A calf raised for baby beef can be slaughtered between 5 and 8 months of age, and a calf used for veal can be slaughtered from 2 weeks to 3 months of age.3 people found this useful. Karin L. This is my specialty.he average weight for all cows is around 1400 to 1600 lbs. However, a cow of any size and weight can be slaughtered. She can be as small as only 700 lbs, or as large as over 2000 lbs.