Patch Mow Grazing: Investigating the Effects of Mowing on Forage Nutritive Value, the Biomass–Nutritive Value Relationship, and Herbivore Selection

Authors

Trace R. Stauble, University of Nebraska-LincolnFollow

First Advisor

Nicholas McMillan

Committee Members

Dan Uden, Mitch Stephenson

Date of this Version

11-2025

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Agronomy

Under the supervision of Professor Nicholas A. McMillan

Lincoln, Nebraska, December 2025

Comments

Copyright 2025, Trace R. Stauble. Used by permission

Abstract

Herbivore foraging behavior plays a critical role in shaping grassland structural heterogeneity, with selection often driven by forage biomass and nutritive value. Currently, it is thought that herbivores primarily select areas that are greater in nutritive value, and low in biomass. More specifically, disturbances like fire and grazing have been thoroughly studied showing that recently burned and grazed areas are not only higher in nutritive value but disproportionately selected by herbivores in comparison to undisturbed areas. However, most studies address only narrow ranges of defoliation, comparing intensely defoliated sites (< 10 cm) to those that are either not defoliated or have experienced a much longer time since defoliation, thereby decreasing grazing pressure as biomass increases. However, one of the most widely used methods of defoliation in grasslands, mowing, hasn’t been thoroughly studied for its effects on nutritive value, and how it impacts herbivore selection. Our study aimed to (1) evaluate how mowing treatments—i.e., short (5 cm), medium (18 cm), and tall (>30 cm, unmown)—affect nutritive value and herbivore selection, (2) assess the relationship between biomass and nutritive value in a patch mown landscape (3) assess how forage biomass and nutritive metrics, including crude protein (CP) and total digestible nutrients (TDN), influence selection. We found that nutritive value was significantly greater in short-mown patches (5 cm) compared to other patch heights (18 cm to 30+ cm), while biomass was inversely related to nutritive value and digestibility regardless of treatment. Furthermore, we found that cattle selected for our short-mown patches 15–30% more than medium and tall patches. Selection was significantly greater in low biomass areas in comparison to high biomass areas. Areas with higher CP were selected for more than areas with lower CP, and areas with higher TDN were selected for more than those with lower TDN. Our study shows that mowing to a short height significantly increased nutritive value, and also herbivore selection. Our results suggest that herbivores prefer to graze in lower biomass higher nutritive value areas, demonstrating that the mechanism currently driving the creation of heterogeneity is achievable through other methods of defoliation, with defoliation intensity, resulting in lower biomass and higher nutritive value areas, likely being the driver of herbivore selection.

Advisor: Nichols A. McMillan