Will current rotational grazing management recommendations suit future intensive pastoral systems?

Abstract

This review aimed to determine whether current grazing management practices will suit future intensive rotationally grazed pastoral systems. A review of literature on grazing management recommendations found that there was good agreement on the ‘principles’ required for optimal grazing management. While these management practices have stood the test of time, it is concluded that shifts in external pressures (e.g., climate, plant selection and breeding, system intensification) compared to the period when farm-level grazing recommendations were first developed, may necessitate a rethink of current grazing recommendations. Examples include greater pasture masses (e.g., around 4000 kg dry matter (DM)/ha vs. the recommended range of 2600 to 3200 kg DM/ha) where short-rotation (annual, biennial) and tetraploid ryegrasses are sown, provided a consistent post-grazing residual can be maintained (possibly between 40- and 70- mm height). Milder winters and the use of ryegrass cultivars with higher growth rates in late winter/early spring may necessitate either lower target pasture covers at calving or shorter rotation lengths during winter. Longer grazing rotations (well beyond the 3-leaf stage, i.e., equivalent to deferred grazing) can be recommended for select paddocks from mid-spring into summer, to increase seasonal resilience across the farm. Longer residuals (even up to 70 mm - i.e., almost double the recommended height) might improve plant survival during periods of high stress (e.g., heatwaves, droughts). Lastly, diverse species pastures may require specific management to suit dominant species other than perennial ryegrass.

The Influence of Rotational Length, along with Pre- and Post-Grazing Measures on Nutritional Composition of Pasture during Winter and Spring on New Zealand Dairy Farms

“…Moreover, the NDF and ADF contents were also increased with longer RT. Common pasture management practice is that RT is adjusted, sometimes according to different LS or otherwise based on pasture growth rates, to maintain the optimum pasture quality and quantity [ 22 , 33 ]. The leaf regrowth stage is primarily affected by temperature, and, to a lesser extent, soil moisture [ 33 , 34 , 35 ], which can be monitored weekly or monthly.…”

“…Common pasture management practice is that RT is adjusted, sometimes according to different LS or otherwise based on pasture growth rates, to maintain the optimum pasture quality and quantity [ 22 , 33 ]. The leaf regrowth stage is primarily affected by temperature, and, to a lesser extent, soil moisture [ 33 , 34 , 35 ], which can be monitored weekly or monthly. All dairies selected in the current study were managed under the optimal LS stage (2–3 live leaves/tiller) [ 34 ] during late winter and early spring; however, LS went above the optimum (>3 leaves/tiller) during the period in late spring, where the maximum pasture growth occurred [ 36 ].…”

“…All dairies selected in the current study were managed under the optimal LS stage (2–3 live leaves/tiller) [ 34 ] during late winter and early spring; however, LS went above the optimum (>3 leaves/tiller) during the period in late spring, where the maximum pasture growth occurred [ 36 ]. When LS increases beyond the optimum, dying leaves increase fibre levels and this, along with advanced reproductive development, decrease the digestibility [ 33 , 34 ]. Therefore, harvesting a surplus of grass for conservation at peak growth is essential to maximise pasture utilisation and quality [ 36 , 37 , 38 , 39 ].…”

“…According to the DairyNZ [ 16 ] guidelines, farmers should be able to manage residual heights to between 3.5 to 4 cm, equating to 1500–1600 kg DM/ha targeted post-grazing DM. In the current study, where average residual height and post-grazing DM exceeded the DairyNZ [ 16 ] guidelines, there can be a positive effect upon pasture regrowth, and negative effects upon pasture wastage and pasture intakes at the next grazing [ 33 , 70 ]. This appears to have been the case in the present study, inasmuch as although pre-grazing DM was maintained between 2800–3200 kg DM/ha during the study period (which was within the DairyNZ [ 16 ] guidelines), the high post-grazing DM implies that pasture allocation exceeded the requirements and, therefore, the stocking rates should have been increased for more effective grazing management.…”

Effect of pre-grazing herbage mass and post-grazing sward height on herbage production and intake and performance of suckler-bred steers within a weanling-to-beef production system

“…Within technically efficient rotational grazing systems, pre-grazing herbage mass (PGHM) and post-grazing sward height (PGSH) influence pasture allocations and sward nutritive value (Frame and Laidlaw, 2011;Donaghy et al, 2021), and individually they have been shown to influence live-weight gain and stocking rate of beef cattle at pasture (Doyle et al, 2021(Doyle et al, , 2022. Compared to lactating dairy cows, grazing guidelines for beef cattle on rotational grazing temperate pasture are much less developed.…”