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Question for people who run one bull only with cows.........

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Well-known member
Sep 25, 2006
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Eastern Colorado
I know the sex of a calf is determined by the sire, but I am curious what everyones experience is. Do you see many bulls that sire more bulls or more heifers consistently, year after year? I have suspected bulls of doing that, but not able to pinpoint sires, I can't prove it.
I was told it has to do with timing. Heifer sperm swims faster but dies quicker is what I was told. I guess if the bull is exactly on time or a little late you are more apt to get a heifer, but if he is a little early you are more likely to get a bull.

My bulls must consistently be early because I get a lot more bulls than heifers on most years, sometimes running over 70% bulls.
Time of breeding is what decides it. Changes in hormone levels allow for bulls early in the cycle and heifers late in the cycle.

When we did A.I., we consistently bred late in the cycle for heifers to build the herd and the neighbor was breeding early because he was trying to sell bulls.

Generally, if I can't catch the bull doing the deed or the cows in standing heat, I assume there will be a large percentage of bull calves.
Female semen is lighter than male, that is how sexed semen is accumulated. Also females live longer ,but males are more aggressive, So if you breed early the male will swim like hell but die before they accomplish the job where as the female will swim diligently and still perforate the egg. IN THEORY.

Or I could have forgotten my UNI courses and be all wrong :p
My old herd sire has consistently produced 2 female calves for every male over a period of 5 years. Why? Don't have a clue. It's just what the numbers show.
I was wondering the same thing. This year out of the first 20 calves that where born I had all heifer calves, then it started to even out some but out of 150 head I ended up with over half heifer calves. Now last year it was completly the other way.

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