Animal and pasture responses in contrasting temperate pasture-based cattle management systems: set-stocking versus cell grazing

Abstract

Grasslands cover a significant portion of the Earth's land and offer many benefits. In the UK, they constitute the largest agricultural area and support livestock production. Traditional set-stocking (SS) and continuous grazing methods allow animals to selectively graze more palatable and nutritious plant parts and species, boosting individual animal productivity in the short term but can be detrimental to long-term pasture productivity. Cell grazing (CG), an intensive rotational system, is proposed as an alternative that can enhance system productivity and profitability through increased pasture production, utilisation, and stocking rates; with potential to optimise natural resource use (e.g., land) and mitigate environmental impacts (e.g., soil carbon sequestration). A 4-year study at Rothamsted Research's North Wyke site in southwest England compared animal and pasture responses under SS and CG stocking methods using a split-block design with three replicates (enclosures) per treatment. The SS enclosures (1.5-1.75 ha) were continuously grazed with fixed stocking rates, and CG enclosures (1.0 ha) were rotationally grazed with flexible daily grazing area allocations and stocking rates. Grazing occurred from spring to autumn, using two cohorts of autumn-born dairy × beef steers, each grazed for 2 years before slaughter. Measurements included standing herbage mass (weekly), herbage chemical composition (fortnightly), steer liveweight (monthly), and botanical composition (spring 2018 and 2022). DM intake was estimated based on animal energy requirements. Significant interaction effects (P < 0.05) were found for most variables, apart from metabolisable energy, ADF and NDF which were affected by treatment (P < 0.05) and year (P < 0.001), and DM content which was affected by year only (P < 0.001). Average daily gain was higher in SS (0.77 kg/d) than CG (0.60 kg/d), linked to higher estimated DM intake (7.2 vs 6.2 kg DM). However, annual liveweight (LW) production per hectare was greater in CG (687 vs 476 kg LW/ha, respectively), due to higher total pasture production (6 053 vs 3 667 kg DM/ha, respectively) and stocking rate (2 362 vs 1 290 kg LW/ha, respectively). Herbage nutritional quality varied, with CG having higher metabolisable energy and water-soluble carbohydrates, and lower fibre (ADF and NDF) concentrations. Changes in botanical composition also varied between treatments. The proportion of perennial ryegrass increased under CG (42-69%, P < 0.001) but declined under SS (36-16%, P < 0.01). These results highlight that while SS can enhance individual animal gains, CG improves total system productivity and pasture composition. Long-term, replicated experiments like this are crucial for evaluating the long-term viability and sustainability of differing stocking methods and grazing management strategies.

Keywords: Continuous stocking; Dairy × beef cattle; Grazed pasture production; Perennial ryegrass sward; Rotational stocking.