Sward prehensibility in cattle and sheep

Abstract

Sward prehensibility expresses the facility with which the grazing animal prehends the sward. It is a major determinant of herbage intake, and on an heterogeneous sward, it may partly influence diet choices.

Sward prehensibility may be assessed through the characteristics of the prehending bite of the grazing animal (dimensions, mass, time required) its expression will therefore be modulated by the interactions between the characteristics of the sward and those of the grazing animal.

This paper reviews the different methodologies used in the study of sward prehensibility, the current state of knowledge on the mechanisms involved by cattle and sheep during bite prehension and on the different components of sward prehensibility, together with the predictive criterion that may be proposed.

Sward prehensibility is determined by the ease with which the sward is gathered into the mouth (which depends on height of the vegetation, on sward bulk density, on stiffness of the herbage, and on the necessity of a selection between more or less palatable food items), by the ease with which the herbage is broken, by the presence of ’barrier’ components (pseudostems, stems and dead material) and by its dry matter content. Green leaf mass per ha constitutes the most precise predictive criterion of sward prehensibility, although it does not take into account all factors involved.