Southern Illinois Soybean Varieties: Implications for Relative Livestock Feed Value Scores, Modeled Soybean Meal Values, and Livestock Diet Formulation.

The research evaluated how location, crop year, relative maturity, and nutrient composition affect modeled soybean meal (SBM) values and the relative livestock feed value (LFV) scores of soybean varieties grown in southern Illinois. The study also assessed the impact of non-ruminant-specific LFV scores and modeled SBM composition in ruminant diets on requirements for other feed ingredients, such as feed corn. Among 47 soybean varieties collected from two southern Illinois locations over two growing seasons, modeled SBM values ranged from US$340.0 to US$370.0 per ton, while relative LFV scores varied from 1.3 to 9.9. SBM inclusion in the modeled backgrounding beef cattle diets ranged from 331.8 kg to 367.1 kg/ton, and feed corn inclusion ranged from 82.4 kg to 117.6 kg/ton. The feed formulation model showed a positive association for soybean seed protein with methane (CH₄) emissions (r = 0.94 for CH₄ as % GE, r = 0.98 for CH₄ in mol/d, and r = 0.89 for CH₄ in Mcal/d), though the relative range in predicted CH₄ emissions from the feed formulations was only 1.8%, suggesting minimal impact of soybean varieties and limited practical significance. The feed formulation model showed a positive association between corn demand and dietary CP concentrations (R² = 0.85). Meal from superior soybean seeds is predicted to be required at lower inclusions in model ruminant diets to achieve a net positive metabolizable protein balance.