Effect of environmental enrichment and composition of the social group on the behavior, welfare, and relative brain weight of growing rabbits

Abstract

Please cite this article in press as: Bozicovich, T.F.M., et al., Effect of environmental enrichment and composition of the social group on the behavior, welfare, and relative brain weight of growing rabbits. Appl. Anim. Behav. Sci. (2016), http://dx. a b s t r a c tThe objective of the study was to investigate if environmental enrichment and the composition of the social group would affect the behavior and relative brain weight of growing rabbits. Rabbits (72 males and 72 females) were assigned to cages with or without enrichment and one of three social groups (males, females, or mixed-gender). Two eucalyptus sticks suspended from the cage ceiling were provided in the enriched cages based on the results of a preliminary trial conducted on growing rabbits (n = 48) showing that pieces of wood (Eucalyptus sp, Pinus sp) or bamboo (Dendrocalamus giganteus) were preferred over PVC pipe (P < 0.05). Rabbits were exposed to the experimental conditions between six and 11 weeks of age. Behavioral activities were video recorded for 24 h, at 7, 10 and 11 weeks of age. Growth performance was recorded from 42 to 77 days of age, whereas skin wounds and brain weight were recorded at 77 days. At 70 days of age, rabbits in non-enriched cages showed a higher proportion of self-grooming (P = 0.012) than those in enriched cages. Enrichment decreased the number of social interactions among rabbits (P = 0.012), but increased aggressive behavior (P = 0.007). The number of animals showing skin wounds on day 77 was lower (P = 0.006) in enriched than in non-enriched cages. The incidence of social interactions was higher (P < 0.05) and of stereotypes was lower (P < 0.05) in mixed-gender groups than in same-sex groups. Female groups showed the lowest incidence of aggressive behavior (P < 0.05). The number of individuals with skin injuries was higher in mixed-gender groups (P < 0.05) than in female groups; male groups were intermediate. Growth performance was unaffected by enrichment or by the composition of social group. Males in enriched cages had heavier brains (P < 0.05) than those in nonenriched cages. Although aggressive behaviors were more frequent, the number of skin wounds on day 77 was lower in rabbits from enriched cages, suggesting improved welfare. Based on the increased frequency of social interactions and decreased incidence of stereotyped behavior, mixed-gender groups should be housed in collective cages from weaning up to 11 weeks of age. However, if the incidence of skin wounds is considered, only females can be housed in same-sex groups. For males, individual cages should be preferred. Whether environmental enrichment induces morphologic changes in male rabbits' brains should be further investigated.

‘All Ears’: A Questionnaire of 1516 Owner Perceptions of the Mental Abilities of Pet Rabbits, Subsequent Resource Provision, and the Effect on Welfare

“…Contrary to the studies outlining the welfare concerns of group housing rabbits, Bozicovich et al [ 9 ] found that group housed does within a commercial setting (that were provided with enrichment and grouped at 35 days old) demonstrated the lowest incidence of aggressive behavior. Mixed gender groups were shown to have an increased incidence of social interactions and a lower incidence of stereotypies [ 9 ]. This study advised, therefore, that mixed gender groups should be housed collectively from weaning at four weeks of age.…”

“…An appropriately enriched environment (including basic necessities for this species such as the provision of hides, items to chew on and to investigate, and open areas to run and hop) have a significant effect on welfare, as well as the behavior demonstrated between group housed individuals. For example, in a laboratory setting, provision of enrichment within a farmed rabbit setting in the form of wooden sticks to chew lead to a lower incidence of skin injuries, which could be extrapolated to pet rabbits [ 9 ]. Mullan and Main [ 4 ] suggest that the human–rabbit bond may also be strengthened with access to an enriched environment and human contact.…”

The Use of Environmental Enrichments Affects Performance and Behavior of Growing Rabbits Housed in Collective Pens

“…Among the different enrichments, gnawing materials are most commonly used. In growing rabbits kept in cages and pens with both small (2–4 animals/cage) and medium-size (13–15 animals/pen) groups, gnawing sticks have often reduced stereotyped behaviors, such as cage bar biting or chewing [10,11], aggressive interactions [12], skin wounds [13], and ear lesions [14]. On the other hand, some studies have not found a significant reduction of abnormal behaviors [15], whereas others have reported an increase of aggressive behavior when gnawing materials were provided [13].…”

Effect of A New Housing System on Skin Lesions, Performance and Soiling of Fattening Rabbits: A German Case Study

“…A possibility to enrich the rabbits’ environment is to provide them with different materials, such as gnawing sticks. These were observed to reduce aggressive behavior [11,15], injuries [10,11,39] and abnormal behaviors such as bar gnawing [40,41,42,43]. Some authors also found a positive impact of wooden sticks on daily weight gain and slaughter weight [40], and temporarily higher daily weight gain in enriched pens with a platform, hiding box and gnawing material [44].…”