What a loaded question.

Outside of the fact that a single cows life provides about 900 meals for humans, and the scraps left over make boots that last for a decade and also feed our cats and dogs. Plus, it’s delicious.

Yeah so, the amount of meals is correct. But that’s about it. I mean, I can’t say about the taste, to each their own, but one kg of cow meat needs two dozen kg of grain.

That’s about as inefficient as it gets.

As for the leather, the industry doesn’t like products that last a decade, so it isn’t actually using the leather in such a way. Industrial leather boots last a year tops.

Finally, pet food is made out of discarded cuts of meat, the uglies, etc. But also lots of cereals, and vegetables.

So we could really afford eating less meat. It isn’t good for anything. Not for us, not for the other species (certainly not for the cows, that get often half assed butchered in a hasty way because of quotas and profit), and absolutely not for the ecosystem.

But I guess the taste is all that matters.

Cows are not all fed on grain. A lot of cows are ranched on land that would not be suitable for growing grain crops.

Whatever their food is, they need 1kg of beef requires 24kg of grain's worth of energy.

But as I pointed out, many cattle are ranched on land that cannot grow grain. They can't grow the sorts of crops that humans eat, only the sorts of crops that cattle eat. If cattle weren't being ranched on those lands they wouldn't be producing edible grain instead, or any other food that humans could eat. So the inefficiency is moot when it comes to the amount of nutrition produced, removing the cattle from that land would simply reduce the total amount of food we have available.

Sure, if you remove the cattle then wild animals could come in to replace them, but we should make sure that's not going to result in starvation and poverty if we do that. Many areas of the world have subsistence ranching by the locals.

Interesting. However, a search says that feeding all the grass (or whatever) to cattle takes that food away from existing ecosystems in dry areas and potentially allow exotic weeds to take over land. So we probably don't want this to expand to the point where we intrude on dry ecosystems.