Karin'
It took me a few readings-over to finally figure out what you were trying to say.
That has always been a problem of mine. Believe me, I can verbalize it much better then I can write it, so please feel free to ask question if I am not clear.
I only got an A-, some years back, when I did a paper on this exact subject for that exact reason.
The foot note read: Excellent on the facts but you failed to communicate them, I will never forget those words.
The problem with this statement and the rest of your posts is that it didn't take into account the time a cow needs to involute her uterus.
It sure does. It's in the variance and recuperation time.
Variances = 14 days
Recuperation and recycle time = 30 days ( with variances 44 days )
Sure a cow can come back into heat two to three weeks after calving (approximately), but that doesn't mean that she's ready to breed right after calving.
True, but it also doesn't mean she is not ready to breed. It has been reported that cows have breed as early as 11 days and breed after giving birth, on the low end. But that is rare.
Still on the low end generally 30 days is the rule of thumb.
Those that come in heat under 30 days usually end up being a false heat and she will come back in heat in 21 days. The chances of a heat being a false heat is almost nonexistent after 60 days after birth, unless something other than birth caused it.
When a cow is in false heat she will have or exhibit every sign on a real heat except she will not let the bull achieve penetration. Even a bull can not tell the difference and will mount her as do other cows in a SAG.
Everyone on here, and I'm sure you do as well, knows that a cow needs at least 45 to 60 days of rest (being time to be open) before being set to breed and be pregnant again.
I don't agree, some maybe, but I don't see 30 days as being unreasonable when nature is allowed to take its course.
But what is interesting is, you have now plugged in a 15 day variable yet you object to me using variables. To reach your starting point of 45 days, I used 44 days.
Sounds to me like we are in agreement on that one.
And of course, in order for a cow to calve on the same day as last year, this rest period has to be a little less than twice as long as 45 days.
OK, but lets try saying it this way.
The time a cow must be open, to produce a calf each year on the same date each year
is 82 days, with no variable.
Is not 82 days "a little less than twice as long as 45 days."
Sounds like we are in agreement on that one also.
So the bottom line is:
To produce 1 calf per cow on the same day each year you MUST leave that cow open for approximately 82 days.
And if you have 100 head of cows, that's 8,200 days or 273 months or 22 yrs of non production in just one year for the total herd.
Now to address Tncattle's problem.
You only have two options, sell them and replace them with bred cows in sink with your herd or leave them open to your next breeding season, but don't think this will finally put an end to your open cow problem.
Because any variable can put your cows, new or old, back out sink.
It's just a matter of time as variables magnify each and every year.
That is why those using this management procedure must also use a clean up bull.
MW