2011 - Volume 38 - Issue 1

5-17
The Influence of Enriched Environments on Learning and Memory Abilities in Group-Housed SD Rats
by Dorte B Sørensen, Lars F Mikkelsen, Sanne G Nielsen, Annette K Ersbøll & Thomas C Krohn

Six traditional behavioural tests were done to evaluate the impact of inanimate enrichment on group housed animals. The study was performed in three parts to prevent the animals’ previous experience influencing the behavioural tests. Three traditional housing environments with increasing levels of standardized inanimate enrichment were evaluated with regard to the effect on activity, fear, learning and memory abilities in socially housed rats. The basic activity level of the animals was assessed using the open-field test. This test was combined with an amphetamine challenge test. The level of anxiety was evaluated by use of the elevated plus maze test. Secondly, a Morris water maze study was done to assess spatial learning abilities. Thirdly, two more complex learning ability tests were performed, namely the water Y-maze and the conditioned avoidance task. The different housing conditions did not influence the level of activity, the level of anxiety or the response to amphetamine. Neither did the differences in housing conditions influence the learning abilities of the animals in the Morris water maze or the Y-maze. However, in the conditioned avoidance task, rats housed in the extra-enriched environment demonstrated significantly fewer avoidances than rats housed under nonenriched conditions.

21-27
The Ability of SD-Rats to Distinguish Between Three Different Housing Environments
by Thomas C. Krohn, Lars Friis Mikkelsen, Dorte Bratbo Sørensen, Annika Maria Juul Haagensen, Axel Kornerup Hansen & Jan Lund Ottesen

Since 1986, when the Council of Europe gave the first provisions for housing of laboratory animals, the focus on housing conditions has increased with emphasis on the size of primary enclosures such as cages or pens as well as the complexity of the enclosure. Today European legislation dictates the minimum amount of enrichment to be present in cages for different species. The aim of this study was to evaluate the influence of different enrichment schemes on growth rate, water consumption, muscle strength and preference in rats, after items such as hides, nesting material, increased cage height and shelves had been introduced to the cage environment. The study demonstrated that rats spend more time in the extra-enriched cages compared to the non-enriched cages, whereas no differences in the dwelling time between the two types of enriched cages could be detected. When present in the cage, the built-in shelf was used extensively (over 40% of the observations) although no specific preference for the extra-enriched cage was detected. No differences in weight gain and water consumption could be detected between rats in the three different housing conditions, although there was a slight increase in muscle strength for the standard-enriched housed rats.

31-36
Technical Report: A Novel Porcine Model of Acute Pyelonephritis
by Louise Krag Isling, Malene Muusfeldt Birck & Páll Skúli Leifsson

A porcine model of acute Escherichia coli pyelonephritis is described. Nine female pigs with a mean weight of 19 kg were included in the study. Following laparotomy and ureterotomy, catheters were placed bilaterally in the renal pelvis. A culture of a porcine E. coli strain (109 CFU/mL, volume 3.25 mL) was inoculated unilaterally in the renal pelvis. Following bacterial inoculation, the catheter was occluded for 20 min. The inoculation procedure was repeated after two and four hrs. The contralateral kidneys served as controls and were inoculated with sterile saline. Six hrs after the first inoculation pigs were euthanized and samples of blood, abdominal swabs, urine and specimens from kidney, liver and spleen were cultured. The inflammatory response in the kidneys, renal lymph nodes, liver and spleen was evaluated both macroscopically and histologically and E. coli was identified by immunohistochemistry. E. coli was reisolated from all the inoculated kidneys and was detected immunohistochemically in all inoculated kidneys, in four renal lymph nodes from inoculated sides and in four spleens. Evidence of systemic bacterial spread was observed in five pigs. Gross and histological lesions of acute pyelonephritis comparable to human cases were demonstrated in all but one inoculated kidney. In conclusion, a novel porcine model for evaluating the pathogenesis of acute pyelonephritis was established.

39-44
The Effects of Housing on Food and Water Consumption in Da-Rats
by Krohn, TC., Farlov, H. & Hansen, AK.

According to European legislation rodents should be housed in stable harmonized groups with enrichment; a principle, which may, however, frequently be disregarded to fulfil the needs of the study. Especially in feeding studies it is necessary to house the animals individually. Literature on single housing shows an inconclusive picture, and it seems as if a range of other factors and not just single housing itself, affect the outcome of the studies on single housed rats. Therefore the aim of the present study was to evaluate the effects of single housing, enrichment and gender on the daily intake of food and water in rats. Twelve male and twelve female rats (DA/Sac) were housed either in groups or individually with or without enrichment and the daily food and water consumption was analyzed by the use of digital feeding stations. There was a significant difference between the two genders of DA rats in their eating and drinking behavior, whereas social environment only seemed to affect the eating and drinking behavior to a minor extent, while enrichment did not have an effect by itself on either of the parameters.

47-66
Effects of Alternative Housing Systems on Physical and Social Activity in Male Sprague Dawley and Spontaneously Hypertensive Rats
by Elin Spangenberg, Christina Remes, Lars Friis Mikkelsen & Katarina Cvek

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