Yes, in Jain Dharma a pachkhan should be taken for a specific vow, in a specific form, and with proper understanding. It is not something to take casually “about anything.”

A pachkhan is usually taken for things like:

• fasting or partial fasting
• limiting food, water, or certain foods
• avoiding certain actions for a fixed time
• observing restraint and repentance

Important points:

• It should be clear and definite.
• It should be within your capacity.
• It should not be taken lightly or broken carelessly.
• If possible, take it under guidance of a Guru Bhagwant or according to proper Jain tradition.

If you meant something else by “cow,” I can still answer in Jain terms, but as written, the correct principle is: pachkhan is for a defined vow, not for vague or random things.