DO COW FARTS REALLY SIGNIFICANTLY CONTRIBUTE TO GLOBAL WARMING?

The text says that there are some scientists and experts that have studied how cow farts contribute to global warming. There are lots of cows in the world (about 1.3 to 1.5 billion) and their farts expel a big amount of methane gas, so that's a problem. Methane gas is very harmful for the environment, and it contributes to wipe out the ozone layer.
For this problem, scientists and experts have proposed some solutions:
One of the solutions is putting garlick in cows' food, because it helps them to expel less methane gas.
Another solution is adding plants with high levels in tannis to their diet.
Finally, some farms have experimented putting their cows into a plastic bubble, which takes the expelled gas and turns it into electricity.
I reckon that it's cruel and inhuman. Animals shouldn't live inside artificial bubbles.
So what's the conclusion of the text?
I really think that cow farts really contribute to Global Warming, although we have just seen that there are several solutions to reduce methane gas. If cows change their diet, they will expel less methane gas.