The University of Arizona

Herbage volume per animal: a tool for rotational grazing management.

M. Duru, H. Ducrocq, L. Bossuet


The objective of this study was to provide a tool for maintaining a high grazing efficiency. In a rotational grazing system, the residual sward height does not provide enough information in advance to make the recommendation. The grazing management of 4 commercial dairy farms which differed greatly in their stocking rate, was monitored over 3 spring seasons. Data were collected on the overall grazing area (sward height measurements, stocking rate, indoor feeding, nitrogen supply) and on 3 grazed fields (herbage mass, height, and nitrogen status). At the whole grazing area level, computed data were herbage volume per animal unit (HVAU). We show that the HVAU depends on the residual herbage height. Both criteria decreased when stocking rate increased. The HVAU reflects, at the whole grazing season and area levels, how the system works on grazed field over grazing cycle. The HVAU has 2 advantages: (i) It gives rough estimation of the size of the whole grazing area to achieve a high grazing efficiency; (ii) it is a means to assess a posteriori the efficiency of the grazing system regarding the consistency between stocking rate and nitrogen supply management.



France;assessment;ewes;heat sums;dairy cows;nitrogen balance;volume determination;controlled grazing;stocking rate;rotational grazing;grazing intensity;biomass;plant height

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