In the former paragraphs some of the most widespread measures of physical quality
from a manufacturers point of view are evaluated. However, other criteria exist to
evaluate feed physical properties. These criteria are for instance water absorption index
(WAI), water solubility index (WSI), and sinking velocity (SV), all criteria being useful
in e.g. fish feeding. Other criteria well related to properties of the raw materials from
which feeds are manufactured are the angle of repose, bulk density and specific weight.
These criteria can be used to characterise the different feeds or feedstuffs. Some of these
criteria can be related to complete feeds as well. For a more fundamental description of
both methods and theories on physical properties related to characterising plant and
animal materials, the reader is referred to Mohsenin (1986). Since these criteria are not
specific for pellets as such, and thus not within the scope of this study, they are not
discussed.