Effects of Alternative Housing Systems on Physical and Social Activity in Male Sprague Dawley and Spontaneously Hypertensive Rats
Two alternative rat cages and their effect on home cage physical and social activity were evaluated in maleÂ Sprague Dawley (SPD) and Spontaneously Hypertensive (SH) rats for 10 weeks. Rats were housed strainwiseÂ in pairs in ST cages, in groups of eight in Enriched Rat Cage System (ERC) equipped with a shelter andÂ wall-hung ladders, and in groups of eight in four interconnected Scantainer NOVO cages (NOVO), equippedÂ with shelves. Home cage activity was assessed through direct observations and effects were studied inÂ exercise tests, parameters related to physical activity and in the Elevated Plus Maze (EPM). Effects ofÂ within-group variation on the minimum sample size needed to detect a treatment effect were calculatedÂ for the different cage types. The home cage activity was highest in NOVO cages, followed by the ERCÂ cages. This was supported by the higher locomotor and exploratory activity in the EPM and an improvedÂ performance in the last exercise test, compared to ST-caged rats. Aggressive and submissive interactionsÂ were higher in NOVO cages compared to ST cages. The design of the NOVO cages, if connected, mightÂ induce both a higher activity level and more aggression. The hypertension and insulin resistance typicalÂ of the hypertensive rat model were not influenced by an increased home cage activity. No major effectsÂ of alternative cage types were found on within-group variation. The activity was not enough to create aÂ distinct training effect but prevented exercise-related parameters from deteriorating during the study and isÂ therefore still relevant for the health and welfare of the animals. Additional benefits of the alternative cagesÂ are qualitative, since they stimulate a wider range of behaviours, social interactions and offer possibilitiesÂ for the rats to control their situation.Â
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