Efeito da presença de um coespecifico no alojamento de ovelhas em novo ambiente, após estresse agudo causado pelo transporte

Abstract

Background: Sheep are social and gregarious animals. They feel at ease when free and clustered rather than isolated. In some situations, as in experimental procedures, they need to be separated from the flock and kept without social company. Both instances, separation from the flock and isolation are considered stressful and may impact their well being. As stress can affect the results of the study, special care should be taken when conducting biomedical or veterinary research. The aim of this study was to compare the concentration of cortisol and behavior of ewes housed at a research institution in the presence of a familiar conspecific, an unfamiliar conspecific or in the absence of conspecifics. Materials, Methods & Results: Experimental procedures were approved by the Research Ethics Committee of Hospital de Clínicas de Porto Alegre, RS, Brazil. Eighteen Corriedale ewes were divided into three groups. Group I (n = 6): the experimental sheep was housed with a familiar conspecific, an adult Texel sheep, kept in the same experimental flock of sheep throughout the study. Group II (n = 6): the experimental sheep was housed with a conspecific stranger, also an adult Texel sheep, but from a different flock. Group III (n = 6): the experimental ewe was kept in social isolation, without contact with conspecifics. Each ewe was transported from the source property to the location of the experiment, always at the same time, where remained under observation for six hours. A total of five blood samples for cortisol was collected: a baseline (before transportation), upon arrival at the experiment site and two, four and six hours after arrival. Animal behavior was recorded during the six-hour stay at the experimental site with a miniature camera. We assessed time of interaction with conspecifics, time spent on having food and water, rest, the number of bleating and number of steps. There were not statistically significant differences in measurements of cortisol between groups using repeated measures ANOVA. Statistical difference (P <0.05) was observed on arrival (time 0 h), after transport in all groups, with a mean increase in plasma cortisol concentration of 259% (minimum=26% and maximum=1032%, standard deviation=261%). This study assessed the time two hours from the peak concentration of cortisol (time 0 h), by percentage, to minimize the differences among animals. Group I showed a decline of 54.08% (standard deviation 18.53); Group II, 43.52% (standard deviation 8.81); and Group III, 30.19% (standard deviation 14.30). Group I was statistically different from Group III (P <0.05). Behavioral analysis showed no statistical difference in the parameters. Discussion: The presence of a conspecific was found to be important in reducing the stress in the early hours in the new environment, observed by a decline in cortisol concentration. The decline was greater when the conspecific was known. Due to variability between animals, behavioral differences between groups were not shown. The separation of sheep and transport caused a significant increase in levels of cortisol, which corroborates literature describing these two procedures as stressors. Thus, we highlight the importance of achieving acclimatization for animals undergoing transport and accommodation in a new environment.