Mechanisms of Grazing Management in Heterogeneous Swards

Abstract

We explored the effects of heterogeneity of sward height on the functioning of grazing systems through a spatially implicit mechanistic model of grazing and sward growth. The model uses a population dynamic approach where a sward is spatially structured by height, which changes as a function of defoliation, trampling, and growth. The grazing component incorporates mechanisms of bite formation, intake, and digestion rates, but excludes sward quality effects. Sward height selection is determined by maximization of the instantaneous intake rate of forage dry mass. For any given average sward height, intake rate increased with increasing spatial heterogeneity. Spatio-temporal distribution of animal density over paddocks did not markedly affect animal performance but it modified the balance of vegetation heterogeneity within and between paddocks. Herbage allowance was a weak predictor of animal performance because the same value can result from multiples combinations of herbage mass per unit area, number of animals, animal liveweight, and paddock area, which are the proximate determinants of intake rate. Our results differ from models that assume homogeneity and provide strong evidence of how heterogeneity influences the dynamic of grazing systems. Thus, we argue that grazing management and research need to incorporate the concept of heterogeneity into the design of future grazing systems.

How do we feed grazing livestock in the future? A case for knowledge‐driven grazing systems

“…These processes influence the differentiation of small‐scale habitats and the species diversity and composition at the landscape scale (e.g., Socher et al, 2013). In turn, spatial heterogeneity of herbage species leads to less selective grazing and balances plant defoliation and restocking of nutrients (Dumont et al, 2012; Pontes‐Prates et al, 2020). Achieving these well‐balanced animal‐grazing land interactions require precise and efficient grazing management, which involves precisely timed rotations of the grazing animals and precise information about herbage availability, sward structure, and botanical composition in space and time.…”

“…These processes influence the differentiation of small-scale habitats and the species diversity and composition at the landscape scale (e.g., Socher et al, 2013). In turn, spatial heterogeneity of herbage species leads to less selective grazing and balances plant defoliation and restocking of nutrients (Dumont et al, 2012;Pontes-Prates et al, 2020).…”

Land-Use Intensification Trends in the Rio De La Plata Region of South America: Toward Specialization or Recoupling Crop and Livestock Production

“…However, heterogeneity in nutrient distribution did not affect subsequent field-scale grain yields, likely because of places with dung deposition present above-average soybean yields that compensate for eventual areas with a nutrient deficit [52] . Furthermore, for whole-system functioning and performance, sward heterogeneity may be beneficial as it may increase intake and live weight gains of grazing animals [75] .…”

Development of a Robust Sensor Calibration for a Commercially Available Rising Platemeter to Estimate Herbage Mass on Temperate Seminatural Pastures

“…Besides vegetation height, CSH might be influenced by canopy ground cover, plant structure, and plant flexibility, which are in turn influenced by seasonal variation in the botanical composition, maturity stage, and nutrient concentrations of the vegetation [18,19]. Those differences in sward characteristics are often a result of different grazing intensities and management strategies, sometimes with highly variable sward patterns in time and space [20,21]. This can further hamper successful herbage mass estimation.…”