Dual-horn Pregnancies

[MamaSheepdog]

Sometimes this means that she will kindle at intervals

Have you ever heard of that being successful, Maggie? I would think with one litter more mature than the other, the youngest would not be strong enough to compete for milk. Just curious- not something I want to try personally!

Here is another thought that has occurred to me: it is so common to have one or two kits in a litter that are "runts" that I wonder if they are a result of fertilized eggs in another horn a day or so later- I have heard that "male" sperm are faster swimmers but not as long lived as "female" sperm, with motility lasting about 72 hours. It would be interesting to see if the runts are more commonly female to support this.

 

[MaggieJ]

I have never seen this, MamaSheepdog, because when my rabbits were in cages I never did later breedings. If the buck fell off, even once, I considered the doe bred... and had very few miss. I've been hanging out on rabbit forums for a long time, though, and have heard of the occasional case where the doe did care for two litters of different ages. In these rare cases, the doe built a second nest and fed the litters separately.

I think it quite possible that what seems to be a few runts in a litter could be the result of later breedings. I see no way to pursue this theory, however, since it is not a practice I would recommend.

 

[ladysown]

I have to admit to being somewhat skeptical about dual pregnancies. WHY?

Because I've had occasion three times now to kill rabbits that were pregnant.

Bred one day only.

Doe one: started to weave around three days before due, date due I didn't like the looks of her so killed her. Had seven kits.. three on one side, four on the other.

Doe two: Found her dead, cut her open, all babies were dead.. six on one side, seven on the other. Would have been a huge litter.

Doe three: one tiny singleton kit.

So as much as they have dual horns.. and I hear time and again that they can become pregnant twice, Where exactly is the proof on that? It doesn't seem to bear out upon autopsy.. kits are found on both sides in two of the litters.

Is it because kits can be born in various stages of development?

Well I get litters born with kits in various stages of development or perhaps in process of being reabsorbed due to death in utero. this with the knowledge that I ONLY breed my does one time. Two - three mounts.. I don't breed back six hours later or anything. One breeding, take or not take.

 

[MaggieJ]

I don't have any proof. It may be hogwash, just like the "don't touch the kits" idea. I can't even remember where I first heard about it. I never felt inclined to test it.

I think in most cases does are stimulated to have both ovaries produce eggs and therefore one finds kits on both sides. Perhaps those disappointing litters of two or three are the result of only one ovary producing.

 

[OneAcreFarm]

I think it likely could be that the doe *could* get pregnant only in one horn, and if rebred days/weeks later, *could* get pregnant then in the other. I mean, it sounds plausible, but like Ladysown, I have had to open a doe and found kits on both sides as well.

 

[MamaSheepdog]

I think it quite possible that what seems to be a few runts in a litter could be the result of later breedings. I see no way to pursue this theory, however, since it is not a practice I would recommend.

You misunderstand me, Maggie. I am thinking later fertilization from the original breeding, since sperm are viable for at least 72 hours (at least in certain species- not sure how long for rabbits), so the runts might be from eggs released at a later time. Of course there is no way for a layman to check the theory, (except maybe by a higher incidence of female runts), I just felt it was an interesting theory to mull over.

I've heard of the occasional case where the doe did care for two litters of different ages. In these rare cases, the doe built a second nest and fed the litters separately.

Wow- busy doe. I'm surprised she wouldn't just abandon one nest altogether.

.. kits are found on both sides in two of the litters.

It appears to me that eggs can be released either unilaterally or bilaterally from the horns, with small litters resulting when only one ovary releases eggs. This might be verifiable by those who are skilled at palpation, which I most definitely am not.

In horses, implantation occurs at 16-18 days post fertilization, with the fertilized egg bouncing around the horns and uterus until then, and typically implanting near the base of one horn. I have no idea how this translates to rabbits, cats, or dogs, who carry multiple young in the horns of the uterus, i.e. do fertilized eggs sometimes migrate to another horn before implanting?

 

[Secuono]

The X sperm (which are the sperm that make females) live longer than the Y sperm (which are the sperm that make males). However, the Y sperm swim faster, so the chances are equally good that you will get a girl or a boy. If the Y sperm swim fast enough before they die to fertilize the egg, then you'll have a boy. If the Y sperm don't reach the egg before they die, chances are an X sperm will get there shortly, and then you'll have a girl.

found this on wiki.

 

[MamaSheepdog]

Exactly. Some people try to influence the sex of their babies by timing intercourse according to ovulation- a couple days early if they want a girl, and closer to actual ovulation if they want a boy.

