Herbage volume per animal: A tool for rotational grazing management

Abstract

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.

Improvement of Time‐Driven Models of Lamina Cocksfoot Digestibility by a Process‐Based Model to Take Account of Plant N Nutrition and Defoliation

“…For the laminae, differences between seasons were interpreted as being due to lamina age, which was precisely assessed. Nevertheless, the average number of green or partially green laminae per tiller (Table 3) is an indirect way of assessing the average leaf age, assuming that the greater the number of laminae, the higher is the average age (Duru et al. 2000).…”

“…2001). The latter effect is due to a shorter leaf growth duration associated with N fertilizer application (Duru et al. 2000).…”

“…We propose to do it through residual sheath length instead of the residual sward mass as it is easier to record residual sheath length routinely. Furthermore, it is the sheath length that drives the development stage of leaves on tillers (Duru et al. 2000).…”

“…For seedlings, the rate of plant development can be quantified through the leaf insertion level (Groot et al, 2003) that is linked to the lamina length (Wilson, 1976). For established swards, we have suggested that the sheath length drives the lamina length (Duru et al. 2000) and in this way can easily explain the effects of cutting date and especially the grazing intensity on plant development.…”

“…It allows distinguishing two processes to be distinguished for explaining herbage digestibility changes (Lemaire & Allirand, 1993): (i) one depends on plant growth through the ontogenic decrease in the metabolic: structural tissue ratio; (ii) the other is linked to the differentiation of structural tissues. The structural tissue component increases in relation to the appearance of new leaves (Wilson, 1976), which become progressively longer as the plant grows (Duru et al. 2000).…”