Adaptive multi-paddock grazing management reduces diet quality of yearling cattle in shortgrass steppe

Authors: Jorns, Tamarah; SCASTA, J. DEREK - University Of Wyoming; Derner, Justin; Augustine, David; Porensky, Lauren; Raynor, Edward

Submitted to: The Rangeland Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2024
Publication Date: 2/6/2024
Citation: Jorns, T.R., Scasta, J., Derner, J.D., Augustine, D.J., Porensky, L.M., Raynor, E.J. 2024. Adaptive multi-paddock grazing management reduces diet quality of yearling cattle in shortgrass steppe. The Rangeland Journal. 45(4):160-172. https://doi.org/10.1071/RJ23047.
DOI: https://doi.org/10.1071/RJ23047

Interpretive Summary: Rotating cattle from one pasture to another is a management strategy often employed by producers to have cattle grazing high quality forages. Here, we evaluated the influence of adaptive multipaddock (AMP) grazing compared to traditional season-long grazing on the diet quality and composition of diets of yearling steers in shortgrass prairie. Crude protein, a measure of nitrogen in the diet, was consistently lower (13-28%) for all six years (2014-2019) when steers were grazing with AMP. These grazing season values were influenced by substantial differences early in the growing season (14-36% less crude protein in diets of steers with AMP grazing), with this magnitude of difference declining as the grazing season progressed. Knowledge about plant communities, soils, and ecological sites did alter within-grazing season contributions of different plant functional groups (e.g., cool-season perennial grass, warm-season perennial grasses, forbs) to steer diets. This adaptive management was unable to overcome much lower (11-14%) animal weight gains with AMP grazing due to the higher stocking density affecting grazing animal behavior and foraging ability. For managers employing AMP grazing in semiarid rangelands, livestock gains are expected to be less with associated reductions in diet quality.

Technical Abstract: Adaptive multi-paddock (AMP) grazing is hypothesized to improve livestock diet quality by allowing managers to move livestock more optimally between paddocks. We compared yearling steer (Bos taurus) dietary crude protein (CP), digestible organic matter (DOM), and diet composition on a ranch-scale (3,200 ha) experiment in shortgrass steppe for six years (2014-2019) in contrasting grazing treatments: Collaborative Adaptive Rangeland Management (CARM, a type of AMP with a stakeholder group making science-informed grazing management decisions) and season-long, continuous grazing (TRM, traditional rangeland management). These grazing treatments had the same system-level, within-year stocking rate but differed in stocking density, with CARM 10-fold higher. Mean grazing season dietary CP was consistently 13-28% higher in TRM than CARM; in contrast, DOM in TRM was similar to CARM or only slightly higher (2.5%). Differences in diet quality of yearling steers between CARM and TRM grazing strategies were magnified early in the grazing season with CP 14-36% higher for TRM compared to CARM steers during the first four weeks; these diet quality differences disappeared between treatments at the end of the grazing season. Combining AMP with a diverse stakeholder group’s experiential knowledge about plant communities, soils, and ecological sites did alter within-grazing season plant functional group contributions to steer diets. These efforts were unable, however, to overcome the consequences of 10-fold higher stocking density on diet quality and resulting animal performance. Managers employing AMP in semiarid rangelands should be cognizant that lower diet quality early in the growing season with high stocking density can compromise livestock gain responses.