Influence of Vegetative Diversity During the Stocker Phase on Carcass Characteristics and Economic Returns of Beef Steers

The following research summary is sourced from the South Dakota State University Animal Science Research Report 2024. This study examined how long-term grazing intensity and resulting vegetative diversity influence carcass traits and economic returns in beef steers.

Rationale and Approach

Stocking rate can influence the profitability and performance of both rangeland and livestock. Adjustments in this metric can create differences in vegetative composition and diversity of rangeland over time.

At the South Dakota State University Cottonwood Field Station, a long-term grazing study has been conducted with three levels of grazing intensity (low = 0.32 AUM/acre, moderate = 0.40 AUM/acre, and high = 0.72 AUM/acre) since 1942, creating three distinct plant communities of rangeland vegetation—ranging from highly diverse (lightly grazed) to shortgrass-dominated (heavily grazed) (Dunn et al., 2010).

These differences have been shown to affect growth and performance during the stocker phase; however, little is known about how differences in growth during this phase affect subsequent carcass performance and value.

The objective of this research was to determine the influence of vegetative composition and diversity—driven by grazing history during the stocker phase—on carcass traits and economic returns of beef steers.

Yearling steers (n = 134, 116, 131 in 2020, 2021, 2022, respectively) were randomly assigned to the long-term grazing pastures. At the completion of the stocker phase, steers were weighed and transported to the Kansas State University Agricultural Research Center at Hays, KS, where they maintained their pasture groups for finishing.

Steers were harvested when estimated to achieve a compositional endpoint similar to industry standards. Hot carcass weight (HCW), backfat thickness, ribeye area (REA), marbling score, and USDA Quality and Yield grades were recorded. Production (HCW/acre) and economic return per carcass and per acre were calculated.

Findings

Stocking rate did not influence (P > 0.05) weight at the end of the stocker phase, carcass traits, or carcass value (Table 1). However, differences were detected between years (Table 2).

Steers were lighter (P < 0.001) in 2022 than in 2020 and 2021 and had greater (P < 0.001) HCW, backfat, yield grade, and marbling scores in 2021 compared to 2020 and 2022, while REA was similar (P > 0.05) in 2021 and 2022 but larger (P < 0.05) than in 2020.

Carcass value in 2020 was less (P < 0.001) than 2021 and 2022, which did not differ (P > 0.05). Stocking rate and year interacted (P < 0.01) for HCW (lb per acre) and carcass value per acre. Body weight produced per acre at the end of the stocker phase differed (P < 0.01) among all three treatments, with heavy stocking rate yielding the greatest and light stocking rate the least.

Hot carcass weight and value per acre increased (P < 0.01) as stocking rate increased, with the interaction caused by years; whether moderate stocking differed (P < 0.05) from light or heavy stocking.

Implications

Differences in vegetative composition driven by stocking rate did not carry over to impact carcass traits. However, heavier-stocked pastures returned greater overall beef production and economic value due to the increase in animals produced per unit of land. This demonstrates that stocking rate can influence the profitability of an operation without negatively affecting carcass quality.

References

Dunn, B. H., A. J. Smart, R. N. Gates, P. S. Johnson, M. K. Beutler, M. A. Diersen, and L. L. Janssen. 2010. Long-term production and profitability from grazing cattle in the northern mixed grass prairie. Rangeland Ecology & Management 63: 233–242.

Tables

Table 1. Least square means for stocking rate on live weight, carcass characteristics, and value

Table 2. Least square means for year effect on live weight, carcass characteristics, and value

Sourced from the South Dakota State University Animal Science Research Report 2024 © 2024 South Dakota Board of Regents.