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Polycarbonate and stainless steel are commonly used cage body materials for laboratory rodents. The aim of this study was to assess preference of rats for the cage material. Altogether 64 male rats were used, 32 in two different facilities. The study cages were made of either stainless steel with a polycarbonate false inner half (Kuopio) or polycarbonate with a steel false inner half (Oulu). There were four different options for alignment of false cage halves and food hopper, and likewise two options for which end of the cage faced the wall. A video camera with time lapse recording of one second each minute was used. Weekly recording started at 16.00 and ended at 01.30, and each cage was recorded when the rats were aged four, five, six. seven and eight weeks, The results were processed separately for both facilities and for day and night. Statistical analysis was done with ANOVA using alignment of food hopper to false inner cage half and direction to the wall as the main effects during the daytime the location of the rats in nontransparent steel body cages is largely governed by the light intensity created by cage walls and hopper, but stainless steel was clearly preferred in three of four possible combinations. During the night the element of tight direction became less important, but again hopper and steel combination was more attractive than the hopper and polycarbonate combination. In polyearbonate cages with false steel inner half cages: the light intensity difference had a less prominent role. However, during the day, placing the feed hopper with steel was preferred. During the night, the even distribution was indicative of a slight preference to the familiar wall material, polycarbonate. In conclusion, in both study sites stainless steel was favored in 3 out 4 possible combinations during the day, During the dark, when transparency of the material was less critical, animals accustomed to a stainless steel cages preferred steel over polycarbonate, but for animals raised in polycarbonate cages neither steel nor polycarbonate was favored., Scandinavian Journal of Laboratory Animal Sciences, Vol. 28 No. 2 (2001)

Currently, environmental enrichment studies have focused on detection of differences in group means resulting from varied enrichments. The effects of enrichment procedures on variation and hence on study results have received far less attention. Within group variation in studies is directly related to adequate sample size and thus determines ethically correct number of animals to be used. The aim of this study was to evaluate the effects of enrichment items on clinical chemistry and physiological parameters of Wistar rats with the emphasis on the extent of variation. Fortyeight weaned female and male outbred Wistar rats from eight different litters were housed for five weeks in groups of four rats per cage with an aspen tube (20x12x12 em), an aspen block (6x6x6 cm) or without enrichment items (control animals). At the end of the study, adrenals and brown adipose tissues were weighed, growth calculated from initial and final body weights and the following assays were performed from serum samples: AFOS, ALAT, ASAT, LDH, GGT, Pi, Ca, cholesterol, triglycerides, ereatinine, total bilirubin, protein and corticosterone. Based on the variation detected, SOLO Power Analysis was used to calculate the smallest number of animals required (n) to detect an arbitrarily chosen 20 % difference in all means, when significance was set at p=0.05 and statistical power at 0.90. Based on the n-values, additional N-ratio (nenrichment / ncontrol) was calculated to indicate, how many times more or less animals were needed in the enrichment group in comparison to the control group. The enrichment items did not have effects on group means. However. they seemed to influence the variation and hence on the number of animals needed, with enzyme parameters being the most sensitive in this respect. This relationship between enrichment, variation and number of animals needed should be kept in mind while designing experiments with ethically correct sample size., Scandinavian Journal of Laboratory Animal Sciences, Vol. 26 No. 3 (1999)

Female and male outbred Wistar rats (n=48) were allocated into three groups at weaning; control, tube and block groups (n = 8 males and 8 females in each) Animals were conventionally housed for five weeks in groups of four per cage with either an aspen tube (20x12x12 cm) or an aspen block (6x6x6 cm) in addition to the aspen bedding. The control animals had no enrichment items in their cages. The use of tube and block was assessed by measuring both the volume gnawed and via video recordings, which were done by the instantaneous sampling method at 1 min intervals. The growth of the animals was followed by weighing the animals three times during the study. Rats with the tubes in their cage spent over, 80 % of their time during light period inside the tube and over 20 % during dark period. Furthermore, when the lights were turned off, rats increased other contacts (on and beside) with the tube from 5 % to about 40 %. Animals with blocks spent about 3 % of their time during the light period on top of the block or in its vicinity and about 11 % during the dark period. The amount gnawed was essentially the same with both items and increased slightly with time. The enrichment items did not have any effects on the growth of the animals. In conclusion, the enrichment items have the advantage of not introducing any extra or new compounds into the cage environment, since they are made from the same raw material as the bedding. The rats used the items not only for gnawing but also for other activities. The inside of the tube was mainly used as shelter from the light The aspen tube seemed to have more enrichment value for rats than the aspen block‘ since it allowed a wider range of behaviour patterns to be expressed. These items were reusable, economical and species-appropriate for en riching the cage environment of laboratory rats. Keywords: environmental enrichment, gnawing, rat., Scandinavian Journal of Laboratory Animal Sciences, Vol. 26 No. 1 (1999)

