Cow vs Heifer BWs

[cmf1]

First two AI calves off of the same bull just hit the ground off of a 13 year old mamma and her 3 year old first time daughter.
Daughter bred 5/12/2012 calved 02/09/2013 273 days BW 45 pounds bull calf.
Mamma bred 5/12/2012 calved 02/13/2013 276 days BW 67 pounds bull calf.
Both pure bred.
Both calves up and running with no issues.
I expect the heifers calf to be lighter but this is my first year to actually weigh.
Is 30% a common weight range to differ from cow to first timer in your experience?
I'm not surprised or concerned, just curious. I've never looked at it in numbers before.
Thanks.

 

[randiliana]

I'll tell you more this year... Our heifer bull from the last few years was with cows this year. I think it will depend on the cow/s, but it is generally believed that a heifer will have a lighter calf than a cow. How much lighter, I don't know though.

 

[Lucky_P]

Typically, the 1-st timer will have a smaller calf.
Sure, these calves are sired by the same bull - but 'daughter' and 'mama' aren't full sibs; BW epds for those two may be quite different.

But...wife and I were looking over records this morning. Examined performance of several years' worth of data on some full-sibling calves(by the same bull out of same cow) for several years - often, there's a big difference in performance from one year to the next.
Kinda like my own kids - the eldest son is 6'2"/220#, weighed 9.9# at birth; #2 son is 5'11/150#, weighed 7.7# at birth. Same sire and dam, different genetic expression.

 

[shadyhollownj]

I raise polled herefords. 2 year old heifers I find will be 65-75lbs. 30 month to 3 year first calf heifers were 73-83. Cows were 75-90. Now that is based on management and Ai bulls selected.