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Housing conditions for laboratory animals can affect animal well-being and experimental results. There are guidelines for laboratory animal husbandry but these are insufficiently based on objective research and thus may not reflect the actual needs of the animals. In order to evaluate housing conditions for laboratory mice, we developed a non-invasive preference test system. The possible application of the multiple-choice housing system is as follows. Individual mice can be offered different housing conditions in different test cages. During the test period the movements of the mice between the test cages can be detected automatically. Simultaneously, behaviour of the animals can be recorded with a mouse-directed video system. When interpreted with caution, combined analyses of relative dwelling times and animal behaviour can give information on the preference of mice for the housing conditions under study. The results can advance the selection of proper housing conditions for laboratory animals. In this paper, a detailed description of our preference test system is given and its validity discussed.

Background: The reason for the high prevalence of mild cobalamin (vitamin B-12) deficiency in the elderly is poorly understood. Objective: We aimed to determine the reason for this high prevalence. Design: We examined cobalamin intake, the presence and severity of atrophic gastritis, the presence of Helicobacter pylori infection, and plasma cobalamin and methylmalonic acid (MMA) concentrations in 105 healthy, free-living, older subjects aged 74‐80 y. Results: Mild cobalamin deficiency, ie, low to low-normal plasma cobalamin concentrations ( 0.32 mmol/L), were found in 23.8% of subjects; 25.7% of subjects were not cobalamin deficient (plasma cobalamin ♢ 260 pmol/L and plasma MMA ≤ 0.32 mmol/L). Six subjects (5.8%), including 1 with mild cobalamin deficiency, had dietary cobalamin intakes below the Dutch recommended dietary intake of 2.5 mg/d. Mildly cobalamin-deficient subjects had lower total (diet plus supplements) cobalamin intakes (median: 4.9 mg/d; 25th and 75th percentiles: 3.9, 6.4) than did non-cobalamin-deficient subjects (median: 6.3 mg/d; 25th and 75th percentiles: 5.4, 7.9) ( P = 0.0336), mainly because of less frequent use of cobalamin supplements (8% compared with 29.6%; x 2 = 3.9, P = 0.048). Atrophic gastritis was found in 32.4% of the total study group: mild to moderate in 19.6% and severe in 12.7%. The prevalence of severe atrophic gastritis, but not mild-to-moderate atrophic gastritis, was higher in mildly cobalamin-deficient subjects (25%) than in non-cobalamin-deficient subjects (3.7%) (x 2 = 4.6, P = 0.032). The prevalence of immunoglobulin G antibodies to H. pylori was similar in mildly cobalamin-deficient subjects (54.2%) and in non-cobalamin-deficient subjects (44.4%) (x 2 = 0.5, P = 0.5). Conclusions: The high prevalence of mild cobalamin deficiency in healthy, free-living, older Dutch subjects could be explained by inadequate cobalamin intake or severe atrophic gastritis in only 28% of the study population. Other mechanisms explaining mild cobalamin deficiency in older people must be sought. Am J Clin Nutr 1998;68:328‐34.

The type of bedding material has been reported to affect the environment in both the animal cage and animal room. It has an impact on the health and well-being of the animals and may cause biased experimental results. Requirements for bedding materials, particularly those regarding animal comfort are poorly supported by experimental data. In this study, various types of bedding material were evaluated using preference tests with mice and rats. It was found that beddings consisting of relatively small particles (-1.2 × 1.6 mm2) were generally avoided, whereas beddings consisting of large fibrous particles were preferred. The characteristics of the bedding materials were further investigated by scanning the size and shape of the particles, and by the assessment of ultrasound produced by the moving of the beddings. The results seem to indicate that size and manipulability are among the main determinants of the appreciation of bedding particles by laboratory mice and rats, and larger particles are preferred.