"The conchshell and cow dung are bone and stool of two living beings. But because they have been recommended by the Vedas as pure, people accept them as such because of the authority of the Vedas."
(Srimad Bhagavatam-----introduction).

The examples given by the Lord of the conchshell and the cow dung are very much appropriate in this connection. If one argues that since cow dung is pure, the stool of a learned brāhmaṇa is still more pure, his argument will not be accepted. Cow dung is accepted, and the stool of a highly posted brāhmaṇa is rejected.
(Srimad Bhagavatam-----introduction).

From this we can certainly assume that Lord Ṛṣabhadeva was transcendentally blissful. His stool and urine were so completely different from material stool and urine that they were aromatic. Even in the material world, cow dung is accepted as purified and antiseptic. A person can keep stacks of cow dung in one place, and it will not create a bad odor to disturb anyone. We can take it for granted that in the spiritual world, stool and urine are also pleasantly scented. Indeed, the entire atmosphere became very pleasant due to Lord Ṛṣabhadeva's stool and urine.
(Srimad Bhagavatam-----5:5:33-----purport).

Pañca-gavya, the five products received from the cow, namely milk, yogurt, ghee, cow dung and cow urine, are required in all ritualistic ceremonies performed according to the Vedic directions. Cow urine and cow dung are uncontaminated, and since even the urine and dung of a cow are important, we can just imagine how important this animal is for human civilization. Therefore the Supreme Personality of Godhead, Kṛṣṇa, directly advocates go-rakṣya, the protection of cows.
(Srimad Bhagavatam-----8:8:11-----purport).

When bathing the Deity in the abhiṣeka ceremony with various liquids, such as milk, honey, yogurt, ghee, cow dung and cow urine, it is customary to supply yellow garments. In this way the abhiṣeka ceremony for the goddess of fortune was performed according to the regular Vedic principles.
(Srimad Bhagavatam-----8:8:15-----purport).

All Vedic knowledge is infallible, and Hindus accept Vedic knowledge to be complete and infallible. For example,cow dung is the stool of an animal, and according to smṛti, or Vedic injunction, if one touches the stool of an animal he has to take a bath to purify himself. But in the Vedic scriptures cow dung is considered to be a purifying agent. One might consider this to be contradictory, but it is accepted because it is Vedic injunction, and indeed by accepting this, one will not commit a mistake; subsequently it has been proved by modern science that cow dung contains all antiseptic properties. So Vedic knowledge is complete because it is above all doubts and mistakes, and Bhagavad-gītā is the essence of all Vedic knowledge.
(Bhagavad-Gita-----introduction).

Even now in the Indian villages surrounding Vṛndāvana, the villagers live happily simply by giving protection to the cow. They keep cow dung very carefully and dry it to use as fuel. They keep a sufficient stock of grains, and because of giving protection to the cows, they have sufficient milk and milk products to solve all economic problems. Simply by giving protection to the cow, the villagers live so peacefully. Even the urine and stool of cows have medicinal value.
(Srimad Bhagavatam-----10:6:19-----purport).

Even in the houses of the cultivators, who were not very advanced in the modern ways of civilization, the ladies used to know how to chant mantras to give protection to children with the help of cow dung and cow urine. This was a simple and practical way to give the greatest protection from the greatest dangers. People should know how to do this, for this is a part of Vedic civilization.
(Srimad Bhagavatam-----10:6:22-23-----purport).

The ingredients of pañca-gavya are milk, yogurt, ghee (clarified butter), cow urine and cow dung. All these items come from the cow; therefore we can just imagine how important the cow is, since its urine and stool are required for bathing the Deity. The pañcāmṛta consists of five kinds of nectar—yogurt, milk, ghee, honey and sugar. The major portion of this preparation also comes from the cow. To make it more palatable, sugar and honey are added.
(Sri Caitanya Caritamrta-----2:4:61-----purport).

Nails and hair are undoubtedly inanimate, but they come not from the animate living being but from the inanimate material body. Similarly, the argument that the scorpion comes from cow dung, meaning that a living entity comes from matter, is also unsound. The scorpion which comes out of the cow dung is certainly a living entity, but the living entity does not come out of the cow dung. Only the living entity's material body, or the body of the scorpion, comes out of the cow dung. The sparks of the living entities, as we understand from the Bhagavad-gītā, are injected into material nature, and then they come out.
(Krsna Book).

According to Vedic principles, bones and dung are generally considered very impure. If one touches a bone or stool, he must take a bath immediately. That is the Vedic injunction. Yet the Vedas also enjoin that a conchshell, although the bone of an animal, and cow dung, although the stool of an animal, are very much sanctified. Even though such statements appear contradictory, on the basis of the Vedic version we still accept the fact that conchshells and cow dung are pure and sanctified.
(Sri Caitanya Caritamrta-----2:6:136-----purport).