 

[Frosted Rabbits]

One must also realize-- that rabbits are stimulation induced ovulators, but it takes TIME for each ova to be released. The number of ova released will depend on the stage each follicle is in at the time of stimulation--NOT ALL THE EGGS WILL BE RELEASED AT THE SAME TIME!!! And as fast as the kits develope in utero, just a days difference in fertilization can account for a BIG difference..

Now, folks, a peeve of mine--

Basic Mammalian Reproductive Biology--101

Horns and Fallopian tubes are NOT the same thing!!! A horse has ONE UTERUS--like ours are-- SINGLE-- A "One Room" Uterus, two fallopian tubes, two ovaries. RABBITS , Camelids, Cats, Dogs--- ONE Uterus, which is Bifurcated (branched, or split, if you will) into two HORNS- each horn has a Fallopian tube. There are two ovaries. Fertilization in most cases occurs near the entrance of the Fallopian tubes, but may sometimes occur closer to the uterus. This too, can affect the boy/girl ratio-- as in, how close was the ova to the Fallopian tube when the sperm were actually available. Where within the tube was the ova fertilized-- In some cases, the pH of the does body chemistry can also affect the boy/girl ratio.

A short quiz on this information will be given on Wednesday

 

[MamaSheepdog]

In equines, there is the uterus, which branches into two horns, at the end of which are the fallopian tubes, terminating at the ovaries. I should have a horse placenta very soon and I will share pics. In dogs and cats, the embryos are spaced at intervals in the horns, while a horse embryo usually attaches near a horn, but develops in the uterus itself. (The uterus is shaped roughly like a 'Y' or a 'T' with the body of it being the uterus, and the branches being the horns- the fallopian tubes are minute in diameter compared to the horns.)

It is postulated that horses cannot carry twins due to placental insufficiency- there simply is not enough surface area available for two healthy placentas. If a horse does carry twins to term, the foals are often emaciated, and often one or both do not survive. In a study done on outcomes of twin pregnancies in thoroughbred mares, 64.5% aborted both twins, 21% birthed one live foal, and 14.5% had two live births. The survival rate of the foals was not included in the data I viewed of this study. (I referenced the material I got when I took my AI course at UC Davis to provide this info.)

 

[akane]

I don't think a dual pregnancy is an even split between horns but a mix. Like you can get in other animals sometimes where 2 males breed one female and you get pups or kittens from both fathers but they aren't divided with these here and these here. They are mixed about in the uterus. If they were only within a day or 2 of each other it is possible you could get 2 litters with a litter of runts that might survive. Beyond a couple days I doubt the secondary breeding would survive and all the kits would be too underdeveloped to live. Having 2 births isn't really likely if even possible since first off like I said I think they are scattered about and 2nd that theory plus others supports the entire uterus emptying at once when they go in to labor and not part of it and then another part a few days later.

 

[MaggieJ]

Hmmm... Sounds reasonable to me, Akane. I was thinking that only one ovary at a time would be stimulated in these cases and that the embryos would be in separate horns... but it could well be the way you describe.

 

[MamaSheepdog]

I have no idea how this translates to rabbits, cats, or dogs, who carry multiple young in the horns of the uterus, i.e. do fertilized eggs sometimes migrate to another horn before implanting?

I researched this question, and the blastocysts can travel between horns before implantation in dogs and cats.

Here is a link to an article on placentation of rabbits... http://placentation.ucsd.edu/rabbitfs.htm

Some of the scientific jargon will make your brain ache- basically, it says ovulation occurs about 10 hours post breeding, and in one study "They showed that "alien" eggs catch up with the transport of normal eggs rapidly and they reached the uterus within 6 hours." (I have no idea what they mean by "alien" eggs...) The eggs implant on day 7.

I didn't find answers to our other questions though.

 

[Frosted Rabbits]

fertilization generally occurs within the Fallopian tubes, but yes, the target can and do travel across the abdominal space to the opposite Fallopian tube---( my sisters third child is a result of that travel, one fallopian tube removed, and the opposite ovary removed-- she thought she would never have to worry about birth control-- Surrr-prise- along comes child number 3.

 

[MamaSheepdog]

I hope she finds #3 as much of a blessing as we find Colliepup! He was a surprise also, but not on that scale! I still have all my parts- but Hubs was content to stop with our first two. (I'm glad Mom told me to poke holes in all the... well, you know! <kidding!>) :lol:

I can't imagine life without my littlest pup- and everybody absolutely adores him. He really is special.

 

[Frosted Rabbits]

yeah-- all three girls are spoiled brats, but number three is definitely the Diva. However, at 10 years of age, she does have quite the brain, and can do Masters level math easily--- She was born on December 7th-- hence her name, Victoria, we call her "Tory" EVERY aspect of their lives is controlled by my sister-- poor kids....