Roger A. Eigenberg

Electrical conductivity monitoring of soil condition and available N with animal manure and a cover crop

Development of sustainable agricultural management systems will depend, in part, on the ability to better use renewable resources, such as animal manure, and to synchronize the levels of soil available N with crop plant needs during the growing season. This study was conducted at the US Meat Animal Research Center in the central USA to determine whether differences in electromagnetic (EM) soil conductivity and available N levels over a growing season can be linked to feedlot manure/compost application and use of a green winter cover crop. A series of soil conductivity maps of a research cornfield were generated using global positioning system (GPS) and EM induction methods. The study site was treated over a 7-year period with manure and compost at rates matching either the phosphorus or the nitrogen requirements of silage corn (Zea mays L.). The plot was split for sub-treatments of a rye (Secale cereale L.) winter cover crop and no cover crop. Image processing techniques were used to establish electrical conductivity (EC) treatment means for each of the growing season surveys. Sequential measurement of profile weighted soil electrical conductivity (EC a) was effective in identifying the dynamic changes in available soil N, as affected by animal manure and N fertilizer treatments, during the corn-growing season. This method also clearly identified the effectiveness of cover crops in minimizing levels of available soil N before and after the corn-growing season, when soluble N is most subject to loss. The EM method for assessing soil condition provides insights into the dynamics of available N transformations that are supported by soil chemical analyses. This real-time monitoring approach could also be useful to farmers in enhancing N use efficiencies of cropping management systems and in minimizing N losses to the environment.

Thermoregulatory profile of a newer genetic line of pigs

Researchers and producers alike have noted the increased susceptibility to heat stress exhibited by the newer genetic lines of pigs. A study was conducted to gather baseline information on the effects of acute heat stress on total heat production (THP), respiratory quotient (RQ), respiration rate (RR), and rectal temperature (Trectal) and to investigate the dynamic interaction of these parameters in growing–finishing barrows. Sixteen moderate–lean growth barrows were randomly assigned to a set of treatments as dictated by a repeated 4×4 Latin square crossover design. Pigs were moved from an individual pen to an indirect calorimeter where one of four environmental treatments (18, 24, 28, 32°C) were applied for 20 h. During the treatment exposure RR, THP, RQ and Trectal were measured. For the 2-week period between treatments, pigs were housed at thermoneutral (22°C). THP was found to be 17–20% higher than the published standards but comparable with other contemporary studies. Respiration rate was found to be a leading indicator of stress.

Thermoregulatory responses of feeder cattle

A study was designed to investigate the thermoregulatory responses of feeder cattle to both acute and chronic exposures to elevated environmental temperatures. Rectal temperatures (RT) and respiration rate (RR) showed significant differences between temperature treatments. Both RT and RR had a diurnal pattern, which followed the diurnal pattern of the ambient conditions with some lag. Heat production at thermoneutral conditions was significantly higher than at the heat stress treatments. Heat production and respiratory quotient were the only two parameters shown to change with acclimation to heat stress.

DEVELOPMENT OF A NEW RESPIRATION RATE MONITOR FOR CATTLE

Studies were conducted investigating bioenergetic responses of growing cattle to heat challenges using respiration rate as one of the primary measures. Respiration rate (RR) was measured using monitors designed from commercially available thin-film pressure sensors and a small battery powered micro-computer. The monitors were designed, fabricated, and tested to provide continuous records as a basis for evaluating stress responses associated with environmental conditions. This article provides details about the monitors and the suitability of obtained records as an indicator of stress, based on measures obtained in environmental chambers during constant and simulated heat wave conditions as well as a field study. Representative data from two laboratory studies indicated an association of RR and ambient temperature (P < 0.01) with diurnal changes being evident in the cyclic test and step changes being evident in the constant ambient temperature tests. A two to three breaths per minute (BPM) rate of change of RR with respect to ambient temperature (°C) was observed for steers in the laboratory studies. The field study revealed a striking response of RR to the ambient temperature (6.6 BPM/°C rate of change) for a steer that had direct solar load (no-shade) compared to a 1.6 BPM/°C rate of change in the shade.

SEASONAL AND SPATIAL VARIATIONS OF DENITRIFYING ENZYME ACTIVITY IN FEEDLOT SOIL

Animal waste models, used by producers to apply best management practices for waste control, are only crude approximations for nitrogen lost from the feedlot. Ammonia loss has been widely studied and accounts for the majority of gaseous nitrogen lost from a feedlot soil; however, denitrification has not been thoroughly investigated. The objectives of this study were to determine the seasonal denitrification enzyme activity (DEA) of a feedlot soil and evaluate potential controlling mechanisms. Electromagnetic mapping techniques were used to identify three locations within the feedlot pen. Three depths (unconsolidated surface material, 0–0.10 m, 0.10–0.20 m) were isolated at each location and analyzed for DEA, nitrification activity, denitrifier most probable number, soil moisture, pH, volatile solids, total carbon, and total nitrogen. Denitrification enzyme activity varied from 0.0 to 132.2 mmol gsoil –1 hr –1 based on season, depth, and spatial location. However, no single factor was perfectly correlated with DEA across all locations and depths. The seasonal average DEA of the unconsolidated surface material maintained significantly higher levels when compared to other depths. Downgradient surface materials maintained DEA levels greater than 60 mmol gsoil –1 hr –1 even when soil temperatures were near 0 ³ C. Also, the seasonal average DEA below 0.10 m for all locations was near zero during the entire investigation, significantly less than the other depths. We conclude that a range of environmental factors, alone or in conjunction, influence DEA depending upon location within the pen and soil depth.

