Albert Barnes Commentary Leviticus 22:27

"When a bullock, or a sheep, or a goat, is brought forth, then it shall be seven days under the dam; and from the eighth day and thenceforth it shall be accepted for the oblation of an offering made by fire unto Jehovah." — Leviticus 22:27 (ASV)

No victim was to be offered in sacrifice until it was a week old. The meaning of this law appears to be that the animal should attain a distinct existence by becoming less dependent on its mother and able to provide for its own needs.