Use of Gnawing Hay Blocks: Effects on Productive Performance, Behavior and Reactivity of Growing Rabbits Kept in Parks with Different Sex-Group Compositions

SIMPLE SUMMARY: Alternative cage-free housing systems for growing rabbits, such as parks/elevated pens, are currently being developed in Mediterranean countries. In these parks, the inability to express gnawing behavior and fear are the top behavioral-welfare-associated consequences. Gnawing inability promotes abnormal stereotypical and aggressive behaviors. Fear can be reduced by avoiding aggression. Thus, the present study aims to evaluate the effect of gnawing compressed hay blocks and sex-group composition (only females, only males, mixed sex) on the productive results, behavior, and reactivity of growing rabbits in a park system. None of the animals showed injuries due to aggression at the end of the trial. The provision of gnawing blocks affected rabbit behavior negligibly but improved their reactivity towards a new environment or a new object; thus, the inclusion of gnawing blocks should be recommended for animal welfare. Changes in sex-group composition were not relevant in terms of either quantity or quality of performance and conspecific interactions. ABSTRACT: To improve animal welfare in collective park housing systems, this study assessed the effects of the provision of gnawing hay blocks and the group composition (F: females, M: males, FM: mixed sex) on performance, behavior, and reactivity of 288 growing rabbits reared in 18 parks (16 rabbits/park) from 31 to 73 days of age. The presence of gnawing blocks inside the feeding area of the parks scarcely affected performance and budget time, but decreased the time spent in the resting area compared to parks without blocks (p < 0.001); it increased the time spent moving during the open field test (p < 0.05) and the rate of rabbits that approached the object in the novel-object test (p < 0.05). As for sex-group composition, the feed conversion ratio was lower in parks F and FM than in park M (p < 0.05). During the open-field test, FM rabbits spent more time moving (p < 0.05), whereas M rabbits displayed self-grooming for a longer time (p < 0.01). Results related to production, behavior, and reactivity indicate the provision of gnawing blocks for welfare improvement, but do not support the change from current mixed-sex to single-sex rearing.