How much does a holstein cow weigh in lactation?

It depends in the breed!

If you are talking about dairy cows the average Holstein Cow weights 1,300lbs give or take a couple hundred pounds. But that is for a mature cow.

Dairy cows usually have their first calf at about 2 years old and not considered mature until they are about 5 or 6 years old!!!

Cows only start producing milk when they have their first calf.

Holsteins are the most common dairy cows in the world and the biggest and largest of the dairy cows.

Jerseys are much smaller for example!