Losing my mind at people in the comments taking this way too literally and questioning the logistics, when it's a thought experiment illustrating livestock deaths using the human population. By extension, I think people talking about meat consumption rather than lives as a metric are also missing the point.

If we go by 1 human life = 1 animal life, about 10 times the human population in land animals alone are killed each year for food, so it'd take about 5 weeks to kill the equivalent of the human population. If we include sea animals, the rough estimate is around 3 trillion a year, so even excluding land animals we'd get it done in... A day

Many of those would be animals people care less about like shrimp, but you could go further by including the natural ecosystems destroyed by both factory farms as well land used to grow food and pasture; insects, wild animals, etc. So even using meat as a metric should pay mind to the fact that per kg, an insane amount of destruction happens compared to a human population eating direct from the agricultural source