Lab-scale model to evaluate odor and gas concentrations emitted by deep bedded pack manure

Authors: Spiehs, Mindy

Submitted to: Journal of Visualized Experiments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2018
Publication Date: 7/19/2018
Publication URL: http://handle.nal.usda.gov/10113/6086604
Citation: Spiehs, M.J. 2018. Lab-scale model to evaluate odor and gas concentrations emitted by deep bedded pack manure. Journal of Visualized Experiments. 137:e57332. https://doi.org/10.3791/57332.
DOI: https://doi.org/10.3791/57332

Interpretive Summary: There is an increasing number of beef cattle producers in the Midwest and Upper Great Plains raising cattle in confinement facilities. Some of these confinement facilities use substantial amounts of bedding which forms a bedded pack of bedding and manure. The bedded pack may be retained until the cattle are shipped to market or it may be retained through several groups of cattle. The most common bedding material used in these studies is corn stalks, but the demand for bedding may make it difficult for producers to have sufficient quantities of corn stalks. Producers are interested in alternative bedding materials but question how the use of other bedding materials would impact the environment of the facility, including the production of odorous gases and the nutrient composition of the resulting bedded pack which will eventually be removed from the barn and used as crop fertilizer. Conducting an on-farm trial to test all available bedding materials would be costly. Not only would it be difficult to repeat the study multiple times needed to obtain quality data, but it is difficult to control variables such as weather, age of cattle, and diets fed to cattle when conducting on-farm studies. There was a need to develop a lab-scaled bedded manure pack that could be used to simulate a commercial-sized farm so research could be conducted economically in a controlled environment. Researchers at USMARC developed a protocol for lab-scaled simulated bedded packs that are maintained in 10-gallon plastic trash cans. Odors and gases are measured from the air above the simulated bedded packs and the nutrient composition of the bedded packs can be analyzed to determine the fertilizer value of the bedded pack. Seven manuscripts have been published using this methodology. The results verify that the lab-scale model not only has similar physical and chemical characteristics to a bedded pack in a commercial barn (such as temperature, pH, and nitrogen content), but that researchers were able to detect significant differences between bedding materials using as few as 8 simulated bedded packs per treatment. While not a perfect simulation of “real-world” conditions, the simulated bedded packs serve as a good model for researchers to use to examine treatment differences among bedded packs and to conduct preliminary research before conducting an on-farm study.

Technical Abstract: A lab-scaled simulated bedded pack model was developed to study air quality and nutrient composition of deep-bedded packs found in cattle monoslope facilities. This protocol has been used to effectively evaluate many different bedding materials, environmental variables (temperature, humidity), and potential mitigation treatments that can improve air quality in commercial deep-bedded monoslope facilities. The model is dynamic and allows researchers to easily collect many chemical and physical measurements from the bedded pack. Weekly measurements collected over the course of six to seven weeks, allows sufficient time to see changes in air quality measurements over time as the bedded pack mature. The data collected from the simulated bedded packs is within the range of concentrations previously measured in commercial deep-bedded monoslope facilities. Past studies have demonstrated that that 8 – 10 experimental units per treatment are sufficient to detect statistical differences among the simulated bedded packs. The bedded packs are easy to maintain, requiring less than 10 minutes of labor per bedded packs per week to add urine, feces, and bedding. Sample collection using the gas sampling system requires 20-30 minutes per bedded pack, depending on the measurements that are being collected. The use of lab-scaled bedded packs allows the researcher to control variables such as temperature, humidity, and bedding source that are difficult or impossible to control in a research or commercial facility. While not a perfect simulation of “real-world” conditions, the simulated bedded packs serve as a good model for researchers to use to examine treatment differences among bedded packs. Several lab-scale studies can be conducted to eliminate possible treatments before trying them in a research or commercial-sized facility.