Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 35
व्रजस्य राम: प्रेमर्धेर्वीक्ष्यौत्कण्ठ्यमनुक्षणम् ।मुक्तस्तनेष्वपत्येष्वप्यहेतुविदचिन्तयत् ॥ ३५ ॥
vrajasya rāmaḥ premardhervīkṣyautkaṇṭhyam anukṣaṇammukta-staneṣv apatyeṣv apyahetu-vid acintayat
Because of an increase of affection, the cows had constant attachment even to those calves that were grown up and had stopped sucking milk from their mothers. When Baladeva saw this attachment, He was unable to understand the reason for it, and thus He began to consider as follows.
The cows had younger calves who had started sucking milk from their mothers, and some of the cows had newly given birth, but now, because of love, the cows enthusiastically showed their affection for the older calves, which had left off milking. These calves were grown up, but still the mothers wanted to feed them. Therefore Balarāma was a little surprised, and He wanted to inquire from Kṛṣṇa about the reason for their behavior. The mothers were actually more anxious to feed the older calves, although the new calves were present, because the older calves were expansions of Kṛṣṇa. These surprising events were taking place by the manipulation of yoga-māyā. There are two māyās working under the direction of Kṛṣṇa — mahā-māyā, the energy of the material world, and yoga-māyā, the energy of the spiritual world. These uncommon events were taking place because of the influence of yoga-māyā. From the very day on which Brahmā stole the calves and boys, yoga-māyā acted in such a way that the residents of Vṛndāvana, including even Lord Balarāma, could not understand how yoga-māyā was working and causing such uncommon things to happen. But as yoga-māyā gradually acted, Balarāma in particular was able to understand what was happening, and therefore He inquired from Kṛṣṇa.