Chapter 5: Thermal Indices and Their Applications for Livestock Environments

[First paragraphs]: Heat exchanges with the environment are crucial processes for maintaining homeothermy by humans and other animals. These exchanges involve heat production, conservation, and dissipation, and are dependent on both biological and physical factors. The complexity of these exchanges has led to many attempts to represent the environmental aspects by surrogate thermal indices as a basis for assessing the biological effect and consequent impact of the thermal environment. Resultant index values represent effects produced by the heat exchange process. For humans, comfort assessment is primary; for animals, assessing performance, health, and well-being have been foremost. Emphasis in this chapter is on thermal indices used in animal studies and their applications, with a view toward strategic and tactical decisions for rational environmental management. Illustrative examples are included, as are considerations for future efforts.

Links among Nitrification, Nitrifier Communities, and Edaphic Properties in Contrasting Soils Receiving Dairy Slurry

Soil biotic and abiotic factors strongly influence nitrogen (N) availability and increases in nitrification rates associated with the application of manure. In this study, we examine the effects of edaphic properties and a dairy (Bos taurus) slurry amendment on N availability, nitrification rates and nitrifier communities. Soils of variable texture and clay mineralogy were collected from six USDA-ARS research sites and incubated for 28 d with and without dairy slurry applied at a rate of ~300 kg N ha(-1). Periodically, subsamples were removed for analyses of 2 M KCl extractable N and nitrification potential, as well as gene copy numbers of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Spearman coefficients for nitrification potentials and AOB copy number were positively correlated with total soil C, total soil N, cation exchange capacity, and clay mineralogy in treatments with and without slurry application. Our data show that the quantity and type of clay minerals present in a soil affect nitrifier populations, nitrification rates, and the release of inorganic N. Nitrogen mineralization, nitrification potentials, and edaphic properties were positively correlated with AOB gene copy numbers. On average, AOA gene copy numbers were an order of magnitude lower than those of AOB across the six soils and did not increase with slurry application. Our research suggests that the two nitrifier communities overlap but have different optimum environmental conditions for growth and activity that are partly determined by the interaction of manure-derived ammonium with soil properties.

AN INEXPENSIVE LABORATORY AND FIELD CHAMBER FOR MANURE VOLATILE GAS FLUX ANALYSIS

Understanding the interactions between the environment and emissions from livestock manure is essential in developing management practices intended to minimize negative environmental consequences. However, protocols and equipment necessary to investigate these interactions at the laboratory or field-scale are cumbersome and can be expensive. An inexpensive dynamic flux chamber (cost <

Soil versus pond ash surfacing of feedlot pens: occurrence of Escherichia coli O157:H7 in cattle and persistence in manure.

400 per unit) was designed to measure gaseous emissions from cattle manure in laboratory and field experiments. The hemispherical stainless steel chamber (emission surface = 0.08 m2) was constructed with an internal gas mixing fan. A port was attached to the chamber top, which facilitated the collection of headspace gas samples for greenhouse gases and volatile organic compounds (VOC) by solid-phase microextraction (SPME). The chamber was tested to evaluate flow characteristics and was found to perform very similarly to a continuous-flow stirred reactor. As such, concentrations measured at the sampling port were indicative of concentrations anywhere in the headspace. In laboratory and field applications, the inexpensive dynamic flux chamber was easy to use and required little operator input to quickly obtain multiple samples to measure the relative emissions of greenhouse gases, ammonia (NH3), and VOC from multiple sites in cattle feedlot pens.

Status of soil electrical conductivity studies by central state researchers

Reducing Escherichia coli O157:H7 in cattle and their manure is critical for reducing the risk for human foodborne and waterborne illness. The objective of this study was to evaluate the effects of soil and pond ash surfaces for feedlot pens on the prevalence, levels, and/or persistence of naturally occurring E. coli O157:H7 and total E. coli in cattle (feces and hides) and manure. Cattle (128 beef heifers) were sorted among 16 pens: 8 surfaced with soil and 8 surfaced with pond ash. The prevalence of E. coli O157:H7 in feces decreased (P < 0.0001) during the study from 57.0% on day 0 to 3.9% on day 84 but did not differ (P > or = 0.05) between cattle on soil and on pond ash pens at any sampling period. The prevalence of the pathogen on hides and in feedlot surface material (FSM) also decreased (P < 0.0001), with no effect of soil or pond ash surface (P > or = 0.05). Similarly, levels of E. coli in FSM did not differ (P > or = 0.05) at any sampling period, and there were no clear trends for survival differences of E. coli O157:H7 or E. coli in FSM between pond ash and soil surfaces, although E. coli populations survived at 5.0 log CFU/g of FSM on the pen surfaces 6 weeks after the cattle were removed. These results indicate that housing cattle on pens surfaced with pond ash versus pens surfaced with soil does not affect E. coli O157:H7 in cattle or their manure.