Use of an artificial gizzard to investigate the effect of grit on the breakdown of grass

Abstract

How geese break down food in their gizzards was investigated using an artificial gizzard that was loaded with grass (blades of wheat Triticum aestivum) and different quantities of four types of grit; large and small quartzite particles and large and small glass beads. Measuring nitrogen loss from the grass indicated the extent of damage to the grass. It was found that grass breakdown in the gizzard was most effective when it contained a small quantity of quartzite particles. In contrast, glass beads in the gizzard often resulted in less damage to grass than if they were absent. This suggests that there is a trade-off between the damaging effect of grit on grass and the damaging translational movement of the gizzard lumen walls generated as the gizzard contracts. The damaging force produced by the gizzard is distributed across the gizzard contents. Thus with an increase in grit quantity in the gizzard, the force experienced by each grass particle will be reduced, resulting in reduced breakdown.