Everyone has to eat somebody, and nature’s law is one living being is eating another living being. Jīvo jīvasya jīvanam. The snake is eating the frog, the frog is eating another small animal or some flies, and the snake is eaten by the mongoose, and the mongoose eaten by somebody else, by cat or by dog. So this is the law of nature. Therefore the human being is suggested that “Eating is required, but you don’t have to eat like the lower animals. You take Kṛṣṇa prasādam. In the Bhagavad-gītā it is said, patraṁ puṣpaṁ phalaṁ toyaṁyo me bhaktyā prayacchati: [Bg. 9.26] “Anyone who is offering Me with devotion and love leaves, vegetables, fruits, flowers, milk, that I take.” So we take Kṛṣṇa prasādam, the remnants of foodstuff left by Kṛṣṇa or God. So that is our philosophy—we take Kṛṣṇa prasādam. Although there is eating from plants that is not killing. Because if we take this flower or fruit from the tree, the tree is not killed. All these food grain plants, when the food grains are ripened, they dry. So it is not required to kill the plant. When it is already dead, you can take the food grains. When you take milk, the cow is not killed. The milk is nothing but transformation of the blood. So we are taking milk means blood. The blood is in a red color, and milk is in white color, but it is blood. Unless it is blood, how so much liquid comes from the body? So we take the same blood in a very intelligible way so that cow may live, he can continue to give me more and more, and I take more benefit from the wonderful food, milk. This is intelligence. And because cow blood is very beneficial for health, if I kill the cow, that is not very good intelligence. In our New Vrindavan, the cows are giving more milk than others because they know we shall not kill them. They are happy.
Ref >> Srila Prabhupada Vani.