Burn et al.(2005) compared the absorbencies of six different beddings.
The authors combared the absorbencies of 50 cubic centimeter samples of each bedding type by weighing the dry bedding samples, then soaking each one with 100 cubic centimeters of saline solution, then draining the excess liquid and weighing the wet bedding sample and subtracting the dry bedding weight to determine how much liquid had been absorbed.
The volumetric absorbencies of the beddings differed significantly. By volume, corncob was the most absorbent bedding, followed by the loose pulp beddings Omega-Dri and Alpha-Dri. Aspen woodchips, Gold Flake, and Tek-Fresh had relatively low volumetric absorbencies. Corncob absorbed about twice as much saline liquid as the least absorbent bedding, Tek-Fresh.
When comparing the beddings by mass, however, this pattern is almost completely reversed: Tek-Fresh was the most absorbent bedding by weight, while corncob was the least absorbent. Manufacturers tend to report the absorbencies of their products based on mass.
Which measurement is the most useful? Generally, when cleaning cages, the authors noted that technicians added a similar volume of bedding to each cage. The technicians either measured bedding in a metal scoop, or filled the bottom of the tray until the bedding reached the desired depth. Therefore, in practice, bedding is added to a cage on the basis of volume, not mass.
Therefore, absorbency per unit volume is the most useful measurement. Using this measurement, corncob, followed by Omega-Dri and Alpha-Dri, were the most absorbent beddings tested in this experiment.
Note that absorbency is not the only quality of bedding that affects the rats' health and welfare. Tactile characteristics, thermal properties, dust levels, and bacteria and toxin levels in them are also important characteristics of rat beddings.
Burn et al. (2006) examined the health of laboratory rats kept on aspen woodchip bedding or Alpha-Dri paper-based bedding.
The authors found no differences in the amount of ammonia generated in the cages using the two different types of bedding. All ammonia levels were quite low. However, rats kept on aspen sneezed significantly more and had significantly more lung pathology than rats kept on Alpha-Dri bedding. Forty-eight percent of rats kept on aspen bedding had moderate to severe lung pathology, compared to 26% of those kept on Alpha-Dri. Interestingly, rats keps on aspen bedding also weighed more than rats kept on Alpha-Dri. The reasons for this weight difference are unknown, but one hypothesis is that rats kept on aspen are ingesting their bedding more than rats kept on Alpha-Dri.
Based on these results, the authors recommend the paper-based bedding Alpha-Dri over aspen bedding, particularly for laboratory rats used in respiratory or dietary studies.