Hi All, a puppy that i bred (not owned by me) went for her scan today. The scanner saw 5 pups but mentioned that they were all on the same side and the other side is completely empty. Is this usual??? My friend has been worried as her girl had a fall last week (26 days in) whilst chasing a rabbit on the field and fell on her left side which just happens to be the side that has no pups. Was just wondering if there could be any connection??

I think 3-4 weeks is when the embryos are attaching themselves to the horns, so I would guess it's possible, but I'm not an expert. Still, at least she has several in the other horn still.

Thanks Lucy, i wonder if the fall had caused the pups to be reabsorbed, if so would there be any evidence that this had happened??

We've had a couple of litters where the pups have been in one horn only.  We've also had a couple where one horn is full and the other only has one resident.  Guess its either luck of the draw where they all float to and embed or possibly the horn that is not used is not conducive to a developing pregnancy and any eggs that float into there cannot embed and continue into embryos/foetuses.

Embryos generally embed into the uterine horns around day 16 - 18 after conception; therefore, at 26 days gestation they would have already been embedded.  They are also very well protected from bumps and bangs at this stage of development.

I would think that if reabsorption was the issue, given how soon after the fall your friends bitch was scanned there would have been some visual evidence of pregnancy failure in that horn.  Most likely there were never any embryos in that horn to start with.

When one of mine had this scenario, the other horn had loads of cysts. That may be the reason.

When one of mine had this scenario, the other horn had loads of cysts. That may be the reason.

Yes, that could have been the reason.  If a horn is not quite right for any reason the some or all of the eggs can't implant or if they do implant they can't continue their development.  Scar formation, abnormal shape, cysts etc. can all be reasons why a uterine horn is not fully functional.  Good job they have two!  Mind you, there can be issues in both horns, all depends on what the problem is and to what extent the horn is "damaged".

I had a  similar scan last year with my girl.  There were two in one horn and one being reabsored in the other.  The scanner suggested that there could be a problem with horn.  Won't know if this is normal for her unless i mate her again next year.  Her line is of good litter size, so she wasn't normal.  I did wonder if it was because she kept jumping off the bed.

My other girl had one but i think she had KC in the first few weeks.  Who knows? for sure.

>I did wonder if it was because she kept jumping off the bed.

I honestly don't think so.  As someone has mentioned, the pups are well protected.  I took a pregnant bitch on holiday with me one year.  She ran under the wooden fence round the site.  And jumped!  It was a 10 ft drop onto a road.  She was fine, and pups were fine.  It was a large litter for the breed, so I don't think there was any reabsorption at all.

Pregnant women have been known to have bad falls onto their tummies with no ill effects.

It's wise to remember that all animals who have litters - as opposed to those that commonly have just one offspring (or twins/triplets as sheep do) - have a uterus divided into horns, thereby allowing many more embryos to attach and develop on the enlarged surface area of the two horns.

I think a secondary survival feature of these animals is that if one horn becomes damaged or diseased, then the other horn could still feasibly nurture enough young to qualify as a litter... in some cases much better as there will not be as much competition for space.

Thinking aloud here... it is well known that males can be born with one or no testes... and that is often hereditary. I am not sure how that translates to the female but if small litters are due to only one ovary working, could that relate somehow to males in the same line only having one working testicle?

There is one ovary per horn, and unlike human beings where both ovaries provide eggs to the one womb, in animals that have a horned uterus, each horn has a dedicated ovary... so if one ovary was defunct, then only the other horn would receive eggs.

It is a long time since I last sat a biology exam, so please correct me if I'm wrong! I would be interested to know if there is any correlation between reproductive failure in males due to missing/misplaced testes, and any anomalies in females.

>so if one ovary was defunct, then only the other horn would receive eggs.

You're absolutely right - and yes, it could be similar to monochidism in dogs (males). Do you know for certain that the ovary that supplies the empty uterine horn is even in situ, let alone functioning?

Majority of human females produce one egg per month from alternate ovaries.

When I was a midwife I took care of a woman having her fourth set of non identical twins, she obviously produced an egg from each ovary, the Drs offered to sterilise her but she refused, the oldest set was only 7yrs old, she was very relaxed about it, she had got used to juggling 2 babies each time.

I don't know if undescended testes and uterine abnormalities are connected in a line.

Litter sizes seem to run from mother to daughter although the bitch I bred had 6 pups but her dam and granddam only had 3 or 4 from 2 litters each, I am waiting to see if she does the same with her next litter.

>Majority of human females produce one egg per month from alternate ovaries.

Yes, but the eggs from both ovaries go to the same single-cavity uterus; the bitch reproductive layout is different.

I realise that.