UC Davis

The emergence of beef on dairy crossbreeding has increased in recent years, shifting the ratio of dairy-influenced cattle within the beef supply chain toward crossbreds. There is a significant knowledge gap regarding the impact of breed composition and the calf-fed versus yearling systems on methane emissions. The present study compared performance and enteric methane (CH4) and hydrogen (H2) emissions in calf-fed Holstein, calf-fed Holstein Angus crosses, and yearling-fed Angus steers during the finishing period. Eight Black Angus steers (ANG; initial body weight (BW) = 404 ± 13kg), 8 Black Angus x Holstein crossbred steers (CRS; initial BW = 384 ± 13kg), and 8 Holstein steers (HOL; initial BW = 375 ± 13kg) were used in a randomized, incomplete block design for a 175-day feeding trial. Initial BW data (day –14) was used to block cattle into 3 pens (8 head per pen), with breed as the treatment and distributed across heavy, medium, and light blocks. All steers were fed the same feedlot finisher ration and individual dry matter intake (DMI) was monitored daily using Roughage Intake Control Systems (RICS; Hokofarm Group, Emmeloord, The Netherlands). Cattle were individually sampled biweekly for enteric CH4 and H2 emissions using a GreenFeed machine (C-Lock, Inc., Rapid City, SD). During each biweekly sampling, a three-day sampling window was set where cattle were brought to a GreenFeed pen every 6 hours to achieve a full, 24h emission measurement from each steer. When brought to the GreenFeed pen, each individual was allowed approximately a 6-minute sampling at the GreenFeed. Individual BW was collected biweekly. Individual hot carcass weight (HCW), ribeye area (REA), yield grade (YG), quality grade (QG), and liver abscess scores were collected at harvest. All data were analyzed using R Software. Initial BW was similar across cattle in the three treatment groups, but final BW in ANG vs CRS and HOL steers was greater (P < 0.01). ANG vs CRS and HOL steers had 12% and 11% higher DMI (P < 0.05), respectively. Steers across the three treatment groups were similar for CH4 production (g/head/day), CH4 yield (g/kg DMI), CH4 intensity (g/kg BW), and H2 production. ANG vs CRS and HOL steers had 31% and 32% lower H2 yield (P < 0.01) respectively, and 44% lower H2 intensity (P < 0.05). With understanding beef on dairy cross enteric emissions through this research, there is now further investigation needed to quantify lifetime GHG emissions between beef on dairy crossbreds and traditional beef systems. These results will inform environmental and social sustainability, alongside the quality effects of integrating beef on dairy cross cattle into the beef supply chain.