Śatapatha Brāhmaṇa ("of a hundred paths") 2.5.1.6

2.5.1.6

tadvai paya evānnam | etaddhyagre prajāpatirannamajanayata tadvā annameva prajā annāddhi sambhavantīdaṃ hi yāsāṃ payobhavati stanāvevābhipadya tāstataḥ sambhavantyatha yāsām payo na bhavati jātameva tā athādayanti tadu tā annādeva sambhavanti tasmādvannameva prajāḥ

Now that milk is indeed food; for in the beginning Pragâpati produced it for food. But that food also means living beings (progeny), since it is by food that they exist: by resorting to the breasts of those who have milk, they continue to exist. And those who have no milk are nursed by the former as soon as they are born; and thus they exist by means of food, and hence food means progeny.