Stocking density adjustment optimises grazing and limits soil ingestion of beef-on-dairy heifers

Grazing conditions that optimise herbage utilisation, together with reduced involuntary soil ingestion by livestock, may improve profitability and lower risks for animal health and food safety. Here, we assessed herbage consumption and selection and soil intake by beef-on-dairy growing cattle managed at low or high stocking densities (StockD, 5.6 and 9.2 livestock units/ha/10 days, respectively) in montane pastures. The cattle were allocated to two sub-herds (n = 32 cattle each) that grazed under a rotational grazing system. The percentage removal of grasses, legumes, and forbs was calculated for two successive 10–day grazing periods. Furthermore, n-alkanes, ytterbium, and acid-insoluble ash were used as markers for the measurements of herbage and soil intake in eight individual heifers per herd. Soil intake was higher under high versus low StockD (p < 0.001; 0.28 vs. 0.15 kg DM/day) and in period 1 compared to period 2 (p < 0.001; 0.30 vs. 0.13 kg DM/day), due to more humid weather conditions. Moreover, the percentage removal of grasses, legumes, and forbs was higher (p < 0.01) in period 1 than in period 2 but did not differ between stocking densities. The sire’s breed of heifers affected herbage intake, especially under low StockD, with a higher level in Angus than in Limousin crossbreed (p < 0.001; 7.39 vs. 5.60 kg DM/day), but not the soil intake (p = 0.61; on average, 0.22 kg DM/day). Cattle breed selection and stocking density adaptation could represent grazing management strategies for improving herbage utilisation and lowering soil intake.