Longer rest periods for intensive rotational grazing limit diet quality of sheep without enhancing environmental benefits

Abstract

Intensive rotational grazing systems (also called cell grazing, holistic grazing or time-controlled grazing) are often implemented to improve production and environmental outcomes. Over recent years there has been considerable interpretation and adaption of the holistic principles that guide the management of these systems. In southern Australia, this has led to an increasing use of longer rest periods for intensive rotational grazing. This experiment was established to compare three intensive rotational grazing strategies (fast rotation [FR], average 57-day rest; slow rotation [SR], average 114-day rest; and flexible grazing [FX], based on availability of green herbage mass) with continuous grazing (CG) to assess the impact these systems have on vegetation and diet quality. The grazing treatments were run across three production zones (PZs) in the landscape (low [LPZ], medium [MPZ] and high [HPZ]) to determine whether management by landscape interactions influenced vegetation. Pasture composition was mostly influenced by PZ in the landscape with Microlaena stipoides and Holcus lanatus more prevalent in the HPZ and Rytidosperma spp. more common in the LPZ. The intensive rotational grazing treatments all had greater herbage mass and ground cover than CG. Composition change often occurred in one PZ and not another (e.g. Hypochaeris radicata increased with SR in the LPZ), or there were contrasting effects in different parts of the landscape (e.g. M. stipoides increased with FR compared with CG in the HPZ but decreased in the LPZ). Diet quality was lower for the SR compared with the other grazing treatments. Maintaining a post-grazing benchmark of >0.5 t green DM ha⁻¹ was associated with a higher diet quality. Based on this two-and-a-half-year study run during poor seasons, it can be concluded that intensive rotational grazing can be managed, with fast and flexible rotations, to achieve per head animal performance similar to CG, but with higher herbage mass, ground cover and a desirable pasture composition.

Keywords: ground cover, holistic grazing, landscape variability, native pasture, pasture composition change