Those are plant suckers a natural plant response once the ear was removed.
But the ears have not been removed yet. More than 50% plants showing suckers and tillers.
I was wondering if it could reduce the total yield.
Yes, yield on single ears will be reduced however you will have more ears. Plant spacing will have the most influence on the plants ability to sucker. Consider planting the corn with no further than 8 inches in between seeds in the row.