Effects of brown seaweed supplementation on methane and carbon dioxide emissions and productivity indicators in pregnant replacement heifers

Introduction Beef cattle naturally emit methane during the feed digestion process, which significantly contributes to agriculture’s greenhouse gas footprint. As a short-term strategy, feed supplements are considered an effective approach to mitigate methane emissions and improve feed efficiency. Methods This study therefore assessed the impact of four levels (0.0%, 0.5%, 1.0%, and 2.0% DM basis) of North Atlantic Organics (Atlantic GRO®) brown seaweeds on growth and feed efficiency in pregnant beef heifers over a 50-day trial, as well as gas emissions using a hood chamber system for two 24-h chamber periods. Results Results showed that seaweed supplementation did not adversely impact ( p > 0.51) growth performance with any level of supplementation. However, methane emissions were 8.2% and 8.7% lower in the 1.0% and 2.0% groups, respectively, than in the control group ( p < 0.05). Also, significantly ( p < 0.05) lower CO 2 emissions and O 2 consumption were observed in heifers fed diets with the 1.0% and 2.0% inclusion levels of brown seaweeds compared to the control. Discussion These findings suggest that 1.0% and 2.0% dietary supplementation with North Atlantic GRO® seaweed may reduce methane and carbon dioxide emissions without adverse effects on growth performance of pregnant beef heifers.