Document Type

Thesis - Open Access

Award Date

2025

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Jameson Brennan

Second Advisor

Hector Menendez

Abstract

Heifer development on dormant rangelands offers a cost-effective alternative to feedlot or drylot systems. However, traditional bunk supplementation methods often result in uneven intake, inefficient feed use, and ecological degradation around static feeding sites. This thesis evaluated the integration of precision livestock technologies and a dynamic Range Supplementation Model to improve individual animal performance, weight uniformity, and rangeland sustainability in extensive heifer development systems in the Northern Great Plains. The first study involved a seven-month trial (November 2023–May 2024) with 50 yearling Angus heifers grazing dormant native rangelands at the SDSU Cottonwood Field Station. Heifers were stratified into two treatments: a control group fed a fixed daily ration (3.1 kg/hd) via conventional bunk feeding, and a precision group fed individualized supplement amounts using an electronic identification enabled SmartFeed Pro™ feeder. Supplementation for the precision group was dynamically adjusted every two weeks using the Range Supplementation Model, which utilized real-time body weight data from SmartScale™ units and accounted for projected performance and forage quality. While average daily gain (ADG) did not significantly differ between groups (Precision: 0.91 ± 0.04 kg/hd/d, Control: 1.0 ± 0.04 kg/hd/d, P = 0.1302), both groups exceeded the breeding target weight of 381 kg, and final body weights were affected by supplementation strategy (Precision: 398.49 ± 3.10 kg/hd, Control: 420.03 ± 5.17 kg/hd; P = 0.0079). Precision-fed heifers consumed 2,303 kg less supplement, resulting in $56.56 per head in feed savings, and achieved more uniform final weights (coefficient of variation, CV = 5%) compared to the control group (CV = 8%). Although outcomes showed intake variability that may have impacted the model’s accuracy, findings demonstrate that integrating PLTs with targeted modeling can reduce overfeeding, enhance uniformity, and maintain performance benchmarks while lowering total feed input. The second study examined the ecological impacts of precision supplementation by assessing how short-term rotations of the mobile SmartFeed Pro™ feeder influenced plant communities and soil health. Unlike traditional bunk sites, which are associated with overgrazing, compaction, and invasive species encroachment, biweekly precision feeder rotations were designed to reduce prolonged animal congregation in any one area. Results indicated that precision animals spent significantly more time at supplementation locations than bunk fed animals (Precision: 164.5 minutes/day, Control: 89.5 minutes/day; P < 0.001), resulting in a significant decrease of invasive forbs (Feeder: 23.2% ± 5.92, Pasture: 43.2% ± 5.92; P = 0.0244), while maintaining stable native perennial grass (Feeder: 78.5% ± 7.32, Pasture: 79.3% ± 7.32; P = 0.932) and forb cover (Feeder: 10.0% ± 1.76, Pasture: 7.6% ± 1.76; P = 0.343). Biomass was also significantly lower in precision fed locations (Feeder: 1,116 ± 135 kg/ha, Pasture: 1,630 ± 135 kg/ha; P < 0.01), leading to an increase in bare ground (Feeder: 10.3% ± 1.99, Pasture: 3.1% ± 1.99; P = 0.0176) and greater soil compaction, with an average of 70 mm greater soil depth in the surrounding pasture (P = 0.0009). With continued refinement, these technologies offer a scalable solution for improving the efficiency and sustainability of heifer development programs in extensive grazing environments.

Library of Congress Subject Headings

Heifers -- Development.
Heifers -- Feeding and feeds.
Beef cattle.
Plant communities.
Precision farming.
Rangelands.
Range ecology.

Publisher

South Dakota State University

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Rights Statement

In Copyright