N. Andy Cole

Preconditioning Calves for the Feedlot

Preconditioning is a theoretically sound concept; however, it has not gained wide acceptance by cow-calf producers or feeders owing to logistics and expense. Many of the claims of preconditioning are not substantiated by controlled research data. Many of the positive claims made for preconditioning may be a result of the calves moving more rapidly through the marketing channels. Although preconditioning is profitable to some producers, on the average, preconditioning is difficult to justify economically. Modifications of the preconditioning concept have the potential to make it more feasible to the majority of cow-calf producers. Any producer or feeder considering a preconditioning program or feeding preconditioned calves should first calculate an economic projection.

Recovery of agricultural odors and odorous compounds from polyvinyl fluoride film bags.

Accurate sampling methods are necessary when quantifying odor and volatile organic compound emissions at agricultural facilities. The commonly accepted methodology in the U.S. has been to collect odor samples in polyvinyl fluoride bags (PVF, brand name Tedlar®) and, subsequently, analyze with human panelists using dynamic triangular forced-choice olfactometry. The purpose of this research was to simultaneously quantify and compare recoveries of odor and odorous compounds from both commercial and homemade PVF sampling bags. A standard gas mixture consisting of p-cresol (40 μg m−3) and seven volatile fatty acids: acetic (2,311 μg m−3), propionic (15,800 μg m−3), isobutyric (1,686 μg m−3), butyric (1,049 μg m−3), isovaleric (1,236 μg m−3), valeric (643 μg m−3), and hexanoic (2,158 μg m−3) was placed in the PVF bags at times of 1 h, 1 d, 2 d, 3 d, and 7 d prior to compound and odor concentration analyses. Compound concentrations were quantified using sorbent tubes and gas chromatography/mass spectrometry. Odor concentration, intensity, and hedonic tone were measured using a panel of trained human subjects. Compound recoveries ranged from 2 to 40% after 1 h and 0 to 14% after 7 d. Between 1 h and 7 d, odor concentrations increased by 45% in commercial bags, and decreased by 39% in homemade bags. Minimal changes were observed in intensity and hedonic tone over the same time period. These results suggest that PVF bags can bias individual compound concentrations and odor as measured by dynamic triangular forced-choice olfactometry.

Nutrition and Disease

Mortality from digestive diseases in feedlot cattle is second only to that from respiratory diseases. Acidosis and bloat are the major digestive disorders and are likely to continue because of ongoing attempts to improve the efficiency of beef production by feeding more grain and less roughage. Subacute acidosis is probably the most prevalent form of acidosis in feedlots and is difficult to diagnose because of the absence of overt clinical signs. Ruminal changes in subacute acidosis are not as dramatic as those in acute acidosis. Also, the subacute form is not severe enough to induce systemic acidosis. Ruminal acidosis is also a predisposing factor for many other ailments in feedlot cattle such as laminitis, polioencephalomalacia, sudden death syndrome, and liver abscesses. Control of acidosis is achieved largely by sound nutritional management. Antimicrobial compounds (i.e., ionophores and nonionophores), have become management tools to impart stability to ruminal fermentation, modulate feed intake, and control acidosis. Bloat in feedlot cattle can be of free gas or frothy type. Frothy bloat is more common but is rarely the reason for bloat deaths. The economic impact of bloat results mainly from decreased animal performance. The etiology of bloat is complex and is the result of interactions between three major groups of factors: animal, dietary, and microbial. Presently, an effective method to control frothy bloat in feedlot cattle is not available. Ionophore antibiotics, particularly monensin, have been shown to be effective in decreasing the incidence and severity of bloat in cattle.

