312 Emissions Intensity of Growing Cattle with Contrasting Residual Methane Production, Average Daily Gain, Feed Conversion Ratio, Residual Feed Intake, and Feed Intake

Abstract

Abstract Various options exist to produce beef from growing cattle with low environmental footprint normally linked to the genetic merit of animals for traits such as residual feed intake (RFI), residual methane production (RMP), residual CO2e production (RCeP), average daily gain (ADG), feed conversion ratio (FCR), and dry matter intake (DMI; % of BW). The ultimate environmental footprint can be measured through the intensity of methane emissions (IME) in g CH4/kg ADG or the intensity of CO2e (ICDE) adding up both CH4 and CO2 production in g CO2e/kg ADG. The objective of the present study was to compare the IME and ICDE of animals with low, medium, and high traits for RMP, RCDE, ADG, FCR, RFI, and DMI. Five cohorts of 77 steers composite steers and heifers (Angus, Charolais, and Shorthorn) were tested for RFI for 70 d using electronic feeders and CH4 and CO2 production measured using two GreenFeed units in the pens. Only animals with more than 25 visits longer than 3 min were used for the analysis and the final dataset contained 202 animals. Animals within each RFI test were divided into equal groups with low, medium, and high values for each variable RFI, RMP, ADG, FCR, and DMI. Data were averaged for each animal and trial, and analyzed using ANOVA with the fixed effects of group, trial, and their interaction. The IME were different for animals with contrasting RMP, ADG, and FCR (P < 0.05) but not between animals with contrasting DMI and RFI (P > 0.05). The largest difference on IME was found between animals with low and high RMP, ADG, and FCR, and least for RFI and DMI with values being 33.9, 28.1, 22.3, 6.2, and 1.5 g CH4/kg ADG, respectively (Table 1). Results were similar when emissions intensity were expressed as ICDE (Table 1), except animals with low RFI produced less ICDE compared with those with high FI (P = 0.02). Results indicate that the environmental footprint of growing cattle can be reduced with animals with low RMP and high ADG at similar extents, whereas RFI and DMI have lesser impact.