Is it a Myth or Not

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Feb 4, 2020
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Ok is it true that if you breed a heifer at 12 months that it will stunt her growth?
Yes you should wait till there 18 months but it does happen I have some that are five and are there normal size and the first calves were born ok and normal size
I bred my Hereford/Jersey heifer at 13 months because she had crrrrrazy heats, and I felt I was in danger! She'd run up behind me and jump on me, seriously. So I sent her to the bull at 13 months, and it definitely did NOT stunt her growth. She grew into a very large, very healthy cow. She weighed about 1,600 pounds at maturity. (But I also made sure she never missed a meal. She was my milk cow.)
For me the ideal time to breed heifers as far as English or most continental would be 14-15 months to calve at 23-24 months.
Like @Caustic Burno stated Brahmans as well as some continentals mature later
Over the years I have bought several young heifers that were already bred as well as some that I had raised that got bred before they were weaned.
That would put them at calving at 15-16 months or so. That’s certainly not ideal, but more often than not it’s ended up pretty well for us.
My game plan for those heifers is to feed them a long to help them grow and develop, but not get them fat.
After calving, I usually run them with the heifer group, or a smaller group that I am still feeding along. Those young heifers are still growing and raising a calf so they need some extra feeding to help them along. All of the heifers that I have done that way have turned out to be the same mature size as their herd mates.
@Lannie we have a young Jersey heifer now that is 7-8 months old and coming in heat like clockwork, you know she’s in when she bawls and runs nonstop for a couple of days.
Personally I like to let our heifers grow and calve as 2 year olds . I definitely think you affect their size by breeding them young . But if you feed them good you can definitely help them . Pulling their first calf sooner than you normally would also helps . The problem some experience is getting them to breed back after their first calf . Big demand on that heifer ; calving , feeding her calf, growing, and then breeding back .
As far as being stunted by being bred and calving young... I doubt that case can be made consistently. Maybe some... but maybe they were going to stop growing anyways.

The worse stunted cattle I've seen were either battling disease or severe malnutrition at some point in their early years. Well I guess there are also the inbred and deformed but I don't think that's what you are concerned with.

The best cow I've ever seen for calf weight to cow weight ratio at weaning was a stunted Holstein with a big head and a tiny body. The neighbor up the road had the cow and she would be bred to a good beef bull and raise a calf as big as she was at weaning time. I'd say she was 700 pounds and she'd raise a 700 pound calf. Butt fugly cow but she was a calf raising machine...
What Travir said is true . I have a friend who has a herd of smaller cows . He breeds them early and wants a cow 800- 900 pounds . He says my cows are too big . My cows eat more being bigger and require more hay and grass . His calves are a little smaller than mine at weaning but are good calves . My point is : other than our friend from Lithuania with her 100+ birth weight calves our objective is raising cows that calve regularly and produce live healthy calves regardless of momma’s size .
My father and myself have always bred heifers in the 14-15 month range -- calving at 2 years. That is a pretty common practice in this region.
900 lb cows on the other hand are not common practice. Having invested in scales a few years ago -- I can say that a 5-yo leather and bones Jersey cow will still weigh 1,050. And small to moderate angus cows at BCS 5 are still 1,200.
It not a guarantee but it can effect development of both the calf and and the heifer. There could be short term and long long term effects. Just affecting a few heifers or a few calves would negate any gains from breeding 4 months earlier. It's a risk vs reward scenario that doesn't pay.
One of my oldest and best cows currently is a commercial Simmental that was purchased at around 500 lbs as a heifer to go into our bred heifer sales. Turns out she was bred when I bought her, and she calved at the time her mates were being bred. I couldn’t sell her in the sale so I kept her. She is dependable and raises a big calf, usually the biggest and if not it’s close to it. She is going on 12 and just tonight found her with a calf. She always gains time if running with a bull soon after calving.
She had a daughter by a registered Angus that got bred before weaning and she has matured into a really nice looking big framed cow, she doesn’t have quite the record her mother does though, but she has calved every year.
I breed 'em. Better to have them calve out of my bull versus one of the neighbor's bulls jumping fence. I have nightmares to tell on that.

I have hauled smaller ones to my home (small pasture there) as a fail safe.
I had a heifer get bred at 4 months and calve 4 days short of 13 months old. (Not planned obviously). She went on to raise 3 more calves before I had to cull her for a bad attitude at 4 years old. She was normal size and if it stunted her growth I could not tell. She weighed 1420 pounds when she weaned that 4th calf. Perhaps she would have been 1600 pounds if she had not calved as a yearling. We will never know. I breed all my cows to calve at 2 years, so most are bred at 14 to 15 months. I would not think 12 months would have much impact on growth, but some may not be cycling yet. I expect most would be though.

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