Use of Fat and Zeolite to Reduce Ammonia Emissions from Beef Cattle Feedyards

Ammonia emissions from cattle feedyards may comprise 40% or more of nitrogen intakes. Decreasing ammonia emissions would improve the fertilizer value of feedyard manure and decrease potential adverse effects on the environment. Two trials were conducted to evaluate the effects of fat and zeolite on potential ammonia emissions from a feedlot surface. In the first trial corn oil, alum, a urease inhibitor, or potassium zeolite were added to simulated feedlot surfaces in lab-scale chambers and ammonia losses were captured using an acid solution. In trial two, five beef steers were fed one of five finishing diets (0% added fat, 3% added fat, 6% added fat, 3% fat+1% zeolite, or 3% fat+2% zeolite) in a 5 x 5 Latin square. During the last 5 days of each period feces and urine output were collected in stalls to determine nutrient digestion and retention. Feces and urine from each steer were used in the lab-scale flow-through chambers to estimate potential ammonia losses. In trial 1, zeolite and fat additions decreased ammonia losses by 51 to 86%; however the effects were not additive. In trial 2, apparent protein digestion, nitrogen retention, and nitrogen excretion were not affected by dietary fat or zeolite. In vitro ammonia losses were not significantly affected by dietary zeolite; however in vitro ammonia losses were greater (P < 0.05) when steers were fed diets containing no added fat. These results suggest that fat and zeolites can potentially decrease ammonia emissions from beef cattle feedyards.

Knowledge and tools to enhance resilience of beef grazing systems for sustainable animal protein production

Ruminant livestock provides meat and dairy products that sustain health and livelihood for much of the worlds population. Grazing lands that support ruminant livestock provide numerous ecosystem services, including provision of food, water, and genetic resources; climate and water regulation; support of soil formation; nutrient cycling; and cultural services. In the U.S. southern Great Plains, beef production on pastures, rangelands, and hay is a major economic activity. The regions climate is characterized by extremes of heat and cold and extremes of drought and flooding. Grazing lands occupy a large portion of the regions land, significantly affecting carbon, nitrogen, and water budgets. To understand vulnerabilities and enhance resilience of beef production, a multi‐institutional Coordinated Agricultural Project (CAP), the “grazing CAP,” was established. Integrative research and extension spanning biophysical, socioeconomic, and agricultural disciplines address management effects on productivity and environmental footprints of production systems. Knowledge and tools being developed will allow farmers and ranchers to evaluate risks and increase resilience to dynamic conditions. The knowledge and tools developed will also have relevance to grazing lands in semiarid and subhumid regions of the world.

Flux-Gradient Estimates of Ammonia Emissions from Beef Cattle Feedyard Pens

Concentrated animal feeding operations are major sources of ammonia emitted to the atmosphere. There is a considerable literature on ammonia emissions from poultry and swine, but few studies have investigated large, open lot beef cattle feedyards. We used the micrometeorological flux-gradient method to estimate ammonia emissions during six field campaigns in three seasons. Profiles of ammonia, wind speed and air temperature were measured on towers located within feedyard pens. Atmospheric ammonia concentration was measured using either acid gas washing or chemiluminescence. Mean daily ammonia flux in summer averaged 72 µg m-2 s-1, and in winter, 39 µg m-2 s-1. Springtime fluxes were highly variable and averaged 79 µg m-2 s-1; high springtime fluxes were attributed to greater ammonium concentration in manure and high wind speeds. Ammonia-N emisson rate averaged 3930 and 2150 kg d-1 in summer and winter, respectively, which was 45% and 27% of fed N. Assuming that the mean of summer and winter emission rates represented a mean annual emission, ammonia-N loss was 36% of fed N, and an annual emission factor for feedyard pens based on total yearly per head production was 11.0 kg NH3-N head-1 yr-1. Ammonia emissions increased after N in cattle rations was increased from 13.5% to 14.5%. Ammonia emissions estimated using the flux-gradient method were 22 to 36% less than those derived from an inverse dispersion model. Uncertainty in the Schmidt number and possible violation of the assumption of homogeneous flow could have contributed to the lower flux estimates of the flux-gradient method. Optimizing fed N through practices such as phase feeding could help minimize ammonia emissions. Longer term, more continuous monitoring of ammonia emissions is needed to better define annual variability, emission rates and factors, and facilitate development of process models.

