As I understand it someone did a count of all the animals killed in the production of a vegan diet and in pure numbers it was more than if you any ate beef by a huge amount. Will try to find the original study…
When you find it look hard at who made this "study", and check if they counted in the same way. For example counting the animals killed during the production of the food used to feed the animals raised for their meat.
That study was so flawed, it's not even funny. It took one specific scenario in Australia, where farmers had to kill a lot of rodents (due to a seasonal plague) to protect their crop and compared that to a single animal slaughtered for a meat dish. They completely failed to mention that livestock are fed that exact same crop, that the farmers were killing the rodents for. IIRC there a couple such "studies", but all similarly flawed.