Veterinarians, mammal breeders, etc. - what is birth order in litter pregnancies?

[CaveDave]

Howdy, folks.

An acquaintance asked me today about cats (dogs, pigs, mice, anything with normal multiple pup litters, I guess) delivering a litter of kits, is birth order related to the siring order in cases of multiple sires, or is it only a matter of which embryo implants where in the uterus, or some other factor?
Can each embryo have a different sire (in the wild)?
Is genetic blending possible, or is there only, at most, one sire per offspring?

Related but separate: a dog breeder once told me that to ensure pure-bred pups, if there has been a "visitor of unknown origin" at some point, that a long interval and/or certain number of "heats" must pass before the offspring are considered pure. Any truth there?
Is sperm in some way stored in viable form?

Cheers,
Dave

[casebro]

Only one sperm penetrates each egg if fraternal twins. It so happens that a pair of human twins was born just recently with two different fathers. I guess the mom passed two eggs. Just like a bitch.

Identical twins happens when a zygote splits, making two babies.

Fraternal twins happens from multiple eggs, in human, usually one father, different combinations of genes.

So, yes, mammals can have different fathers in the same litter.

In pure bred dogs, pups have to be "confirmed", examined to be sure they meet the specs for the breed. This is in case the Mom had a 'visitor', who may have sired parts of the litter.

No, I don't think the mom has to skip several heats to be sure the visitor's sperm is no longer viable. It doesn't life that long, she does have a 'period' like women to cleanse stuff out, and besides, the confirmation process will weed out any cross breeds.

[Rolfe]

Howdy, folks.

An acquaintance asked me today about cats (dogs, pigs, mice, anything with normal multiple pup litters, I guess) delivering a litter of kits, is birth order related to the siring order in cases of multiple sires, or is it only a matter of which embryo implants where in the uterus, or some other factor?
Can each embryo have a different sire (in the wild)?
Is genetic blending possible, or is there only, at most, one sire per offspring?

Related but separate: a dog breeder once told me that to ensure pure-bred pups, if there has been a "visitor of unknown origin" at some point, that a long interval and/or certain number of "heats" must pass before the offspring are considered pure. Any truth there?
Is sperm in some way stored in viable form?

Cheers,
Dave


Birth has to be in order of being closest to the cervix as far as I know. I don't see how overtaking is allowed. However, most litter-bearing species have two uterine horns and I think it's a bit of a toss-up which side goes first. You can get two presented at once, which is a right tangle.

Identical twins are unusual, but must have the same sire. Littermates which are not identical twins may have different sires if more than one male has mated with the dam during the relevant oestrus period.

I'm not sure about mixing genetic material. I have a feeling chimeras can occur if placental circulations get mixed up, but again I don't think it's common.

All that stuff about purebred females being tainted if a misalliance has occurred is so much old wives tales. There have been a few conicidences which reinforced the myth, but basically no, if a bitch doesn't conceive to the misalliance (say because you got in there with the morning-after injection in time) then that's the end of it. And if mongrel puppies are born then again that's the end of it. They used to have the same myth in horse breeding too. No, the "foal bed" isn't "tainted", you mediaeval horse-copers.

Rolfe.

[Toke]

[Not relevant for dogs]
I read of ferrets or somesuch where a male would raid a nest to mate with the young females.
The idea is that the eggs can be fertilised even in an underage female and their first litter, even if born much later, will be sired by him.

[casebro]

Yeah. well, I've heard of tribal humans presrving a pregnancy for years. In bad times, drought and such. Stopping fetal growth, then starting up the same pregnancy. I think it took some ritual and a dead chicken.

But I didn't believe that one either.

[Delvo]

I believe there are vertebrate species in which the females can either store a potential father's DNA for later, or stop and restart fetal development, or both. But none of them are placental mammals.

[CaveDave]

Only one sperm penetrates each egg if fraternal twins. It so happens that a pair of human twins was born just recently with two different fathers. I guess the mom passed two eggs. Just like a bitch.

Identical twins happens when a zygote splits, making two babies.

Fraternal twins happens from multiple eggs, in human, usually one father, different combinations of genes.

So, yes, mammals can have different fathers in the same litter.

In pure bred dogs, pups have to be "confirmed", examined to be sure they meet the specs for the breed. This is in case the Mom had a 'visitor', who may have sired parts of the litter.

No, I don't think the mom has to skip several heats to be sure the visitor's sperm is no longer viable. It doesn't life that long, she does have a 'period' like women to cleanse stuff out, and besides, the confirmation process will weed out any cross breeds.


Birth has to be in order of being closest to the cervix as far as I know. I don't see how overtaking is allowed. However, most litter-bearing species have two uterine horns and I think it's a bit of a toss-up which side goes first. You can get two presented at once, which is a right tangle.

Identical twins are unusual, but must have the same sire. Littermates which are not identical twins may have different sires if more than one male has mated with the dam during the relevant oestrus period.

I'm not sure about mixing genetic material. I have a feeling chimeras can occur if placental circulations get mixed up, but again I don't think it's common.

All that stuff about purebred females being tainted if a misalliance has occurred is so much old wives tales. There have been a few conicidences which reinforced the myth, but basically no, if a bitch doesn't conceive to the misalliance (say because you got in there with the morning-after injection in time) then that's the end of it. And if mongrel puppies are born then again that's the end of it. They used to have the same myth in horse breeding too. No, the "foal bed" isn't "tainted", you mediaeval horse-copers.

Rolfe.

[Not relevant for dogs]
I read of ferrets or somesuch where a male would raid a nest to mate with the young females.
The idea is that the eggs can be fertilised even in an underage female and their first litter, even if born much later, will be sired by him.

I believe there are vertebrate species in which the females can either store a potential father's DNA for later, or stop and restart fetal development, or both. But none of them are placental mammals.

Thank you all for your informative replies!

The concept of chimeras (from Rolfe) and the delayed pregnancy in ferrets (from Toke) are especially intriguing. I must try to follow up w/google.

I was asking about placental mammals, but Delvo's remark is ringing some kind of bell in the deep recesses of my mind. Could you be referring to snakes or fish by chance? I may have heard something along those lines years ago, if I could just recall...:o

Thanks much for the replies.

Cheers

Dave

[M.R.B.]

Bears (Ursidae) and stoats, weasels etc (Mustilidae) can all have embryonic diapause - delayed implementation of the fertilized egg.

Toke is referring to the stoat aka ermine (in North America).

Dogs do not.