Until the end of this turn, all face-up Beast-Type monsters on your side of the field gain 200 ATK for each Beast-Type monster on your side of the field.
Rulings
Individual Card FAQs
โThe Big March of Animalsโ applies its effect at resolution of the card and does not recalculate during the turn. Its effect lasts as long as the affected monsters remain face-up on the field, or until the End Phase.
โThe Big March of Animalsโ does not affect monsters Summoned after it resolves.
โThe Big March of Animalsโ does not count or affect face-down monsters.
This is not an effect that targets. It is applied to all face-up Beast-Type monsters on your side of the field.