nonsense, cattle only make up 1% of all manmade greenhouse gas emissions.
You can get quite philosophical with that statement. Are cow burps "man-made"?
On the other hand, the UN estimates that the whole livestock commodity chain contributes 18 % of all green house gas emissions, which is more than transport. This is an orange to your 1% apple, and the numbers should not be compared. It does however tell us what would happen to green house gas emissions if we stopped (or seriously cut down on) keeping livestock (primarily for meat, dairy, eggs and wool).
Also, you might want to consider that there is more cattle than humans on this planet, and most cows don't eat just grass. They are fed corn, soy, grains, and antibiotics.