Influence of Reduced Nitrogen Diets on Ammonia Emissions from Cattle Feedlot Pens

Field pea can replace soybean meal-corn mixtures in the fattening concentrate of young bulls improving the digestibility

The inclusion of pea (Pisum sativum) in the fattening concentrate at 0%, 15%, 30%, and 45% as a replacement for soybean meal and corn was evaluated on in vitro and in vivo digestibility studies of young Parda de Montaña bulls. In the in vitro trial, gas production was determined with an Ankom system for 48 h. The 30%pea and 45%pea concentrates increased the organic matter (OM) degradability, the ammonia-N content and the ratio of acetic:propionic, with no effect on gas production, final ruminal pH and total volatile fatty acid production. In the in vivo assay, 4 young bulls (initial weight 251 ± 4 kg) received restricted amounts of concentrates plus straw during 4 consecutive experimental periods. No differences in intake were observed and 30%pea and 45%pea had higher digestibility of crude protein (CP), and OM than the rest of treatments. The nitrogen intake increased linearly with the inclusion of pea with similar nitrogen urinary and faecal excretions, and the nitrogen retained was greater in 30%pea and 45%pea than the rest of treatments. The plasma concentrations of IGF-1, total protein, β-hydroxybutyrate and urea at the beginning and at the end of each period were not affected by the inclusion of pea. In conclusion, the total replacement of soybean-corn mixtures by pea in the fattening concentrate of bulls could be recommended as it improved the CP digestibility and nitrogen retention.

Development of an equation to predict net protein requirements for the growth of Zebu beef cattle

The accurate estimation of protein requirements for beef cattle is a key factor in increasing livestock profitability and decreasing the environmental impacts of excessive N excretion due to mismatching between assumed requirements and diet formulation. A meta-analysis was conducted to evaluate and validate a new equation to predict the net protein requirements for growth (NPg) of Zebu beef cattle. For the development of the new approach, a database of 552 observations comprised of bulls, steers, and heifers of different genetic groups (Zebu, beef crossbreed, and dairy crossbreed) was assembled. The new approach was evaluated and compared to current models devised by the international nutrient requirements system committees (Agricultural Research Council, 1980; Beef Cattle Nutrient Requirements Model, 2016; BR-CORTE, 2016) to predict NPg. The model evaluation was performed through the model evaluation system (version 3.1.16) using an independent data set (n = 177 observations). An equation was considered the best estimator of NPg if the following conditions were met: (1) the intercept and slope of the regression between ordinary residues and/or predicted NPg values must have been equal to zero and one, respectively; and (2) the greatest concordance correlation coefficient (CCC) and determination coefficient (R), and lowest mean squared error of prediction (MSEP) were attained. Based on the regression models of the observed v. predicted NPg of Zebu beef cattle, both the new approach and that of the ARC (1980) correctly estimated NPg, since the intercept and slope were not different (P > 0.05) from zero and one, respectively. Additionally, the new approach's determination coefficient was the greatest and the closest to one. The fact that the new model achieved a higher CCC and lower MSEP than the existing models indicated its superior reproducibility and accuracy. The equations proposed by BR-CORTE (2016) and the BCNRM (2016) did not correctly estimate NPg in that the intercept and slope were different (P < 0.01) from zero and one, respectively. Thus, the equations proposed by the new approach and the ARC (1980) accurately and precisely estimated NPg and are recommended for Zebu cattle. Furthermore, the inclusion of equivalent empty BW (EQEBW) in the new approach improves the estimation of NPg. We suggest the use of the following equation to calculate NPg for Zebu beef cattle: NPg = 176.01 × EBG - 0.381 × EQEBW0.75 × EBG1.035 (R = 0.80 and CCC = 0.75); where NPg = net protein requirements for growth, EBG = empty body gain, and EQEBW = equivalent empty BW.

Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots

Formulating diets conservatively for minimum crude-protein (CP) requirements and overfeeding nitrogen (N) is commonplace in grain finishing rations in USA, Canada and Australia. Overfeeding N is considered to be a low-cost and low-risk (to cattle production and health) strategy and is becoming more commonplace in the US with the use of high-N ethanol by-products in finishing diets. However, loss of N from feedlot manure in the form of volatilised ammonia and nitrous oxide, and nitrate contamination of water are of significant environmental concern. Thus, there is a need to improve N-use efficiency of beef cattle production and reduce losses of N to the environment. The most effective approach is to lower N intake of animals through precision feeding, and the application of the metabolisable protein system, including its recent updates to estimation of N supply and recycling. Precision feeding of protein needs to account for variations in the production system, e.g. grain type, liveweight, maturity, use of hormonal growth promotants and β agonists. Opportunities to reduce total N fed to finishing cattle include oscillating supply of dietary CP and reducing supply of CP to better meet cattle requirements (phase feeding).

Ammonia Emissions from Subalpine Forest and Mountain Grassland Soils in Rocky Mountain National Park

Atmospheric deposition of NH and NH contributes to eutrophication within sensitive subalpine ecosystems of Rocky Mountain National Park (RMNP) in the United States. However, little is known about the local contribution of NH from soils within the park. Thus, the goal of this study was to quantify and compare NH emissions from intact soil cores sampled from a subalpine grassland and forest within RMNP. Cores were collected at 2-wk intervals from 20 June 2011 to 12 Sept. 2011 and transferred to a laboratory chamber system for NH flux measurements. Additionally, N wet deposition was monitored at the sampling location to investigate possible impacts on NH soil emissions. The average quantifiable NH emissions (with SDs) from intact soil cores analyzed in the laboratory (23°C) were 0.42 ± 0.30 mg NH-N m d for grassland soil and 0.21 ± 0.03 mg NH-N m d for forest soil ( < 0.001). A mechanistic model was developed to estimate the impact of temperature on soil emissions using the chamber data and field-site air temperatures. Average estimated NH emissions from the field site over the study period were 0.21 and 0.082 mg NH-N m d for grasslands and forests, respectively. Ammonium wet deposition was not correlated to short term reemission of NH based on N isotope analysis. This work provides new information on the magnitude of NH emissions from native subalpine soils, indicating that natural emissions are not likely major sources of NH in the RMNP airshed.

Emission of volatile organic compounds after land application of cattle manure

Beef cattle manure can serve as a valuable source of nutrients for crop production. However, emissions of volatile organic compounds (VOCs) after land application may pose an odor nuisance to downwind populations. This study was conducted to evaluate the effects of land application method, diet, soil moisture content, and time since manure application on VOC emissions. Manure was collected from feedlot pens where cattle were fed diets containing 0, 10, or 30% wet distillers grains with solubles (WDGS). Land application methods included surface-applying manure (i.e., no-tillage) or incorporating manure using disk tillage. The effects of soil moisture content on VOC emissions was determined by adding water to each of the plots approximately 24 h after manure application. Isovaleric acid, butyric acid, and 4-methylphenol contributed 28.9, 18.0, and 17.7%, respectively, of the total measured odor activity values. In general, the largest emissions of volatile fatty acids and aromatics were measured during the initial collection periods on the no-tillage plots under dry soil moisture conditions. Emissions of volatile fatty acids and aromatics were reduced after water additions because these compounds were stored in the soil-water matrix rather than released into the atmosphere. In contrast, sulfide emissions generally increased with the addition of the water, especially on the plots containing manure from the 30% WDGS diet. Sulfur content of manure increases with higher percentages of WDGS feed stock. Application method, diet, soil moisture content, and time since application should be considered when estimating VOC emissions.