Śukadeva Gosvāmī said: When Lord Rāma and Lord Kṛṣṇa attained the age of paugaṇḍa (six to ten) while living in Vṛndāvana, the cowherd men allowed Them to take up the task of tending the cows. Engaging thus in the company of Their friends, the two boys rendered the land of Vṛndāvana most auspicious by imprinting upon it the marks of Their lotus feet.
Lord Kṛṣṇa wanted to encourage His cowherd boyfriends, who had been swallowed by Aghāsura and then stolen by Lord Brahmā. Therefore the Lord decided to bring them into the palm-tree forest called Tālavana, where there were many delicious ripe fruits. Since Lord Kṛṣṇa's spiritual body had apparently grown slightly in age and strength, the senior men of Vṛndāvana, headed by Nanda Mahārāja, decided to promote Kṛṣṇa from the task of herding calves to the status of a regular cowherd boy. He would now take care of the full-grown cows, bulls and oxen. Out of great affection, Nanda Mahārāja had previously considered Kṛṣṇa too small and immature to take care of full-grown cows and bulls. It is stated in the Kārttika-māhātmya section of the Padma Purāṇa:

śuklāṣṭamī kārttike tu
smṛtā gopāṣṭamī budhaiḥ
tad-dinād vāsudevo 'bhūd
gopaḥ pūrvaṁ tu vatsapaḥ
"The eighth lunar day of the bright fortnight of the month of Kārttika is known by authorities as Gopāṣṭamī. From that day, Lord Vāsudeva served as a cowherd, whereas previously He had tended the calves."

The word padaiḥ indicates that Lord Kṛṣṇa blessed the earth by walking on her surface with His lotus feet. The Lord wore no shoes or other footgear but walked barefoot in the forest, giving great anxiety to the girls of Vṛndāvana, who feared that His soft lotus feet would be injured.
(Srimad Bhagavatam-------10:15:1-------translation and purport).

Another place nearby is named Hāṅṭugāḍā. It is said that Lord Nityānanda Prabhu brought all the holy places there. Therefore the people in the surrounding villages go there instead of to the Ganges to take bath. It is named Hāṅṭugāḍā because Śrīla Nityānanda Prabhu used to perform the dadhi-ciḍā festival of distributing chipped rice with yogurt prasādam there and He took the prasādam kneeling down. A sanctified lake in this place is always full of water throughout the year. A great fair is held there during Goṣṭhāṣṭamī, and there is another big fair on the birthday of Śrī Nityānanda Prabhu.
(Sri Caitanya Caritamrta------1:13:61------purport).

Kāliya was residing within the water of the Yamunā, and as a result the back portion of that river had become poisoned. Thus so many cows who had drunk the water had died. Therefore Kṛṣṇa, even though He was only four or five years old, dipped Himself into the water, punished Kāliya very severely and then asked him to leave the place and go elsewhere.
Kṛṣṇa said at that time that the cows are worshiped even by the demigods, and He practically demonstrated how to protect the cows. At least people who are in Kṛṣṇa consciousness should follow in His footsteps and give all protection to the cows. Cows are worshiped not only by the demigods. Kṛṣṇa Himself worshiped the cows on several occasions, especially on the days of Gopāṣṭamī and Govardhana-pūjā.
(Nectar of Devotion).