Introduction of solid feeds in the ration of calves has been shown to increase rumen size and stimulate rumen fermentation. With the initiation of bacterial fermentation in the rumen, the intermediary metabolism moves from a glucose-based to a volatile fatty acid-based metabolism, which releases methane. MootralTM has been identified as a promising plant-derived feed supplement to reduce methane emission in dairy and beef cattle. Therefore, the present study aimed at quantifying and mitigating the methane emissions in calves until the slaughtering age of 28 weeks. The study consisted of 20 Holstein bull calves at a commercial farm, assigned randomly into 2 groups (control n = 10;treatment n = 10), for 2 weeks of adaptation and 8 weeks of sample collection. The calves were fed an increasing amount of milk replacer and ad libitum wheat straw. Mootral was fed once a day to the treatment calves. Methane was measured using GreenFeed units where concentrate feed was offered as bait. The calves were weighed at the start and every four weeks during the experiment. The calves in the treatment group had lower methane emissions (54 g/d) compared to the control group (70 g/d), a reduction of 22.8%. In contrast, carbon dioxide emission and dry matter intake did not differ significantly between the study groups. Moreover, no negative impact on the average daily weight gain and carcass weight was observed in Mootral fed calves. Although the methane emission (g/kg body weight) was lower in treatment than in the control group, the absolute difference between the groups narrowed with increasing age of the calves. The results suggest a need to increase the dose in line with the increased body weight and intake of the calves. In conclusion, Mootral effectively reduced methane in calves. Further trials to determine the optimal dose for calves are warranted, and as well studies to investigate if interventions (such as Mootral) applied at an earlier life cycle stage would have an impact on methane emissions at later stages of cattle’s life, would be of scientific interest.
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