Methane emissions by livestock are responsible for 14.5% of the global emissions. The number can be actually higher considering that methane is 84 times more potent than CO2 in a 20-year span. Considering the net-zero targets for mid-century, 84x potency may be more relevant than 25x used to get the 14.5% figure. Although going vegan can help, there is slim chance that veganism can spread in such speed and scale that will put a big dent in time.
In that spirit, is there any cost analysis of how much changing diet of cows, or adding supplements to their food, can affect the methane they emit? One could also do selective breeding with the goal of reducing their methane emissions, but that would be slower than changing diet.