FUNCTIONAL-MORPHOLOGY OF THE GIZZARD OF THE DOMESTIC GOOSE - DESIGN OF AN ARTIFICIAL GIZZARD

An artificial gizzard was developed to investigate the functional basi s of the asymmetry of the gizzard muscles of herbivorous birds, such a s the domestic goose (Anser anser). Two types of gizzard muscle morpho logy were modelled: asymmetric muscles that generated a translational movement; and symmetric muscles that generated a compressional movemen t. The extent of breakdown of grass in the artificial gizzard was esti mated by measuring nitrogen loss from blades of wheat (Triticum aestiv um). The effect of grit and its interaction with the two types of gizz ard muscle movement were also explored. In the artificial gizzard, tra nslational movements caused more damage to grass than compressional mo vements and the damaging effect of grit was greatest when there was a translational movement. This type of movement was found to be particul arly important as it prepares plant material for subsequent processing by stripping the matrix cells from the fibre bundles. Without such pr eparation, the breakdown of grass is limited.