Grasses

Accurate estimation of individual herbage intake in grazing ruminants is essential for improving feeding efficiency and animal performance, yet it remains challenging under field conditions. This study evaluated the association between live weight dynamics recorded by an automated walk-over-weighing (WoW) system and equation-derived herbage dry matter intake (HDMI) in dairy ewes and whether this association changed throughout lactation. The study was conducted over two years (2023–2024) using 92 Sarda dairy ewes managed under part-time grazing with two daily pasture access times (2 or 6 h day⁻¹). Live weight was recorded daily before and after pasture access, and daily live weight change was averaged weekly. HDMI was estimated using a published prediction equation based on milk yield, herbage neutral detergent fibre concentration, and pasture access time. Live weight change was partitioned into between-animal (DW_mean) and within-animal (DW_dev) components, allowing persistent differences among animals to be distinguished from short-term within-animal fluctuations, and analysed using linear mixed-effects models. In the pooled model, both components were positively associated with equation-derived HDMI (p < 0.001), while the significant DW_dev × days-in-milk interaction (p = 0.004) indicated that the association between within-animal live weight change and equation-derived HDMI decreased as lactation advanced. However, pasture access-time-specific sensitivity analyses showed that the associations with DW_mean and DW_dev persisted within AT-6h but were not detected within AT-2h, while adjustment for milk yield attenuated the within-animal association, which was no longer statistically significant, and also removed statistical support for the DW_dev × days-in-milk interaction. The mixed-effects model explained a substantial proportion of the variability in equation-derived HDMI (marginal R² = 0.64; conditional R² = 0.94), and equation-derived and model-fitted HDMI were positively correlated (r = 0.77). These findings indicate that WoW-derived live weight dynamics provide non-invasive information associated with equation-derived HDMI under the conditions of this study, but independent validation against directly measured individual herbage intake is required before their use for individual intake estimation.

The objective of this study was to evaluate the regrowth capacity of Amelichloa clandestina at different regrowth intervals after non-selective grazing in different seasons of the year. The study was carried out on a 2.23 ha⁻¹ site in northeastern Mexico. Plots of 600 m² were used, with three replications, and were subjected to grazing at 333 LU ha⁻¹ at the beginning of every season, with biweekly evaluations. Dry matter yield (DMY) was determined by harvesting 1 m² per plot and extrapolating it to kg ha⁻¹. Morphological composition was evaluated from a 10% subsample of the total biomass. The height of 12 plants and light interception were measured with a ruler and a Quantum meter, respectively. The data were analysed using a randomized complete block design (RCBD) with a split-plot in time structure, evaluating Season (S), Days After Regrowth (DAR), and their interaction (S × DAR). Means were compared using the Tukey test in JMP 14 Pro. In autumn, DMY peaked at 535.0 kg ha⁻¹ at 90 DAR (p ≤ 0.05), accompanied by a maximum canopy height of 28.7 cm and a light interception of 30.3% at the same interval. Leaf biomass was highest in autumn, with a seasonal mean of 220.8 kg ha⁻¹ across all regrowth intervals. A significant correlation was found between plant height and light interception (r = 0.67, p ≤ 0.001). Autumn favoured A. clandestina productivity under a high stocking rate.

Pasture-based livestock systems in Argentina’s Humid Pampas are increasingly confined to soils with shallow or mechanically restrictive horizons, limiting forage production even under favourable climates. Tall wheatgrass [Elymus elongatus (Host) Runemark] is one of the few forage species capable of enduring these environments. To better understand forage yield drivers, we assessed the impact of soil restrictions, water, and nitrogen availability. Shoot biomass, water and nitrogen uptake, and water and radiation use efficiency (WUE, RUE) were evaluated during autumn, spring, and summer over two years. Experimental factors included edaphic environment (differing in water-holding capacity and A-horizon thickness), water availability (rainfed vs. irrigated to potential evapotranspiration), and nitrogen (0 vs. 300 kg N ha⁻¹). Yield was challenged by the edaphic environment even under non-limiting resource supply. Water was clearly linked to yield only during summer stressful conditions, while nitrogen uptake was ever present through its impact on canopy development, thereby influencing WUE and RUE. This study demonstrates that forage yield is fundamentally constrained by the edaphic environment, with the magnitude of this response aligning with soil harshness and climatic drivers of yield.