Whilst I appreciate the humour in discussing cows farting, the truth is that the methane emissions are largely emitted via belching. The methane emissions are, what is to a large part, responsible for the greenhouse gas effect.
Cows and other ruminants produce high value human edible feed from resource not otherwise available for human consumption. Put simply, humans can’t live on straw and grass, but milk and cheese are high value foods that maximise food security and can make an important contribution to a healthy human diet.
Methane emissions are indeed highly topical. A wide range of approaches to decrease methane emissions have been tested but in many cases these approaches are not long term. Whilst a short term decrease in methane might occur these effects are not prolonged. Finally, the issue of public perception needs to consider a range of approaches based on the addition of antibiotics or non-naturally occurring chemicals have been evaluated but it is difficult to see them being widely accepted by society. The possibility that plant extracts could have a long term effect on emissions and no adverse effect on product quality is highly appealing.