Mbh 12.268.4a

"'"Syumarasmi said, 'One should perform sacrifice from desire of heaven,--this Sruti is constantly heard by us. Thinking first of the fruit (that is to be attained), one makes preparations for sacrifice. Goat, horse, cow, all species of birds, domestic or wild, and herbs and plants, are food of (other) living creatures. This is heard by us.[1229] Food again has been directed to be taken day after day morning and evening. Then again the Sruti declares that animals and grain are the limbs of Sacrifice.[1230] The Lord of the universe created them along with Sacrifice. The puissant Lord of all creatures caused the deities to perform sacrifices with their aid. Altogether seven (domestic) and seven (wild) animals are indicated as fit for sacrifice. Instead of all being equally fit, each succeeding one is inferior to each preceding one. The Vedas again declare that the whole universe is appointed for sacrifice. Him also that is called Purusha the Vedas have appointed for the same purpose.[1231] This again hath been sanctioned by men of remote and remoter times. What man of learning is there that does not select, according to his own ability, individuals from among living creatures for sacrifice?[1232] The inferior animals, human beings, trees, and herbs, all wish for the attainment of heaven. There is no means, however, except sacrifice, by which they can obtain the fruition of that desire. The deciduous herbs, animals, trees, creepers, clarified butter, milk, curds, meat and other approved things (that are poured on the sacrificial fire), land, the points of the compass, faith, and time which brings up the tale of twelve, the Richs, the Yajuses, the Samans, and the sacrificer himself bringing up the tale to sixteen, and Fire which should be known as the householder,--these seventeen are said to be the limbs of sacrifice. Sacrifice, the Sruti declares, is the root of the world and its course.