Less intelligent people underestimate the value of cow’s milk. Cow’s milk is also called gorasa, or the juice from the body of the cow. Milk is the most valuable form of gorasa, and from milk we can prepare many important and valuable foodstuffs for the upkeep of the human body. The killing of cows by human society is one of the grossest suicidal policies, and those who are anxious to cultivate the human spirit must turn their attention first toward the question of cow protection.

From: Light of the Bhagavata, 27, by Srila Prabhupada