EMI-Sensor Data to Identify Areas for Potential Emissions of Volatile Fatty Acids from Feedlot Surfaces

Remote-sensing methods have been developed that measure apparent soil conductivity (ECa) using electromagnetic induction (EMI). These methods have been adapted to measure manure accumulation on feedlot surface. The objectives of this study were to determine if EMI-sensor data could be used to predict differences in volatile fatty acids (VFA) and other volatiles produced on a feedlot surface three days following a high intensity rainfall event. A study was conducted where finishing steers in eight feedlot pens were fed either a corn- or wet distillers grains with solubles (WDGS)-based diet. The fermentation products formed during the microbial degradation of the accumulated manure on the pen surface were examined. Twenty soil samples were collected per pen using a response surface sampling procedure based on ECa values collected from the pen surface. The soil samples were incubated at room temperature for three days to determine differences in fermentation products formed due to varying diet. The fermentation products that were measured included straight- and branched-chained VFAs. These data were combined with EMI sensor data and GPS locations for each sample location to generate predictive models using multi-linear regression. The corn-based diet had greater average straight-chained VFA production than the WDGS diet. Alternately, the WDGS diet had greater branched-chained VFA production than the corn-based diet. This finding is similar with other research indicating that the higher content of carbohydrates commonly found in corn based diets tends to produce more straight-chained VFA. Consequently, the higher content of protein in the WDGS diet tended to produce more branch-chained VFAs. Grid maps were made based on the model-predicted production values and percent pen surface area contributing to specified concentration ranges. It was found that 65% of the corn base diet pen surfaces produced greater than 40 mmol kg1 straight-chained VFA while the WDGS pens only had 51% production for the same concentration range. The opposite trend was found for the branched-chained VFAs in that the corn-based diet had 47 % of the surface area produce 6 mmol kg-1 or greater while the WDGS diet had 61%. Diet appears to affect the types and amounts of VFAs produced three days following a high intensity rainfall event. The WDGS diet appears to produce higher branched-chained VFA, which can be considered more offensive. Understanding accumulation patterns and the ability to predict odorant production can be used to develop precision management practices to mitigate contamination from animal feeding operations.