On-Farm Uncontrolled Steeping and Cooling of Roasted Soybeans: Measuring Heat Exposure and Implications for Protein Value

Soybeans are widely used in dairy cattle diets, and on-farm roasting is a common practice to improve protein utilization. However, current processing recommendations were developed decades ago under controlled conditions and may not reflect modern dairy systems using high-oleic soybeans and mobile roasting equipment. Across dairy farms, there is substantial variation in post-roasting practices, particularly in steeping and cooling. In many cases, soybeans remain at elevated temperatures for extended periods without controlled cooling, which can reduce protein digestibility, decrease milk production, and effect nitrogen levels.

The objective of this proposal is to determine how uncontrolled steeping and cooling after roasting affects soybean protein quality and nutritional value, and to develop practical recommendations to improve processing consistency. Specifically, we aim to quantify how long soybeans are exposed to high temperatures after roasting and evaluate how this exposure influences rumen-undegradable protein, protein digestibility, dairy cow performance, and economic returns.

To achieve these objectives, the study will be conducted on commercial dairy farms in Pennsylvania that utilize on-farm soybean roasting. Temperature data loggers will be placed in soybean storage containers to monitor heat dissipation following roasting. Soybean samples will be collected and analyzed using laboratory assays and in situ rumen incubation techniques to assess protein degradability and digestibility. In addition, farm-level data, including milk production and milk composition, will be collected to evaluate impacts on animal performance and nitrogen use efficiency. Economic analyses will be conducted to assess the financial implications of different processing practices.

Results from this project will be shared through a comprehensive outreach program. This includes on-farm demonstration events, extension publications, and a practical decision-support guide to help farmers and nutritionists evaluate soybean processing practices. Findings will also be presented at regional workshops and industry meetings, including the Penn State Dairy Nutrition Workshop. By improving the consistency and effectiveness of soybean processing, this project will help dairy producers enhance nutrient use efficiency, improve nitrogen levels, and improve farm profitability through better utilization of homegrown feeds.

Objective 1. Quantify post-roasting heat exposure under on-farm conditions: Measure the duration and intensity of temperature exposure of roasted soybeans during uncontrolled steeping and cooling using temperature data loggers.

Objective 2. Evaluate the effects of post-roasting heat exposure on soybean protein quality: Determine how variation in steeping and cooling duration affects rumen undegradable protein (RUP), protein degradability kinetics, protein digestibility, and indicators of heat damage (e.g., ADIN, NDIN, PDI, urease activity).

Objective 3. Assess the impact of soybean processing variability on dairy cow performance and nitrogen use efficiency:Quantify relationships between processing conditions and milk production, milk composition, and nitrogen utilization at the farm level.

Objective 4. Evaluate the economic implications of controlled vs. uncontrolled steeping and cooling: Estimate income over feed costs (IOFC) and determine whether controlled steeping and cooling represents a cost or an economic benefit to dairy farms.

Objective 5. Develop practical, science-based recommendations for soybean processing in dairy systems: Integrate biological, on-farm, and economic data to generate guidelines that improve feed consistency, nutrient utilization, and profitability.

These objectives address the key research question: how does uncontrolled post-roasting heat exposure affect soybean protein value and dairy system performance under real-world farm conditions?