164 Effect of distillers grains supplementation and fertilization rate on performance of stocker cattle grazing wheat pasture and stand performance

Abstract Within this study, the objectives were to determine how varied Nitrogen (N) fertilization rates and inclusion of dried distiller’s grains plus solubles (DDGS) impacted stocker and wheat stand performance within a no-till (NT) production system. A total of twenty-four 1.62-ha pastures were split between 3 unsupplemented treatments with urea spread at fixed rates of 50.44, 67.25, 84.06 kg N/ha in autumn and again in spring along with an additional 6 pastures fertilized with 50.44 kg N/ha each growing season plus supplemented with DDGS. From fall of 2021 to Spring of 2023, 576 beef steers (286.62 ± 36.67 kg) were randomly allocated at fixed stocking rates of 2.47 steers/ha (4 steers/pasture) in the fall, and 4.94 steers/ha (8 steers/pasture) in the spring. Steers were weighed upon arrival, at turnout, every 28 d, and when pulled off pasture. Steers were pulled off pasture when forage mass (FM) became insufficient, temperatures became too cold to support regrowth, or forage entered reproductive phase. Sampling dates to determine forage mass and quality coincided with weigh dates, where 20 plate meter readings were taken in every field and were recorded with a 0.25m2 plate meter, and 0.25m2 grass clippings were obtained from 15 fields every sampling date to estimate FM. Pairwise comparisons using the Mixed Model procedure in JMP were used to analyze data, with N rates with and without supplementation as a single fixed categorical variable, and year modeled as a random effect. In the fall, supplemented pastures produced greater ADG than 67.25 and 84.06 kg N/ha pastures (P 0.05), along with greater total costs of supplemented pastures compared with all unsupplemented treatments (P 0.0001). In the spring, supplemented pastures produced greater end weights, gain per hectare, forage mass and ADG than all unsupplemented treatments (P 0.0001), and supplementation provided more grazing days (P 0.05). While total sale income for supplemented pastures were greater than all unsupplemented treatments (P 0.05), total costs of supplemented pastures were all increased (P 0.0001), resulting in less income after variable costs (P 0.0002). Response changes to supplementation were more pronounced than responses to increased fertilization. In conclusion, these results indicate that DDGS supplementation provided greater performance benefits to stocker cattle grazing wheat pasture than increased N fertilization rate, but the added costs associated with feeding resulted in lower profitability. However, the addition of DDGS supplementation may provide an opportunity to increase stocking rates to potentially improve profitability.