Factors Affecting Emission Measurements with Surface Isolation Flux Chambers

We conducted field experiments to evaluate how factors such as sweep air flowrate, time since urine deposition, and flux chamber footprint area affect ammonia fluxes from open-lot feedyard and dairy surfaces as measured using three different flux chamber designs. The chambers included a 26.5-cm diameter chamber (North Carolina State University design), a 49-cm diameter chamber (EPA-type design), and a 1.2 m x 2.4 m rectangular chamber (West Texas A&M University design). Clean sweep air collected upwind of the feedyard (<50 ppb NH3-N) was supplied to the chambers using a large compressed air tank, and ammonia concentrations were measured using a Thermo Environmental Instruments 17C chemiluminescence NH3 analyzer. Ammonia fluxes increased up to 10-fold between sweep airflow rates of 0.1 and 1.0 volumetric changes per minute. Ammonia fluxes from urine spots were highly dependent on the time since the urine was excreted. In one instance, the flux decreased at 57 ug/m2/min for every minute elapsed during the first two hours after excretion. Maximum fluxes and variability among individual flux measurements decreased with increasing flux chamber footprint area. A better knowledge of how these factors affect calculated emission rates will be beneficial to future development of emission factors for open-lot feedyards and dairies.

Effect of Wind Tunnel Air Velocity on VOC Flux Rates from CAFO Manure and Wastewater

Wind tunnels and flux chambers are often used to measure volatile organic compound (VOC) emissions and estimate emission factors from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission rates. VOC emissions were measured on standard solutions of VOCs in water, and on manure and wastewater from beef cattle and dairy AFOs at wind tunnel air velocities between 0.003 and 0.2 m/s corresponding to volumetric air exchange rates of 0.6 to 39 exchanges per minute. Activated-carbon-filtered air was passed through a small rectangular wind tunnel (30.5 cm length, 15.2 cm width, 5.1 cm height). Outlet air was sampled using stainless steel sorbent tubes (Tenax® TA) and analyzed for seven volatile fatty acids (acetic, propionic, isobutyric, butyric, isovaleric, valeric, hexanoic) and four heavier molecular weight (MW) semi-VOCs (phenol, p-cresol, indole and skatole) using gas chromatography/mass spectrometry. VOC emission rates increased linearly with increasing wind velocity. These results show that wind velocity is a major factor affecting VOC emissions from AFOs. Selection of representative air velocity or sweep air flow rate is critical when estimating VOC emission factors using wind tunnels and flux chambers.

Ammonia Concentration and Modeled Emission Rates from a Beef Cattle Feedyard

Ambient NH3 concentrations were measured at a beef cattle CAFO during the spring and summer months of 2007. Concentrations were measured every five minutes, 24-hours per day at a sample intake height of 3.3 m using a chemiluminescence analyzer. On site weather data was collected concurrently. Emission rates were estimated using a backward Lagrangian Stochastic model (WindTrax 2.0.7.8). Mean 24-hr concentrations for spring were 0.498, 0.597 and 0.568 ppm for March, April and May, respectively. Corresponding fluxes for March, April and May were 57.76, 123.10 and 86.34 µg m-2 sec-1, respectively. Summer mean ambient concentrations were 0.684, 0.702 and 0.568 ppm for June, July and August, respectively. Summer fluxes were 85.27, 75.06 and 71.56 µg m-2 sec-1 for June, July and August, respectively.

Estimation of Ammonia and Hydrogen Sulfide Emissions from Cattle Feedlots in Texas

A dynamic flow-through chamber system and continuous analyzers were used for on-site measurements of ammonia-nitrogen (NH3-N) and hydrogen sulfide-sulfur (H2S-S) fluxes from commercial feedlot surfaces in northwestern Texas during two week period in the summer of 2002. Manure pack moisture content, pH, and TKN were measured daily to characterize its relation with NH3-N fluxes. The preliminary average NH3-N and H2S-S flux from the feedlot surface were 1,669 ± 1,212 NH3-N µg/m2/min and 1.884 ± 1.497 H2S-S µg S/m2/min. Manure pack temperature and TKN was found to have a weak correlation with NH3-N flux.