Breed differences and temporal dynamics of sheep diet selection relevant to sequential sheep-cattle grazing in northern mixed-grass prairie

Authors: KERSH, AARON - University Of Wyoming; SCASTA, J - University Of Wyoming; Derner, Justin; LIMA, P M T - University Of Wyoming; STEWART, WHIT - University Of Wyoming

Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2026
Publication Date: 3/26/2026
Citation: Kersh, A.J., Scasta, J.D., Derner, J.D., Lima, P., Stewart, W.C. 2026. Breed differences and temporal dynamics of sheep diet selection relevant to sequential sheep-cattle grazing in northern mixed-grass prairie. Small Ruminant Research. 259. Article e107768. https://doi.org/10.1016/j.smallrumres.2026.107768.
DOI: https://doi.org/10.1016/j.smallrumres.2026.107768

Interpretive Summary: Ranchers wanting to employ targeted livestock grazing in semiarid rangelands with many plant species have a myriad of tools in their management tool box regarding the when to graze (timing), how long to graze (duration), and does livestock breed influence selection of the plants targeted for control. We evaluated three breeds of sheep (Dorper, Rambouilet, and Hampshire) for their grazing behavior when target grazing native northern mixed grass prairie with a targeted plant for control (plains larkspur, a toxic plant to cattle). Dorper ewes had a greater preference for forbs compared to Rambouilet and Hampshire - which did not differ. Targeted grazing duration showcased that about 1 week of grazing was sufficient to demonstrate declines in forbs (like plains larkspur) before the sheep changed to greater selection of native forage grasses. This suggests that ranchers can employ short durations of targeted grazing with sheep that can highly reduce forbs (including toxic plants like plains larkspur) without negatively impacting perennial forage grasses for cattle.

Technical Abstract: Optimizing targeted grazing in multispecies systems - particularly those containing diverse forb and toxic plant species - requires understanding how grazing timing, duration, and livestock breed affect diet selection. In this study, we assessed how sheep breed, age, and grazing period influenced forage use across a 51-day grazing trial in a northern mixed-grass prairie. Dorper, Rambouillet, and Hampshire ewes (n = 15 each) and 139 Dorper lambs sequentially grazed 3-ha paddocks (n = 4) for 9-14 days based on forage availability. Paddocks supported a diverse plant community (~ 23 forage species), including plains larkspur (Delphinium geyeri Greene). Body weights were recorded within each paddock to assess performance alongside dietary shifts. Diet composition - focusing on larkspur, graminoids, and other forbs - was estimated via fecal DNA metabarcoding and focal bite counts collected relative to time in paddocks. Dorper ewes exhibited a strong preference for forbs (19.2% ± 2.3), significantly higher than Rambouillets (7.7% ± 1.4), Hampshires (7.9% ± 1.2), and Dorper lambs (11.4% ± 1.6; p = 0.03), with correspondingly lower graminoid intake. Focal bite counts revealed inflection points around 7-9 days where forb selection declined (17.4% to 1.7%) and graminoid intake increased (80.7% to 98.3%), offering rotation cues to preserve forage for cattle. Although larkspur intake was low (0.5-1.5%), it varied with timing (p = 0.001) but not by breed or age (p > 0.4). These findings support the use of strategic breed- and timing-based grazing designs to suppress undesirable forbs while conserving graminoids in multispecies systems.