In the Vedic scriptures there are concessions for meat-eaters. It is said that if one wants to eat meat, he should kill a goat before the goddess Kālī and then eat its meat. Meat-eaters are not allowed to purchase meat or flesh from a market or slaughterhouse. There are no sanctions for maintaining regular slaughterhouses to satisfy the tongues of meat-eaters. As far as cow-killing is concerned, it is completely forbidden. Since the cow is considered a mother, how could the Vedas allow cow-killing? In the Bhagavad-gītā (18.44) there is a clear injunction that cows should be protected: kṛṣi-gorakṣya-vāṇijyaṁ vaiśya-karma svabhāva-jam. “The duty of vaiśyas is to produce agricultural products, trade and give protection to cows.” Therefore it is a false statement that the Vedic scriptures contain injunctions permitting cow-killing.
Ref >> Srila Prabhupada Vani.