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Amarillo, TX, United States

Rhoades M.B.,West Texas A&M University | Parker D.B.,U.S. Department of Agriculture | Cole N.A.,U.S. Department of Agriculture | Todd R.W.,U.S. Department of Agriculture | And 4 more authors.
Transactions of the ASABE | Year: 2010

Ammonia emissions from cattle feedlots pose the potential to react with other compounds such as oxides of nitrogen and sulfur, which lead to detrimental environmental effects. Ambient ammonia (NH 3) concentrations were measured continuously at a beef cattle feedyard for 12 months beginning in March 2007. Concentrations were measured every 5 min, 24 hours per day, at a sample intake height of 3.3 m using a chemiluminescence analyzer. On-site weather data were collected concurrently. Modeled emissions of NH 3 were compared with the mass balance of N for the feedyard. Mean annual NH 3 concentrations were 0.57 ppm, with a monthly average low of 0.37 ppm in December 2007 and a monthly average high of 0.77 ppm in August 2007. Flux densities were calculated using a backward Lagrangian stochastic model (WindTrax Mean annual flux density was 70.7 μg m -2 s -1 (2.2 kg m -2 year -1). Mean monthly flux density ranged from 42.7 to 123.1 μg m -2 s -1 (0.11 to 0.32 kg m -2 month -1) in November and April 2007, respectively. Both concentration and flux density had a diel distribution with minima during the nighttime hours and maxima during the early afternoon. On an annual basis, 48.8% of fed N was volatilized as NH 3. The inverse modeled daily ammonia production per head was 85.3 g NH 3-N (head fed) -1 d -1. © 2008 American Society of Agricultural and Biological Engineers. Source

Tolleson D.R.,University of Arizona | Carstens G.E.,Texas AgriLife Research Center | Welsh Jr. T.H.,Texas AgriLife Research Center | Teel P.D.,Texas AgriLife Research Center | And 4 more authors.
Journal of Animal Science | Year: 2012

Ticks are external parasites, which pose a significant economic burden to domestic animal agriculture. The effects of ticks on grazing animals may be exacerbated during periods of low nutrition, such as those encountered during drought. It is not completely understood how plane of nutrition and tick burden interact to affect metabolism in cattle. The objective of the current research was to examine the plane of nutrition by tick-burden interaction in cattle and determine the effects of this interaction on physiological indicators of growth and metabolism. Eight-month-old Angus cross steers (n = 28, 194 ± 3.0 kg) were stratified by pretrial BW and DMI into 1 of 4 groups (n = 7/group) in a 2 × 2 factorial arrangement. Categories were: moderate (14.0 ± 1.0% CP, 60 ± 1.5% TDN) vs. low (9.0 ± 1.0% CP, 58 ± 1.5% TDN) plane of nutrition and control (no tick) vs. tick treatment (300 pair of adult Amblyomma americanum per treated animal). Steers were individually fed their respective experimental diets ad libitum and feed intake was monitored for 35 d before and 21 d after the start of tick infestation (d 0). Blood samples were harvested via coccygeal venipuncture on d-7, 0, 7, 8, 9, 10, 11, 13, 17, and 21. Plasma cortisol and IGF-I were determined by RIA. Metabolic indicators were determined by colorimetric assay. Steers weighed 195 ± 6 kg on d-35, but on d-7 and d 21, the moderate steers weighed more than the low steers (244.1 ± 8.7 vs. 227.7 ± 8.4 kg, P < 0.07; and 283.4 ± 8.0 vs. 244.0 ± 7.9 kg, P < 0.001, respectively). Cortisol was affected by plane of nutrition and treatment (P < 0.08). Insulin-like growth factor-I was greater (P < 0.01) in moderate than in low and control animals (P < 0.02), compared with tick-treated animals. Tick treatment had no effect (P > 0.05) on any of the metabolites measured in this study. Plane of nutrition affected (P < 0.02) albumin, blood urea nitrogen, and glucose in that values from the moderate group animals were greater than those from the low group. Although cortisol was related to both tick treatment and nutritional status in the current study, with respect to the combination of parasitism and suboptimal nutrition, IGF-I was the most highly indicative constituent measured. Tick burden affected various characteristics of growth and metabolism in these growing cattle and the effects were exacerbated by a low plane of nutrition. © 2012 American Society of Animal Science. Source

Sakirkin S.L.P.,Texas Agri Life Research | Morgan C.L.S.,Texas A&M University | Auvermann B.W.,Texas Agri Life Research
Transactions of the ASABE | Year: 2010

Visible and near-infrared (VisNIR, 350-2500 nm) diffuse reflectance spectroscopy (DRS) may be a useful tool for determining crude ash content of solid cattle manure. However, the effect of sample preprocessing protocols on the predictive ability of the VisNIR-DRS models is unknown. In this study we explored the effects of drying and milling on the prediction of crude ash in feedyard manure using VisNIR-DRS. Samples (n = 120) of beef manure from open lots were evaluated for ash content by dry oxidation and then subjected to four preprocessing treatment protocols: oven-dried and milled, air-dried and milled, oven-dried and not milled, and air-dried and not milled. Each treatment protocol was used to calibrate partial least squares regression models for prediction of ash content by VisNIR-DRS. Two thirds of the samples were randomly selected to build calibration models, and the remaining third was used for validation. The root mean squared deviation (RMSD) and the ratio of the standard deviation over the RMSD (RPD) for each treatment were assessed to determine the best pretreatment protocol for ash determination of manure. The first derivative of the reflectance from air-dried, unmilled samples consistently generated the best predictive models with an RMSD of 5% crude ash (d.b.), an RPD of 2, and a bias of 0% crude ash (d.b.). © 2010 American Society of Agricultural and Biological Engineers. Source

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