Cows determine the sex

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Alan

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First off, I know the bull determines the sex of the calf. But Dun's post on the 19 yr old cow got me thinking :shock: . His cow, at 19, has only had one heifer. I have 2 cows that out of 5 calves they have all been bull calves, I used 3 different bulls one them. I have 2 others that are both 2 for 2 for bull calves, 2 diferent bulls on them . The rest are fairly balanced heifer/bull ratio. Just to throw one more in the mix I have a mare that has had 7 foals, 6 colts and 1 filly. I wondering if there is any theories or facts to explain why some cows throw so many bull calves? Something to do with the cervex openings , position of the uterus? Are there cows out there that throw all heifers?

Thanks,
Alan
 
Here's a cut and paste from Wikipedia:

A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology. In animals, this is often accompanied by chromosomal differences. In other cases, sex is determined by environmental variables (such as temperature) or social variables (the size of an organism relative to other members of its population). The details of some sex-determination systems are not yet fully understood.
 
ok let me see if i can wrapp my brain around this for a min.since bulls sperm deteramine the sex of the calf.then it would come to reason a heifer/cow from a bull that sires mainly bull calve.would have the gene dissposition to produce all bulls when mated to a bull that gets mostly bull calves.we had a holstein cow that bever an i mean never had a heifer calf.no matter what bull she was bred to.
 
I think it has more to do with luck of the draw or maybe ovulation timing to breeding. She's also only ever had 2 red calves. One was the heifer the other is her current bull calf.
 
I have no idea how to explain it but I firmly believe that certain cows are predisposed to have a particular sex of calf. We have one cow that has had heifers at least 7 years running, records before that are kind of shotty. One of those heifers was co-twin to a bull calf, ended up being a freemartin. Thankfully, this heifer-producing cow is our best cow, I bought her in 1995 with a calf at side so who knows how old she is?
 
bigbull338":3b5umym4 said:
ok let me see if i can wrapp my brain around this for a min.since bulls sperm deteramine the sex of the calf.then it would come to reason a heifer/cow from a bull that sires mainly bull calve.would have the gene dissposition to produce all bulls when mated to a bull that gets mostly bull calves.we had a holstein cow that bever an i mean never had a heifer calf.no matter what bull she was bred to.

Bigbull388, I like your logic, unfortunately it does not work that way. The bulls sperm determine the sex of the calf through what are called the X and Y chromosome. All females have 2 X chromosome while all males have an X and a Y. If the sperm has an X chromosome then the calf will be a heifer. If the sperm has a Y chromosome then the calf will be male. So the effect will not be passed down through the generations.

Evidently the sperm with the X chromosome is heavier than the sperm with the Y chromosome. Therefore, it is beleived that the male sperm can swim faster and get to the site of fertilization sooner than the female sperm. However, the male sperm is also suppose to die sooner than the fermale sperm. This has led some producers, dairy in particular, to AI a little soon than recommended to try and shift the ratio in favour of heifers. I do not know if it works. If the above is true, logically it would follow that a cow who ovulates sooner in the heat cycle relative to standing heat would tend to have more bulls as compared to cows who ovulate later in the cycle.
 
We have a cow right now that as far back as I can remember (8 yrs.) She has had ALL heifers.....that is until this year.....we have recently purchased a new bull and she had a bull calf this year.
 
I'm not sure if this will help or not, but this info is true in humans not sure if the same applies in cows. The ph in the females reproductive tract has an affect on sex of offspring. For example sperm for a boy favers a alkaline environment so female sperm would not survive and female sperm favor a more acid environment so male sperm would die. Also timing of sex helps male sperm die sooner but move faster so close to ovulation you would be more likely to have a boy farther a girl because the girl sperm live longer but move slower.
 
I don't really understand this phenomena but I have a charolais x angus cross that has had 5 calves and the first heifer was last falls calf. Now she was bred to a Red Limi and had a black bull, bred to a black limi and had a red bull, bred to a black angus and had a white calf, bred to a black club calf bull and had a dark red bull, and finally bred to another black angus and had a black heifer. So figure that one out.
 
I do not have sufficient recall to site the sources but I have read research that indicated that some cows were able to to influence the sex of their offspring. this is not a consious decision type thing but is related to the chemical environment within the cow.

someone else cited pH as a factor. I think that it is one of several factors about which we and the cow are totally oblivious. the conditions which exist in a particular cow may favor the survival and movement of one sex chromosome carrying sperm cell or the other .
 
I have been told and am inclined to believe it that the cow determines the sex to a great extent by when in her heat she ovulates. In effect if she ovulates early in the heat she will produce more bulls since male sperm swim faster. Conversely if she ovulates a little later in the heat she will throw more heifers since by then the male sperm who don't last as long have petered out and what's left are female sperm.

I have no scientific proof but it sounds plausible to me.
 
Maybe at what time in her cycle she stands for the bull and how long she will stand. if she stands right of the bat or runs the bull all over the pasture first.
 
i always thought nature has a way of balancing things out. if you have more cows than bulls nature will produce more male offspring to even the difference. but gramps swore by putting vinegar in the water tank at breeding time to produce more heifers, 51% of his calves were heifers every year
 
If it's anything like what I understand about people, the first sperm to get to the egg is not necessarily the one that gets to fertilize it. The egg "chooses" the exact moment to allow the sperm to enter. I'm not saying it's conscious, just that the ultimate timing is determined by the egg not the sperm.
 
2/B or not 2/B":1ql8sonr said:
If it's anything like what I understand about people, the first sperm to get to the egg is not necessarily the one that gets to fertilize it. The egg "chooses" the exact moment to allow the sperm to enter. I'm not saying it's conscious, just that the ultimate timing is determined by the egg not the sperm.


I'm sure you're right but if the major sperm load at that point is predominantly male or female that will still determine who gets in
 
Katie":3p4pbz1l said:
I'm not sure if this will help or not, but this info is true in humans not sure if the same applies in cows. The ph in the females reproductive tract has an affect on sex of offspring. For example sperm for a boy favers a alkaline environment so female sperm would not survive and female sperm favor a more acid environment so male sperm would die. Also timing of sex helps male sperm die sooner but move faster so close to ovulation you would be more likely to have a boy farther a girl because the girl sperm live longer but move slower.

Bingo
 
I dont know if you guys read the news but i read an article yesturday saying that if women ate breakfast while pregnant they were more likely to have sons and other effects of the diet determing the gender of the child.
 
i started a grading up programe years ago with a small number of cows as my numbers grew i had to cul , culling was cows that had bulls went when i got to pure bred i had three female lines as they bred almost intiley females this was over 15 years or so , it ended up that i had to buy other lines just to get some bull calves , the same happened in a dairy herd i ran aswell same female families kept haveing females this happened in both herds with AI and natural mating so female lines if they are strong do seam to breed that way , and that was over a 25year period.
 

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