A Vedic sacrifice is not an ordinary performance. The demigods used to participate in such sacrifices, and the animals sacrificed in such performances were reincarnated with new life. In this age of Kali there are no powerful brahmanas who can invite the demigods or give renewed life to animals. Formerly, the brahmanas well conversant in Vedic mantras could show the potency of the mantras, but in this age, because there are no such brahmanas, all such sacrifices are forbidden. The sacrifice in which horses were offered was called asvamedha. Sometimes cows were sacrificed (gavalambha), not for eating purposes, but to give them new life in order to show the potency of the mantra. In this age, therefore, the only practical yajna is sankirtana-yajna, or chanting of the Hare Krsna mantra twenty-four hours a day.