Herbage volume available per cow : a tool to manage a rotational grazing system

Abstract

Managing a grazing system requires three types of decision rules. Planning rules (average stocking rate per season) are most often developed from regional references. Operationnal rules (residual sward height) come from experiments. Usually, adaptation rules are not accurately defined, but they are driving variables for adding or removing grazed plots. For the efficient management of a rotational grazing system, these three types of decision rules should be consistent in order to optimize the grazing efficiency. By grazing monitoring in three sets of farm enterprise, we show that the herbage volume available per animal unit (HVA  sum of the of the products: plot area*sward height) is an indicator making it possible to link up the different types of decision rules. Morever, detailed observations on sward structure for different amounts of HVA enable us to define threshold of HVA which could be used to reconcile plot recommendations and simplicity of grazing management.