and little stimulation remain unchanged.
When rabbits were kept as a pair in the laboratory cage, the subordinate animal cannot retreat or escape when a dominant animal is chasing it. The nonstructured cage is not appropriate for the animals despite the lower number of injurious fights.
Environmental cage
In the environmental cage, rabbits ý with the exception of adult males - should only be kept as singles when used for testing special scientific hypotheses. Because of frequent bar biting, the cage should be enriched with attractive objects for gnawing.
For housing female rabbits in pairs, the environmental cage shows more space than prescribed by the minimum regulatory requirements. In addition, it offers places to retreat, which is very favorable for animals to socialize and exercise. The solid shelf is used for sitting, lying, jumping or hiding. The rabbits seem to "communicate" in this cage type.
Conclusions:
The housing standards for caging rabbits fixed in the EC guidelines are inadequate to house rabbits in accordance with animal welfare requirements.
In contrast, the environmental cage tested in this study offers a larger living space, an adequate height and structure (e.g. hiding place combined with resting shelf) suited to rabbitsý needs. We recommend installing these cages in laboratories and housing rabbits in pairs, if possible.
A larger living space of adequate height structured with different functional areas as in the environmental cage is particularly suited to rabbits´ needs. Installing these cages in laboratories may establish pair caging for different scientific objectives.
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