Braconnier, M., Gómez, Y., Gebhardt-Henrich, S. G. 2020. Different regrouping schedules in semi group-housed rabbit does: Effects on agonistic behaviour, stress and lesions. Applied Animal Behaviour Science 228, 105024.

Although group housing of naturally social animals like rabbits (Oryctolagus cuniculus) is desirable for ethical reasons, social conflicts can significantly increase the risk for injuries as well as stress incidences and negatively affect their welfare. A common housing system in Switzerland is the "semi group-housing". Here, rabbit does are kept individually shortly before the birth of their kits until 12 days post-partum (pp) after which they are regrouped. Despite positive aspects of this housing system, like the reduction of pseudo pregnancy and crushing of kits, fights between the does often occur after the regrouping process. This study examined whether prolonged postpartum separation may reduce agonistic interactions, stress, and lesions. In total, data were collected over 5 trials on 57 Hycole breeding does. Per trial, three groups of 8 does each were artificially inseminated on day 10 pp and regrouped on either day 12, 18 or 22 pp. Non-pregnant does were replaced in every trial. Agonistic behaviour, anogenital distance, lesions and increased body temperature, as a stress indicator, were documented. The effect of the regrouping treatment on the rate of injury and agonistic interactions was different depending on the trial (lesions: interaction trial x treatment χ2 = 44.21, df = 8, P < 0.0001; agonistic interactions: interaction treatment x trial χ2 = 23.59, df = 8, P = 0.003). During winter trials (November- February), the numbers of lesions and agonistic interactions were generally lower than in the trials during summer. None of the animals with temperature transponders showed a body temperature increase after regrouping (P = 0.98), however, there was an increase after the artificial insemination (P = 0.019). The anogenital distance, measured during the artificial insemination process, was not correlated to the aggressive behaviour of does (r = 0.028; P = 0.78). These findings suggest that prolonging single housing only reduced lesions and fighting in some trials but failed to do so in others. Group composition, individuality and season are discussed as relevant factors for the extent of agonistic interactions. Against our expectations, in none of the groups a stress response after regrouping was found according to body temperature measures.

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