True mineral digestibility in C57Bl/6J mice

Abstract

Data on mineral digestibility is key to understand mineral homeostasis and refine the recommendations for the dietary intake of these nutrients. In farm animals and pets, there is plenty of data on mineral digestibility and influencing factors. In laboratory mice, however, there is a lack of information on mineral digestibility under maintenance conditions, although this should be the basis for studies on mineral homeostasis under experimental conditions. The aim of the present study was to analyse data on intake, faecal excretion, and apparent digestibility of calcium, phosphorus, sodium, potassium, and magnesium in C57BL/6J mice fed different maintenance diets with varying voluntary dry matter intake. Lucas-tests were used to quantify true digestibility and describe correlations between dietary intake and excretion/absorption of the nutrients. Calcium, phosphorus, and magnesium showed a linear correlation between intake and faecal excretion (R2: 0.77, 0.93 and 0.91, respectively). Intake and apparently digested amounts of sodium and potassium were correlated linearly (R2: 0.86 and 0.98, respectively). These data show that intake is the major determinant of absorption in the minerals listed above. Faecal calcium and phosphorus excretion were correlated as well (R2 = 0.75).

Digestibility of crude nutrients and minerals in C57Bl/6J and CD1 mice fed a pelleted lab rodent diet

“…The apparent phosphorus digestibility of both mouse lines in this study was slightly higher than that found previously in C57Bl/6 J strain 20 . Phosphorus intake and apparently digested amount of phosphorus were correlated linearly (R 2 = 0.88) and the mean true phosphorus digestibility amounted to 81%.…”

“…This difference might be due to the different natural type of diet (herbi-omnivorous vs. herbivorous), but can only be speculated upon in this study. The Lucas-test for calcium in the mice showed sufficient linearity (R 2 = 0.73) and the resulting mean true digestibility of 65% is much higher than the value of 33% found in C57Bl/6 J mice in four diet groups in a previous study 20 . The feed intake per mouse per day was considerably lower in the present study, which may have a positive influence on calcium absorption via faecal DM excretion.…”

“…The C57Bl/6 J mice hat a significantly higher apparent magnesium digestibility than the CD1 mice ( p < 0.001) and C57Bl/6 J mice in literature 20 . The Lucas-test showed a strong linear correlation between magnesium intake and the apparently digested amount over data from both genetic lines, resulting in a nearly complete true digestibility (97%).…”

“…In the present study, the mice were group-housed to pool faecal samples per cage. This is a reliable method for digestibility trials in mice 11 , 20 for several reasons: Mice as social animals prefer to live in groups. By pooling the faeces per cage, the time of sampling can be kept short to minimize the stress for the mic and it also reduces the inter-individual variation which adds reliability to the results.…”

“…In meta-analyses on different species 17 – 19 and the authors´ own previous trials in mice 20 , quantitative estimations of gastrointestinal mineral absorption could be calculated from data on intake and digested amount. By regression analysis in the form of Lucas-tests 21 , it is possible to test for uniformity of absorption and estimate the true nutrient digestibility.…”