puppy size difference - Page 1

I posted this question under a different thread but didn't get any opinions, so I started a new thread. A friend who breeds GSD's has this theory about the differences of puppy size in a litter. I'd like to see what other breeders think about this. She thinks that a large litter with big differences in size may have something to do with gestation (spelling??). Sometimes a male will breed a female over a period of 5-7 days or so. She feels that some of the bigger pups may have been concieved at the first breeding and the smaller pups concieved during the last breedings. In theory the pups in one litter could be almost a week apart in development. Could this explain why most pups even out in size at a later age. Opinions please!! Thanks, Melanie

Hi Melanie. All puppies in the litter are conceived on the same day, regardless of number of breedings and the time passed between breedings. Every breeder with "theories" should read this book: "Canine Reproduction: The Breeder's Guide" by Phyllis A. Holst, MS, DVM. This book is supported by scientific studies, I just loved it.

I have heard this same opinion expressed before and I have no reason to doubt it since we know for a fact that a female can have pups from two sires that were mated at different times. If there is four or five days between breedings it stands to reason the ones conceived first will be bigger at birth but since they have the same genetics, the size will probably more or less even out as the dogs mature.

von lotta, where did you hear from the "same day conception" theory? i'd be interested in reading; nature assures fertility by multiple matings; there are multiple ova to fertilize, and this is ensured by multiple matings; if there are different males mounting the same female, there's different pups in the same litter with different father; look at mutts that look like mutts but one of the sibling happens to be a rottie... get my point? kosta

Hi guys, "same day conception" theory is proven by lab studies, and I read about it in the "Canine Reproduction: The Breeder's Guide" book. About multiple breedings: sperm can live 5-7 days after mating, righ? So, say on day one the female is mated with the male #1, on day three she is mated with the male #2, and on day 5 she is mated with the male #3. Say, she ovulated on day three (this is when ALL the eggs are released for fertilization), and her eggs are mature enough for conception in two days after that. As a result, sperm of all three males is still there, alive, and a multiple-sire-litter will result, but all the puppies are conceived same day, two days after ovulation. There is only one ovulation in a dog in heat.

another consideration -- growth /size is regulated by GROWTH HORMONE -- that is to say the so called runt of the litter is also a fallacy -- the runt doesn't always have to be the smallest of the litter in the end when maturation is complete --

As you state this is an excellent book, Canine Reproduction- A Breeder's Guide, by Phyllis A Hoist, DVM: Alpine Publications, Loveland CO. However I would make one slight correction to your comment of fertilization occurring on one day. If you read in Chapter 5, "Stages of the Estrous Cycle" page 37; "...In years past, it seemed perhaps logical that because a bitch would breed for many days, and because breeding at various times was fertile, the process of ovulation must be prolonged, such as the release of one egg per day or something similar. But research has put this erroneous conclusion to rest. It has now been firmly established that all of the follicles ovulate within a short period of time." This backs up your point, but if you read on on the next paragraph. "...Three days are required for maturation to a second oocyte, and after the ova have reached this stage, the fertilzable lifespan seems to be fairly short. The lifespan of the secondary oocyte is twenty-four to forty-eight hours,..." This is not a big difference One day or two. So it is possible that you have a forty eight hour developement advantage in pups sometimes. How does this play into the Theory of size is open to debate.

If you do some homework I think you will find while you are on the right track, your theory is correct, your explanation requires some clarification. The smallest puppy may or may not be a runt and probably is NOT! A "runt" is, in fact, a "runt". A "runt" will NEVER attain normal size, health, looks, of the rest of the litter. Morgan