wow that is lovely that you had strong bond with them. Yes Veganism is the way if you source your diary products from stores. But if you have just a few of your own cows and they are allowed to be cows naturally and you make your own diary products out of necessity to sustain your family then vegetarianism is ok! except the potential health problems associated with diary but still would be alot less contaminated than store brought. But the cow must be treated with respect for providing its life giving sustenance and there should be enough for the calf as long as it needs it.