Grass that may help tackle global warming by cutting the level of methane given off by cows is being developed [...] However, some scientists suggest that a cow’s absolute methane emissions might go up. Alistair Macrae, a lecturer in farm animal health and production at the University of Edinburgh, UK, says a diet too rich in highly digestible carbs can actually increase the amount of methane a cow belches out. [...] Beever agrees and says, ’It could increase methane emissions but it could also increase milk yields, effectively cutting the amount of methane produce per litre of milk.’