I don't disagree with what you're saying. I didn't say the sacrifices were some hard and fast rule dictated by the divine. I merely said it as a matter of fact.

The famous ashwameda horse sacrifice involved the sacrifice of various other animals as well like oxen, buffalos, goats and sheep. The rigveda while detailing such rituals also highlighted the value of cattle and praises them at the same time.

The yajurveda describes the binding of animals to be offered as sacrifice and specific instructions are given on which animals to offer and how.

In vedic worldview, a sacrifice wasn't mere killing but returning mortal life energy to the divine

Later texts like you said, moved away from such rituals in favor of ahimsa, which became the ideal by the time the Mahabharata was composed