An obese first calf heifer can also produce a very small calf. The fat around the reproductive organs limits the amount of growing space. One of the smallest calves I've seen was a bull calf born to a first calf 5 year old heifer (she had aborted a prior pregnancy). He was tiny and would have died if we had not been present. He, along with a much larger bull calf born a few days later to a two year old first calf heifer, went to the sale barn at the same time. I have pictures somewhere of the two together but I don't know where.