Date of Graduation

5-2024

Document Type

Thesis

Degree Name

Master of Science in Animal Science (MS)

Degree Level

Graduate

Department

Animal Science

Advisor/Mentor

Shane Gadberry

Committee Member

Beth Kegley

Second Committee Member

James Mitchell

Third Committee Member

Daniel Rivera

Keywords

Fertilization; Forages; Stocker cattle; Supplementation; Tillage; Winter wheat

Abstract

The objectives for the two experiments were to determine the impact of nitrogen (N) fertilizer rate, establishment method through no-till (NT) or clean-till (CT), and supplementation on stocker, wheat stand, and economic performance. Within study 1, 24, 1.62-ha pastures, were used over a two-year period. Pasture treatments consisted of a combination of N fertilization rate (100.88, 134.5, or 168.12 kg/ha), applied as broadcast urea and split between two equal applications of 50% at planting and the remaining 50% in the spring when daytime average temperatures trend above 10°C, and of NT establishment or CT establishment. Steers were weighed on arrival, turnout, every 28 days, and when pulled off pasture. Steers were removed when forage mass became insufficient, temperatures became too cold to support regrowth, or when forage turned reproductive. Sample dates to determine forage mass and quality coincided with weigh dates. Pairwise comparisons using the Mixed Model in JMP were used to analyze treatment responses, with N rates, tillage method, and a N rate by tillage method interaction set as fixed effects, and year as a random effect. No-till pastures had trends (P ≤ 0.10) for greater final and mean forage mass, as well as reduced (P < 0.05) slope change in forage mass, indicating greater forage accumulation or retention. In the fall, CT pastures had greater (P < 0.05) grazing days, gain/ha, and final BW. This reversed in the spring, as NT produced greater (P < 0.05) grazing days, gain/ha, final BW, and ADG in the spring, and had greater (P < 0.05) combined gain/ha. Economic analysis mirrored steer performance, as CT produced greater (P < 0.05) fall income, and NT produced greater (P < 0.05) spring income, reduced establishment costs, reduced total costs, and greater total net returns. Nitrogen rate had little impact on steer, stand, and economic performance, but NT outperformed CT when spring grazing was implemented, resulting in an increase of net returns of $228.47/ha. Within study 2, an additional 6 NT pastures were fertilized with 100.88 kg N/ha and cattle supplemented with DDGS at 1% body weight as-fed. The Mixed Model procedure, followed by a Dunnett’s test was used to compare the 3 N rates without supplementation to the positive control of 100.88 kg N/ha rate with supplementation. Using year as a random effect. Supplemented pastures in the spring began with greater (P < 0.05) initial forage mass and produced greater (P < 0.01) mean and final forage mass, and greater slope change in forage mass. Supplementation of DDGS resulted in greater (P < 0.01) number of spring grazing days, gain/ha, final BW, and ADG. Greater (P < 0.01) calf management and feed costs resulted in the supplementation treatment having the greatest (P < 0.01) total cost/ha and the lowest (P < 0.01) net return/ha. Overall, results indicated that NT was economically more favorable than CT, N rates above the 100.88 kg/ha for the season were not warranted, and supplemental feed costs exceeded benefits of forage substitution.

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