An evaluation of the accuracy and precision of methane prediction equations for beef cattle fed high-forage and high-grain diets

Abstract

The study determined the performance of equations to predict enteric methane (CH 4 ) from beef cattle fed forage-and grain-based diets. Many equations are available to predict CH 4 from beef cattle and the predictions vary substantially among equations. The aims were to (1) construct a database of CH 4 emissions for beef cattle from published literature, and (2) identify the most precise and accurate extant CH 4 prediction models for beef cattle fed diets varying in forage content. The database was comprised of treatment means of CH 4 production from in vivo beef studies published from 2000 to 2015. Criteria to include data in the database were as follows: animal description, intakes, diet composition and CH 4 production. In all, 54 published equations that predict CH 4 production from diet composition were evaluated. Precision and accuracy of the equations were evaluated using the concordance correlation coefficient (r c ), root mean square prediction error (RMSPE), model efficiency and analysis of errors. Equations were ranked using a combined index of the various statistical assessments based on principal component analysis. The final database contained 53 studies and 207 treatment means that were divided into two data sets: diets containing ⩾400 g/kg dry matter (DM) forage (n = 116) and diets containing ⩽200 g/kg DM forage (n = 42). Diets containing between ⩽400 and ⩾200 g/kg DM forage were not included in the analysis because of their limited numbers (n = 6). Outliers, treatment means where feed was fed restrictively and diets with CH 4 mitigation additives were omitted (n = 43). Using the high-forage dataset the best-fit equations were the International Panel on Climate Change Tier 2 method, 3 equations for steers that considered gross energy intake (GEI) and body weight and an equation that considered dry matter intake and starch:neutral detergent fiber with r c ranging from 0.60 to 0.73 and RMSPE from 35.6 to 45.9 g/day. For the high-grain diets, the 5 best-fit equations considered intakes of metabolisable energy, cellulose, hemicellulose and fat, or for steers GEI and body weight, with r c ranging from 0.35 to 0.52 and RMSPE from 47.4 to 62.9 g/day. Ranking of extant CH 4 prediction equations for their accuracy and precision differed with forage content of the diet. When used for cattle fed high-grain diets, extant CH 4 prediction models were generally imprecise and lacked accuracy.

Global beef cattle methane emissions: yield prediction by cluster and meta-analyses

“…Examples of metaanalyses focussed on mitigation strategies include Ungerfeld et al (2007), Beauchemin et al (2008), Eugène et al (2008), Grainger and Beauchemin (2011), Jayanegara et al (2011), Patra (2013, Hristov et al (2013a) and the more recent papers by Veneman et al (2016) and Escobar-Bahamondes et al (2017). Ramin and Huhtanen (2013) estimated beef cattle MY as 21.9 g/kg DMI from their meta-analysis of five beef papers (Kirkpatrick et al 1997;Kurihara et al 1999;McGinn 2005, 2006;Beauchemin et al 2007).…”

“…Escobar- Bahamondes et al (2017) recently evaluated MP prediction equations from five studies (Ellis et al 2007(Ellis et al , 2009Yan et al 2009;Ricci et al 2013;Moraes et al 2014). Only Ricci et al (2013) and Yan et al (2009) are included in MitiGate and they are not beef cattle studies.…”

“…Only Ricci et al (2013) and Yan et al (2009) are included in MitiGate and they are not beef cattle studies. Escobar-Bahamondes et al (2017) noted that the data from Ellis et al (2009) ;Yan et al (2009) and Ricci et al (2013) that they used were not available in the published literature.…”

Estimating enteric methane production for beef cattle using empirical prediction models compared with IPCC Tier 2 methodology

“…Escobar-Bahamondes et al (2017a) showed that many equations lacked accuracy, as they were not specific for high-forage or high-grain diets. According to that study, a set of equations was identified that predicted CH 4 production as well as or better than the IPCC Tier 2 methodology.…”

Universally applicable methane prediction equations for beef cattle fed high- or low-forage diets

“…Empirical models specifically for beef cattle (e.g., Ellis et al 2007Ellis et al , 2009Yan et al 2009;Muir et al 2011;Moraes et al 2014), for beef and dairy cattle (e.g., Ricci et al 2013;Ellis et al 2014), or for beef and dairy cattle and sheep (Ramin and Huhtanen 2013) have been proposed. However, the uncertainty of estimates of eCH 4 from beef cattle using these models can be substantial (Hippenstiel et al 2013;Moraes et al 2014), especially for cattle fed high-grain diets (Escobar-Bahamondes et al 2016). Part of this uncertainty could be due to the limitations of the model, but variability can also be due to the limited number of records, regional representation of data, and statistical distribution or range of each variable within the development database.…”