Time mating of rodents is essential in many experimental procedures. The presence of the vaginal plug is frequently used as an indicator to confirm that mating has occurred. In rats, vaginal plugs are often deep and therefore difficult to detect by vulvar inspection. This study was carried out to assess the applicability of a human otoscope for detection of deep plugs, and the predictive value of plugs for pregnancy. A total of 132 Wistar female rats in proestrous were mated and examined for vaginal plugs on the next morning with an otoscope. All the plugs were located deep inside the vagina and could not be seen without the scope. The pregnancy rate of all females in proestrous was 69.7 %. Of all females, 72.7% had a vaginal plug and the positive predictive value of plug detection was 91.7 %. The sensitivity of the vaginal plug method was 95.7 % and specificity 80.0%. In conclusion, this study shows that detection of plugs has value for predicting pregnancies in rats. The method devised is quick, straightforward and painless to the animals and it is easily taught to technicians., Scandinavian Journal of Laboratory Animal Sciences, Vol. 25 No. 1 (1998)

How to describe bedding, that is the question. So far it has been acceptable to write down the type and manufacturer of the bedding. And maybe for quality purposes screen the bedding for pesticide and hcav y metal residues. This study focused on assessing of ten volatile organic compounds, which as a group has been combined with negative effects on animals. The commonly used European beddings were found to contain tremendously variable concentrations of these arbitrarily chosen volatile compounds. Furthermore, in most cases the concentrations went down by an order of magnitude after autoclaving. In conclusion, description of bedding in sensitive studies remains vague unless there is data on volatile organic compounds of the bedding at its final destination, the animal cage., Scandinavian Journal of Laboratory Animal Sciences, Vol. 23 No. 2 (1996)

The three commercial triple CDV vaccines used for vaccination differ by the Virus strain and the method of production. The immunogenicity of these vaccines was studied in beagle dogs under experimental conditions using neutralizing antibody titers as the measure. Differences in antibody responses were detected between the three distemper vaccines. Rockborn strain produced in canine cells (vaccine 1) induced on average the highest titers and smallest variance of serum neutra1i7ing antibodies between vaccine groups. There was also a significant difference between the 2 Onderstepoort strains (vaccine 2 and 3) inducing CDV antibodies in dogs one month after first vaccination indicating difference in antigenicity between the vaccines., Scandinavian Journal of Laboratory Animal Sciences, Vol. 23 No. 1 (1996)

Dust yield, water absorbing capacity and airborne microbes of laboratory animal beddings made of deciduous wood were compared. Three different bedding materials, aspen, alder and birch, two chip sizes and effects of a softening treatment were studied. Overall dust yield from Chips was relatively low. Aspen should, however, be preferred to alder, because it was less dusty. Small (1 X 2 X 1 mm) aspen Chips yielded less inhalable dust than the large chips (4 X 4 X 1 mm). Water absorbing capacity was better in small chips than in large chips and could also be increased with a softening procedure. In this study softening of small aspen chips resulted in unacceptable high dust yield. Though alder had a better water absorbing capacity, aspen seems to soak up urine well enough during a normal change cycle., Scandinavian Journal of Laboratory Animal Sciences, Vol. 16 No. 3 (1989)

The duration of cardiac systole and diastole in each individual cardiac cycle were measured from aortic pressure curves during vagal stimulation and mild haemorrhage with simultaneous recording of aortic baroreceptor single fibre nerve activity. The duration of cardiac diastole was highly correlated with the duration of cardiac cycle in all the interventions. The correlation coefficient between the duration of cardiac systole and the duration of cardiac cycle was not as high as that between the duration of cardiac cycle and cardiac diastole. A highly linear correlation also existed between the duration of cardiac cycle and the duration of baroreceptor inactivity time. The same was true when the duration of baroreceptor inactivity time was compared with the duration of cardiac diastole. It is concluded that the duration of baroreceptor inactivity time may inform the central nervous system about heart rate., Scandinavian Journal of Laboratory Animal Sciences, Vol. 17 No. 1 (1990)