Yes, cows are holy indeed.
Reasons to keep a cow in a family:

1. Cows maintain a spiritual environment in a family; it means less stress, prevalence of love, care, and understanding amongst family members. It has been proved and verified that a person who stays in the vicinity of a cow for 30 minutes everyday will effortlessly and unknowingly develop positive attitude, intellect and righteousness; in a research, results were seen clearly in a period of two to six months.

2. Cows help maintain a healthy environment. If a person has problems of blood pressure and sugar levels, he should rub his hands on the cow’s hump for 15 minutes everyday. In six months time, the patient will be cured completely. It is not clear how many other diseases can be cured this way; more research is underway.

3. Cow’s dung and urine have numerous medicinal values; a 90 year old man testifies the fact saying that he had never took any medicines in his entire life other than cow’s urine for all diseases. At 90, he’s as healthy as a youth.

4. Cow dung produced by just two cows is sufficient to produce enough bio-gas for cooking, and lighting a 60 W lamp for a four-member family. The dung-slurry which is a waste from the fermentation serves as a rich natural manure for farming.

5. A family that gets to drink enough cows’ milk will not suffer from malnutrition; cow’s milk and its products have high nutritional value. The milk can also be sold for additional income.

6. The Vedas regard a cow’s body as the dwelling of the Gods and Goddesses in subtle form; since I cannot provide proof of this, I shall not debate on it. Based on the above facts, I will just conclude that a cow does hold positive energy in her.

Unfortunately, the world has been killing “Goumata” (Mother Cow) for beef. There’s no need to explain what we’ve achieved or where the world has reached by doing so- unrighteous people, greed, disease, hatred, poverty, malnutrition,………. We all know !

Source: Pandit Shri Ram Sharma Acharya

A pandit as a source won't get you too far in the scientific world!

so this is why cow is so sacred in Nepal???.........im not gonna say another word I can feel the haters cursing me already..... nice one III_III ...peace out

You've very right brother. The validitiy of the entire Pandit tradition has been at risk, and come up as a mere money-making profession. But this guy "Pandit Shri Ram Sharma Acharya" is more than that. Initially, I thought that he was just one among the various "bahuns", but really, he has written more than 3200 books, and gave his entire life earning for the society. He has become my role model brother. His thoughts are really life-changing, and we can gain a lot from his knowledge to uplift our spiritual life. Seriously !

http://literature.awgp.org/hindibook/ThoughtTransformation/LokSeviyoKeLiyeDishaBodh/

About number 4: They produce more mithen ( may be not correct spell) gas therefor researcher are tryig to add indian spice specially cumming in their diet to lower down , regarding lower down the sugar and blood pressure , when you rub your hands 15 minutes to their hump , it is quiet a bit exercise and the position may make positive difference , and results are positive.
Holy or not,  ancient people knew it and took a good care of it. To preseve more they make it part of the religion.

@ Bairagi kailo: Well said brother! I agree with you.

I agree.....most do's and donts in any religion are mostly man made rules to control people by installing fear to follow right v/s wrong in promise of heaven v/s hell. Thats all.