Worshiping cow is equal to worshiping Krishna
From the life of Krishna we can understand the importance Krishna gave to the cows.
There were two instances where Krishna has tried to convince us of how one can win Krishna by serving a cow.
Mata Yashoda took Krishna to cow and prayed cow for Krishna’s well-being, when she saw Krishna being attacked by the demon Putana. Krishna’s parents knew that protecting cow alone can bring health, wealth and prosperity. Mata Yashoda told us that cow protects us from ill-will and negative energies. That was the first instance where we were guided by Krishna about importance of cows.
The second incidence was when the King of heaven: Indra wanted to kill the people of Vrindavan, when he came t0 know that they have stopped worshipping him. It is regarded as the First sinful act of person blessed with transcendental qualities-“Dev aparadh”.
The merciful Krishna instead of giving any curse or personal punishment to King Indra took the effort of lifting the Goverdhan for seven consecutive days. Despite the fact that Krishna and his men were troubled, Krishna forgives Indra as he donated Surbhi cow to Krishna. This shows us How Krishna was in the awe of cows.
Krishna always taught about importance of cows through his actions. His love for cows is also seen from his two names “Gopala- the protector of the cows and Govinda- “one who brings satisfaction to the cows”
In the 11th (11.11.43) Canto of Shrimad Bhagwatam Krishna told his beloved cousin Udhava that he can be worshiped by offering cow grass and other suitable grains.