The US culls 350 million male chicks per year, per this article. Wikipedia says billions of male chicks are culled worldwide, which seems plausible when accounting for EU, China, India, SA, SEA etc. The citation on Wikipedia looks legit to me as well.

Edit: Wikipedia does indeed cite several different figures, including a "billions" number which does not seem plausible. Thanks monster_truck for pointing this out, and apologies for my misunderstanding!