I admit I have not read the article yet but I have done independent research into these stats previously a few weeks ago. I found the 30m quoted number is the monthly cull amount. I have seen many references to the 115m or similar numbers but have no idea over what time period. I had my own ~120m number come up from my calculations: The industry claims it takes 4-6 months to clean, disinfect, hatch and re-grow, and get the chickens to egg-laying age. If you take the ~30m and ~4-6m period, you end up around ~120-180m "missing" egg-laying chickens in the flock at any time assuming this replacement is taking place at expected levels.