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13 May 2022 Evaluation of the APEX Cattle Weight Gain Component for Grazing Decision-Support in the Western Great Plains
G. Cheng, R.D. Harmel, L. Ma, J.D. Derner, D.J. Augustine, P.N.S. Bartling, Q.X. Fang, J.R. Williams, C.J. Zilverberg, R.B. Boone, Q. Yu
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Abstract

Rotational grazing studies have produced mixed results related to animal performance (weight gain), which has contributed to producer uncertainty regarding grazing management decisions. To enhance decision-support for producers, we improved algorithms in the Agricultural Policy/Environmental eXtender (APEX) model to better represent cattle weight gain in real-world rangeland conditions under two grazing management strategies. Simulated weight gain and related forage effects were evaluated with experimental data from 2014 to 2018 under two grazing strategies. The traditional rangeland management strategy used continuous season-long grazing stocked at a moderate level. The collaborative adaptive rangeland management strategy employed grazing with one large herd rotated using a sequence developed by a stakeholder group with movement between pastures driven by predetermined decision triggers. For each grazing strategy, yearling steers grazed from mid-May to October on ten 130-ha pastures. With the APEX modifications, daily weight gain was adequately simulated for both continuous (traditional rangeland management) grazing and management intensive rotational (collaborative adaptive rangeland management) grazing. Dry matter intake, total digestible nutrients, and temporal distribution of dry matter intake were the primary influencers of cattle performance (weight gain). Once shown to be accurate, we used APEX to evaluate several management alternatives (i.e., stocking rate, rotation interval, and rotation decision criteria) to showcase its decision support capabilities. These important enhancements increase the utility of APEX in semiarid environments, such as the western Great Plains, in providing science-based rangeland decision support to ranchers, agency land managers, and policy makers.

Published by Elsevier Inc. on behalf of The Society for Range Management.
G. Cheng, R.D. Harmel, L. Ma, J.D. Derner, D.J. Augustine, P.N.S. Bartling, Q.X. Fang, J.R. Williams, C.J. Zilverberg, R.B. Boone, and Q. Yu "Evaluation of the APEX Cattle Weight Gain Component for Grazing Decision-Support in the Western Great Plains," Rangeland Ecology and Management 82(1), 1-11, (13 May 2022). https://doi.org/10.1016/j.rama.2022.01.005
Received: 16 August 2021; Accepted: 25 January 2022; Published: 13 May 2022
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KEYWORDS
daily weight gain
dry matter intake
rangeland
rotational grazing
shortgrass steppe
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