There are only five well-documented fatal lightning strikes on giraffes between 1996 and 2010. But due to the population of the species being just 140,000 during this time, it makes for about 0.003 lightning deaths per thousand giraffes each year. This is 30 times the equivalent fatality rate for humans.
Pic by Luca Galuzzi
Is it possible that you're thinking of slaughterhouse biomass? I was talking about the biomass of concurrently alive animals and I would expect just milk cows to outweigh chickens in a lot of countries.
My guesstimations are for Flanders, the northern half of Belgium. There's also a lot of chickens, but pigs + cattle weigh more per animal + live longer, which is why I expect them to weigh significantly more than the chickens at any given time. It's not sustainable in any way, I read once that about 90% of the livestock food is imported, 2/3rd of that from outside Europe.
Ah yeah, I was including slaughterhouse biomass
That explains it, thanks!