India's central Madhya Pradesh state has also ordered setting up nearly 150 shelters for stray cattle.
Chief Minister Uma Bharati of the Hindu nationalist Bharatiya Janata Party had promised during her election campaign she would ban cow slaughter if she won.
Under the new law, cow slaughter in Madhya Pradesh carries jail sentence and a fine.
The cow is sacred to more than 800 million Hindus across India and killing a cow or eating beef is taboo. However, Muslims and Christians eat beef, though it is hard to come by in large parts of the country.
The import of beef is banned under India's import policy. But India does export beef, mainly to Middle Eastern countries.