Patch-burn management changes grazing behavior of cattle in humid subtropical grasslands

Authors: BOUGHTON, RAOUL - Archbold Biological Station; SMITH, BRITT - Us Geological Survey (USGS); BOUGHTON, ELIZABETH - Archbold Biological Station; GOMEZ-CASANOVAS, NURIA - Texas A&M University; Bernacchi, Carl; DELUCIA, EVAN - University Of Illinois; SPARKS, JED - Cornell University; SWAIN, HILARY - Archbold Biological Station

Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2024
Publication Date: 7/1/2024
Citation: Boughton, R.K., Smith, B.W., Boughton, E.H., Gomez-Casanovas, N., Bernacchi, C.J., DeLucia, E., Sparks, J., Swain, H.M. 2024. Patch-burn management changes grazing behavior of cattle in humid subtropical grasslands. Agriculture Ecosystems and the Environment. 368. Article 109012. https://doi.org/10.1016/j.agee.2024.109012.
DOI: https://doi.org/10.1016/j.agee.2024.109012

Interpretive Summary: Subtropical grasslands, such as those found throughout Florida, are commonly used for cow-calf grazing for the intended purpose of producing calves to transport to ranches in other parts of the country. How, when, and where cattle graze is important for both the quality of the cattle and the impacts on the grassland ecosystem. As with all grasslands in subtropical areas, burning is a very important component of management to ensure high quality regrowth and to prevent undesirable plants from taking hold. While traditional management practices utilize entire pasture grassland burning, a new management practice, known as patch burning, shows promise to improve ecosystem functioning while allowing for higher quality grass for cattle to graze upon. Patch burning relies on burning one-third of each pasture each year and results in all areas being burned after three years. This differs from traditional burning in which the entire pasture is burned once every three years. We tested whether cattle prefer the recently burned areas of patch burn by tracking cattle movement using GPS collars on a subset of cows. The recently burned patches showed much more cattle grazing than the non-burned patches. The cattle were much more likely to move uniformly around the burned patch in the patch burned fields whereas in the fully burned fields the cattle grazed much less evenly. These results suggest that patch burning pastures can lead to preferential grazing patterns among cattle and further research is being pursued to understand how these grazing patterns impact the grasslands themselves.

Technical Abstract: Humid, subtropical grazing lands utilized for cattle production are significant agroecosystems that are important for economic production, global food security, and biodiversity. Prescribed fire, an important management tool, is used for controlling woody plant encroachment, maintaining wildlife habitat, and stimulating forage regrowth. Fire also interacts with grazing to maintain grassland structure and heterogeneity. Understanding this fire-grazing interaction is important to producers because spatio-temporal cattle behavior has been linked to both livestock production and environmental impact through patterns of pasture utilization. The goal of the study was to understand how two fire regimes affected spatial and temporal grazing behavior, including grazing intensity, grazing evenness, and circadian and seasonal grazing patterns. A randomized block design experiment was established in 2017 with 16 pastures (16'ha each), at Archbold Biological Station’s Buck Island Ranch in FL, USA. We examined two prescribed fire management techniques, one represented the prevailing practice of the region with prescribed fire applied to entire pastures (full burn = FB), and the other ‘alternative’ regime applied patch-burn (PB), in which one-third of a pasture was burned each year. Here we present results from the first year of the study, after the first patch-burns and the full burns were implemented. Global Positioning System data loggers on cows recorded 5-min location fixes to track cows and cattle grazing behavior was inferred based on distances between GPS locations. Cattle behavior was significantly different in PB vs. FB pastures. Over a year with five grazing periods, cattle spent on average 38% more time grazing in burned vs unburned patches within PB pastures. PB burned patches were also grazed with a more even spatial distribution compared to unburned patches. In contrast, in FB pastures, cattle grazing intensity and evenness were similar across the entire pasture. Time of day, temperature, season, and fire treatment all had small effects on the circadian cattle grazing patterns. Our study suggests that PB can be a management tool to manipulate cattle behavior in humid subtropical grazinglands, with potential implications for pasture utilization and beef production, carbon and nutrient cycling, and wildlife habitat.