Navjivan Gau - Shalla

The cow has been a symbol of wealth since ancient Vedic times. However, they were neither inviolable nor revered in the same way they are today. Some scholars have argued, citing early Hindu scriptures and archaeological evidence, that the cow has not always been sacred and that cows, oxen, and bulls were both sacrificed and eaten in Vedic times and to some extent even later.
The cow was possibly revered because the largely pastoral Vedic people and subsequent generations relied heavily on it for dairy products and for tilling the fields, and on cow dung as a source of fuel and fertilizer. Thus, the cow’s status as a 'caretaker' led to identifying it as an almost maternal figure (hence the term gau mata). In addition, it has been suggested by author and orator Terence Mckenna that religious reverence for the cow is a result of early humankind's association of psilocybin mushroom with it, this association having developed as a result of the discovery of said mushrooms in the animal's excremen.
Hinduism is based on the concept of omnipresence of the Divine, and the presence of a soul in all creatures, including bovines. Thus, by that definition, killing any animal would be a sin: one would be obstructing the natural cycle of birth and death of that creature, and the creature would have to be reborn in that same form because of its unnatural death. Historically, even Krishna, one of the most revered forms of the Divine (Avatar), tended cows.
In therapeutic section of Charak Samhita (pages 86–87) the flesh of cow is prescribed as a medicine for various diseases. It is also prescribed for making soup. It is emphatically advised as a cure for irregular fever, consumption, and emaciation. The fat of the cow is recommended for debility and rheumatism
It is mentioned in Manu Smruti, in chapter 5 verse 30 “The eater who eats the flesh of those to be eaten does nothing bad! even if he does it day after day; for God himself created some to be eaten and some to be eater”
Despite the differences of opinion regarding the origins of the cow's elevated status, reverence for cows appears throughout the major texts of the Hindu religion.

In Gandhi's teachings
The Cow was also venerated by Gandhi He said: "I worship it and I shall defend its worship against the whole world," and that, "The central fact of Hinduism is cow protection." He regarded her better than the earthly mother, and called her "the mother to millions of Indian mankind."
Our mother, when she dies, means expenses of burial or cremation. Mother cow is as useful dead as when she is alive. We can make use of every part of her body – her flesh, her bones, her intestines, her horns and her skin.