Development of methane conversion factor models for Zebu beef cattle fed low‐quality crop residues and by‐products in tropical regions

Abstract

The enteric methane conversion factor (Y m) is an important country‐specific value for the provision of precise enteric methane emissions inventory reports. The objectives of this meta‐analysis were to develop and evaluate the empirical Y m models for the national level and the farm level for tropical developing countries according to the IPCC's categorization. We used datasets derived from 18 in vivo feeding experiments from 1999 to 2015 of Zebu beef cattle breeds fed low‐quality crop residues and by‐products. We found that the observed Y m value was 8.2% gross energy (GE) intake (~120 g methane emission head−1 day−1) and ranged from 4.8% to 13.7% GE intake. The IPCC default model (tier 2, Y m = 6.5% ± 1.0% GE intake) underestimated the Y m values by up to 26.1% compared with its refinement of 8.4% ± 0.4% GE intake for the national‐level estimate. Both the IPCC default model and the refined model performed worse in predicting Y m trends at the farm level (root mean square prediction error [MSPE] = 15.1%–23.1%, concordance correlation coefficient [CCC] = 0.16–0.18, R 2 = .32). Seven of the extant Y m models based on a linear regression approach also showed inaccurately estimated Y m values (root MSPE = 16.2%–36.0%, CCC = 0.02–0.27, R 2 < .37). However, one of the developed models, which related to the complexity of the energy use efficiencies of the diet consumed to Y m, showed adequate accuracy at the farm level (root MSPE = 9.1%, CCC = 0.75, R 2 = .67). Our results thus suggest a new Y m model and future challenges for estimating Zebu beef cattle production in tropical developing countries.

Effects of tannins and saponins contained in foliage of Gliricidia sepium and pods of Enterolobium cyclocarpum on fermentation, methane emissions and rumen microbial population in crossbred heifers

“…15% of gross energy (Johnson et al, 2007;Patra and Lalhriatpuii, 2016). In the present study, energy loss as CH4 (% GE) ranged between 8.8 and 9.6%; these values are comparable to those reported for beef cattle fed low-quality rations in tropical regions (Ym between 7-9%; Kaewpila andSommart, 2016, Molina et al, 2016).…”

Effects of long-term diet supplementation with Gliricidia sepium foliage mixed with Enterolobium cyclocarpum pods on enteric methane, apparent digestibility, and rumen microbial population in crossbred heifers

“…The loss of dietary gross energy as CH 4 with the control diet was higher than for the diet with alternate supplementation (8.1 vs 7.6% GE). These values are within the range reported by authors such as Kennedy and Charmley, (2012), Richmond et al (2015), Kaewpila and Sommart, (2016) and Molina et al (2016) for cattle fed improved or native corrected by weight gain was reduced when animals were fed E. cyclocarpum mixed with G. sepium. These findings are consistent with those of Warner et al (2017) who stated that reducing the nutritional quality increased CH 4 emission intensity (g CH 4 /kg of fat-and protein-corrected milk) by 28%.…”

Severe below-maintenance feed intake increases methane yield from enteric fermentation in cattle

“…However, another trial feeding tropical forages under ad libitum conditions reported a greater range of Y m of 5•0-7•2 % (35) , with the highest values occurring when cattle were fed very low-quality grass, at what would have been effectively sub-maintenance requirements. Kaewpila & Sommart (36) calculated (from earlier studies) a Y m of 8•2 % for B. indicus cattle fed low-quality foragebut a limitation of this study is that it does not seek to separate the possible influences of feeding levels from feed quality. While each of the studies detailed above, as well as the one reported here, has been conducted using cattle of predominantly B. indicus origins, it could be tempting to attribute the higher Y m values to breed effects.…”