Gut loading is the process by which an animal's prey is raised and fed nutritious foods with the intention of passing those nutrients to the animal when the prey is eaten. For example, crickets bred for frog food are often dusted with calcium or other nutrients, including fat and protein, so as to supplement the frog's diet.
Several commercial products are available and are fortified specifically for gut loading. These products often include varying combinations of fat, protein, vitamins, and fiber.
Among the hypotheses conceived by scholars about the possible manufacturing processes employed by 16th and 17th centuries string makers to produce all-gut bass strings, that of loading the gut by means of appropriate treatments deserves serious consideration, on the ground of direct and indirect confirmations at our disposal.
A general characteristic consequent to the loading of gut is that of requiring no particular twisting techniques since the high specific weight increase, by noticeably reducing the working diameter produces a remarkable decrease in the string's stiffness.
To confute the hypothesis of gutloading, the only alternative is to maintain that the basses of the lute -whose bridge-hole diameters were recorded- worked at a tension between 1 and 2 kg.