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Session: Beef Species and Ruminant Nutrition Symposium I: Historical and Current Estimates of Bovine Composition and Energetics - Sponsored by Cactus Feeders, Inc.

90 - Evaluating the Difference Between Formulated Dietary Net Energy Values and Net Energy Values Determined from Growth Performance and Estimates of Shrunk Body Weight Gain in Finishing Beef Cattle

Monday, June 27, 2022

10:20 AM – 11:00 AM CT

Location: Oklahoma City Convention Center, Ballroom B

Presenting Author(s)

KH

Kristin E. Hales

Thornton Distinguished Chair
Texas Tech University
Lubbock, TX

Author(s)

MG

Michael Galyean

Paul Whitfield Horn Professor
Texas Tech University
Lubbock, TX
Zachary K. Smith, n/a

Assistant Professor
South Dakota State University
Brookings, SD

Abstract: The California Net Energy System (CNES) was developed more than 50 yr ago and partitions energy into NE_m and NE_g, both of which can be calculated for feedstuffs as a cubic function of dietary ME. Recovered energy (i.e., NE_g) can be calculated from NE_m requirements, dry matter intake (DMI), and shrunk body weight gain (SWG). Thus, if body composition can be reliably estimated relative to maturity, SWG and DMI can be used to calculate performance-adjusted net energy values using a quadratic solution. Likewise, SWG can be predicted from 13.91 × RE^0.9116x EQSBW^-0.6837. Evaluating observed vs. predicted values of NE_m, NE_g, and SWG enables nutritionists to better understand differences in maintenance energy requirements, efficiency of energy use, associative or antagonistic effects of feedstuffs, nutrient deficiencies, and environmental factors. Our objective was to use feedlot performance and carcass data from numerous pens of cattle fed at two locations to identify potential weaknesses in the CNES equations by evaluating factors affecting residuals between calculated dietary NE_m and NE_g values based on NASEM (2016) tabular values and performance-based NE_m and NE_gvalues. With adjustments to address beef industry changes, the CNES will continue to maintain functionality in practical beef production.