(In)efficiency of meat v. vegetables

Google says a cow eats about 25lbs of vegetation per day.

It also says beef cows are slaughtered at 36 months of age.

36 months x 30 days = 1080 days.
25 lbs/day x 1080 days = 27,000 lbs of food.

Google also says you get 440lbs of beef from a cow.

27,000 / 440 = 36 (approximately)

So that means it takes 36 lbs of grass or other vegetation to get one pound of meat out of a cow.

So the "35 times" number in this article approximately matches that:
https://vegnews.com/2019/11/one-serving-of-meat-is-35-times-more-environmentally-damaging-than-a-serving-of-vegetables-oxford-study-finds