We need meat to grow muscle!
...Straight after a meal, the rate of synthesis doubles, prompted by the arrival of a large amount of amino acids.
The rate of the breakdown of protein is highest in-between meals.
The difference between the two rates determines how much protein remains in the muscle.
But, in older animals - and, it is believed humans - the amino acid stimulus prompting synthesis is less effective, and the process slows down.
However, the breakdown of proteins is not, leaving older animals with less protein than their younger counterparts.
The researchers compared protein breakdown in young (eight-month-old) and old (22-month) rats.
They discovered that the slow down in degradation that normally follows a meal does not occur in old animals, so there is excessive breakdown.
But when the scientists boosted levels of one amino acid, leucine, the balance of synthesis and breakdown was restored. ...
BBC, full article
However, there is no medical, economical or any other necessiity to keep animals in the miserable conditions they are presently being kept. This alone would justify vegetarians and vegans
if they needed to be justified, which they clearly don't!