I remember an elder telling me in all seriousness that during WWII, lions and other carnivores in London zoos were fed straw because of a meat shortage, and that the cats' health was better than when they ate meat.
I don't know about the big cats in the London zoo being healthier during WWII or not but the part about the vegetarian diet is semi-true.
But with most things JW, the, "Devil is in the details" as they say and all the important details are left out here. JW's seem to think this means the big cats were eating alfalfa pellets like rabbits LOL.
The reality is there are no wild forms of vegatation on this planet that in any way approximate what these big cats were fed and there are several reasons for this:
Probably the single biggest problem involved with a large, robust animal subsisting on a vegetarian diet is protein. Plant material generally is not high in protein. This doesn't mean that it's impossibe for a big, strong animal to be a vegetarian, (Like the elephant or Cape buffalo for example....) it's just that it must have an efficient mechanism for assimilating protein from the vegetation that it consumes. First and foremost, in order to gain access to the proteins within the cell, a vegetarian must rupture the cell walls of plant material.
With animals that are designed to be vegetarians, this occurs in a two stage process: 1: Mechanical breakdown (i.e. Grinding with the teeth) 2. Chemical breakdown (i.e. Biological breakdown in multi-chambered stomachs or enlarged hindguts.) A big cat is capable of neither. It lacks both the high-crowned grinding teeth to start the process as well as the specialized digestive organs to finish it.
Another problem with big cats is taurine. Taurine is an essential amino acid that is not found in vegetation. Animal that are designed to be vegetarians can syntheize taurine from other amino acids but no member of the cat family can do this. When a cat is fed a vegetarian diet, it must be fortified with taurine from a non-vegetarian source (e.g. Meat or bone meal) or the cat will die.
In a zoo, these problems are easily overcome because this is not a problem for Man. After all, humans have been grinding wheat to make flour for thousands of years and any commercial dry pet food is a mixture of a variety of constituents that has been thoroughly ground, processed and fortified. In the wild, though this would be entirely impossible.