Why was Beltine associated with fire and cattle protection?

In Celtic religion, Beltane (or Beltine) marked the beginning of summer and the start of the open pasturing season. The festival was deeply associated with fire and the protection of cattle due to the belief that this time of year was a critical juncture when the boundaries between the human and supernatural worlds were erased.12

During this period, it was believed that witches, fairies, and other supernatural forces roamed freely, posing a threat of enchantment or harm to livestock. To safeguard the animals before they were moved to summer pastures, they were driven between two large bonfires. This ritual was performed as a magical means of purification and protection against disease and evil influences.12345

The festival is often linked to the ancient deity Belenus, who was associated with pastoralism, and the name Beltane itself is traditionally derived from the Old Irish word for "fire" (tene) and the name of a god, possibly Bel or Belenus.154