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On-farm methane (CH 4 ) emissions need to be estimated accurately so that the mitigation effect of recommended practices can be accounted for. In the present study prediction equations for enteric CH 4 have been developed in lieu of expensive animal measurement approaches. Our objectives were to: (1) compile a dataset from individual beef cattle data for the Latin America and Caribbean (LAC) region; (2) determine main predictors of CH 4 emission variables; (3) develop and cross-validate prediction models according to dietary forage content (DFC); and (4) compare the predictive ability of these newly-developed models with extant equations reported in literature, including those currently used for CH 4 inventories in LAC countries. After outlier's screening, 1100 beef cattle observations from 55 studies were kept in the final dataset (∼ 50 % of the original dataset). Mixed-effects models were fitted with a random effect of study. The whole dataset was split according to DFC into a subset for all-forage (DFC = 100 %), high-forage (94 % ≥ DFC ≥ 54 %), and low-forage (50 % ≥ DFC) diets. Feed intake and average daily gain (ADG) were the main predictors of CH 4 emission (g d -1 ), whereas this was feeding level [dry matter intake (DMI) as % of body weight] for CH 4 yield (g kg -1 DMI). The newly-developed models were more accurate than IPCC Tier 2 equations for all subsets. Simple and multiple regression models including ADG were accurate and a feasible option to predict CH 4 emission when data on feed intake are not available. Methane yield was not well predicted by any extant equation in contrast to the newly-developed models. The present study delivered new models that may be alternatives for the IPCC Tier 2 equations to improve CH 4 prediction for beef cattle in inventories of LAC countries based either on more or less readily available data., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The objective was to evaluate a method to reduce the calcium nitrate release rate in a simulated rumen fermentation environment, and to determine its effect on dry matter degradation and methane production. In the in vitro experiment, kikuyu grass (Cenchrus clandestinus, Hochst ex Chiov) (KK) was used as the base feed and the addition of protected nitrate (PN), free nitrate (FN) and urea (KU) to the fermentation environment. The amount of nitrate added corresponded to 3 % of the incubated dry matter. The data were analyzed with repeated measures over time considering treatment and time as fixed effects and the rumen inoculum donor animal as a random factor. After 24 h of incubation, FN and PN reduced dry matter degradation by 11.4 and 15 %, respectively. The addition of nitrate significantly reduced methane production. The difference in methane production rates expressed in ml/g of degraded dry matter between the FN (21.0) and PN (31.2) treatments at 48 h of incubation indicates a lower nitrate release rate as a consequence of the protection method employed. The results of this trial show that the inclusion of protected nitrates at levels corresponding to 3 % of the incubated dry matter can reduce methane production by 53 %. [ABSTRACT FROM AUTHOR]

The main objectives of this study are to determine the emission of greenhouse gases based on the amount of nitrogen applied to soil from bovine manure and to generate their emission factors. The treatments consist of applying one or two kilograms of manure and one or two liters of urine, resulting in the application of 56.11, 112.23, 104.90, and 209.80 g N/m2, in addition to a control treatment. Gas emissions are determined during the first 39 days by using static cameras. The methane emission factors are 0.25 and 0.53 kg/animal/year after applying one and two kilograms of manure, respectively. In addition, increasing the dose of urine, from one to two liters, decreases the amount of nitrogen that is converted into nitrous oxide from 2.1% to 1.24%. In conclusion, applying bovine feces instead of urine (proportional to the N dose applied) increases the production of CO2eq, resulting in greater environmental contamination. [ABSTRACT FROM AUTHOR]

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The objective of this study was to evaluate the effect of the mixture of different ratios of kikuyu grass (Pennisetum clandestinum) (K) -- potato (Solanum tuberosum) (P) on methane production in vitro, during the second semester of 2012 in the University Research Center (Medellín, Colombia). The treatments consisted of mixtures K/P in ratios of 100/0 (T1), 75/25 (T2) and 50/50% (T3). The results were processed through a repeated measures analysis over time and nonlinear regression. At the end of incubation period (between 0 and 48 hours), the cumulative gas production (ml/g MSi), the cumulative methane production (ml/g MSi) and the dry matter digestibility were statistically differents (p<0.05) among all treatments, increasing with higher levels of potato in the mixture. In the same time interval, the relationship between dry matter digestibility and cumulative production of gas and methane (mg/ml) was statistically equivalent (p>0.05) among all treatments. The final volume of gas and methane (Vf) and its rate of production throughout the fermentation process (k), estimated from the Gompertz model, were also higher (p<0.05) for treatments including potato. Increased methane production is the result of higher dry matter digestibility according CNE level increases in the mixture. Under the in vitro model and in contrast to literature reports, the greater inclusion of CNE did not reduce methane production. [ABSTRACT FROM AUTHOR]

This study assessed the effect of protected nitrate on methane emissions, energy utilization, and nitrogen balance in Brangus steers. Nine housed steers were assigned to one of three treatments that differed in a non- protein nitrogen source: urea (control), protected nitrate (NP), and free nitrate (NL). The experiment was performed in three periods by using a 3x3 Latin square design repeated three times. No animal showed signs of nitrate intoxication. NP steers reduced the intake and digestibility of dry matter, protein, and gross energy. Dietary nitrates reduced methane production by 23%. Nitrate levels of 3% in dry matter were safe for steer diets. In conclusion, the nitrate protection method presented here reduced dry matter intake, nitrogen retention, digestibility, and energy utilization efficiency. [ABSTRACT FROM AUTHOR]