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What Influences a Puppy Litter Size?

↯ Key takeaway points

  • The size of a puppy litter is hard to predict and is dependent on several factors, including the size of the dog's body and breed.
  • The age and health of the female dog, as well as the quality of her diet and genetic background, also influence the size of the litter.
  • The first litter is usually smaller than the following litters, regardless of the age of the dog or its mate.
  • Inbreeding and limited gene pools can negatively affect litter size, while a younger stud may produce higher-quality sperm that can result in a larger litter size.
  • It is almost impossible to precisely influence the size of a puppy litter, but a dam bred between 2 and 5 years, in good health and on a quality diet, is more likely to have a larger puppy litter size.
Breeding Business is passionate about all sorts of domesticated pets. They have written dozens of articles across the web.
Licensed veterinarian and animal behaviorist with over three years of experience and a Ph.D. in Poultry Science.
Published on
Sunday 12 March 2017
Last updated on
Tuesday 27 June 2023
litter sizes in dogs
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The size of a puppy litter can be influenced by so many different factors, including random circumstances. Therefore, it is almost impossible to predict. Despite what you might have read, you will never know exactly how many puppies a pregnant female will be carrying until she is examined by a vet.

Scientifically, there is no such thing as “a fertile bitch, even if a breeder with experience states they recognize the signs of increased fertility in this individual. A lot of breeders think some females are more fertile than others. No matter how your bitch acts or looks, not even experts can be 100% sure about a bitch’s general fertility and an estimated puppy count. No matter how your bitch acts or looks, not even experts can be 100% sure about an estimated puppy count.

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Average Puppy Litter Size

There is no such thing as a normal puppy litter size. Usually, the size of a dog litter is mainly based on the dog’s body size — simply because biologically, bigger bodies are able to carry a larger litter size than smaller bodies. The litter size also depends on the breed of the female. Some small dog breeds will only bear one puppy at a time; we call these singletons.

Here are a few breeds and their average litter size:

Mother nature generally has her reasons and therefore made it so dogs rarely produce more than they can handle. Overly large litters may become a problem of their own. Having a larger litter may cause delivery problems with exhaustion and stillborns. It is harder for a female to feed the entire litter, and for herself to stay hydrated, and for her to eat enough to be able to nurse them properly.

Now, breeders often want to know how to influence their puppy count to lean towards the higher number in the predicted range. Let’s say for your breed the average litter size is between 8 and 12 puppies, some breeders want to help their dam get to 11, 12 or even 13 puppies.

Let’s see if and how this is possible.

Factors Influencing a Dog Litter Size

Now, even if it is extremely hard (if not impossible) to determine and actively decide on the size of your next puppy litter, several factors can influence with more or less weight a dog litter size.

Let’s review these factors below.

Inbreeding Effects On Dog Fertility

One of the most forgotten factors affecting the size of a puppy litter is the influence of a high coefficient of inbreeding.

The Institute of Canine Biology published a chart illustrating the comparison of data taken from the litter size of six particular breeds of dogs from the records of the Swedish Kennel Club: English Springer Spaniel, Golden Retriever, Labrador Retriever, German Shepherd, Finnish Hound, and the Swedish Elkhound.

Inbreeding effects on canine fertility
Inbreeding effects on canine fertility (chart by Institute of Canine Biology)

Although the results are relative, it clearly shows that the more inbred the puppies are, the smaller the puppy count will be. Usually, when a dog breeder uses a close inbreeding or linebreeding, it is to fix some desired traits but the price to pay is a much smaller litter.

The Breed

The breed of the dog makes a huge difference in litter size. Generally, it is known that the smaller the breed the smaller the litter size and the same goes for larger breeds, larger the breed larger the litter.

For example, Spaniels and retrievers usually have anywhere from four to eight puppies at a time while on the other hand, while smaller dogs such as a Terriers can only have two maybe three in a litter.

Age of the Bitch

The female’s age is a major point in determining the size of a puppy litter, and this is factual. Usually, dogs under the age of seven will have smaller litters than those that are of old age – but they should never be bred too early or too old. The very first litter, no matter the age, will usually be smaller than the others to come.

If a female is not bred until after the age of 5, she may have smaller litters permanently in terms of puppy count. If she was bred earlier than 5 years then she will probably have a slightly larger litter size. Dogs who are between 2 and 5 years usually make the largest litters.

The first heat in a female dog is usually between 6 and 18 months. The AKC recommends that females should be bred in their second or third heat for good dog welfare (and not before). Females, at that fertile age are at their fertility prime time.

Age of the Stud


The age of the male will affect the size of a litter but much less than the age of the female will. When a male dog gets older, his sperm count and the quality of it will decrease. Larger litters will most likely occur when the male dog is under 5 years of age as it is easier for the sperm to enter the female’s eggs, and the majority of the sperm is of a higher quality.

This is why the most famous dog show champions are bred extremely often and intensively in order to impregnate as many quality dams as possible. But this can lead to the popular sire syndrome.

Health of the Dam

Health plays a vital role in litter size. In summary, both parents need to be in excellent health to maximize their chance to have more puppies.

Dogs that are not genetically sound and healthy will inevitably tend to have a smaller puppy count. A healthier and slimmer female’s chance of a larger litter is greater than those who are overweight. Adding in a little more protein or extra protein supplements to the diet during pregnancy will greatly reduce the chance of having a smaller litter size. It is best to feed the female dogs high-quality dog food with no supplements.

Diet of the Dam

A female fed poorly will not give her body the required support in order to produce a larger litter; therefore, providing a quality diet throughout the year is key to your female’s health and, well-being, and thus improves her fertility.

In a study by Russ Kelly, a renowned nutritionist, three dams were fed three different diets:

  1. One dog was given top quality food.
  2. Another gave the same food as the first but with a supplement of cottage cheese.
  3. The last one was fed the same food but with rations of cottage cheese and meat.

A balanced diet without any supplements produced the largest litters. Diets too high in protein seemed to produce smaller litters. High doses of supplements (e.g. cottage cheese) may have caused fetal abortions.

The study’s findings were that supplementing top quality formulated dog food along with small rations of cottage cheese could increase the size of the litter at a health cost.

Size of the Gene Pool

Breeding in limited gene pools, such as dogs coming from smaller breeding groups where genetic diversity is very limited, is known to produce a (much) smaller litter size of puppies.

Many traits have high heritability, but fertility is definitely not one of them. Heritability has about a 10-15% influence over litter size, this means that one cannot rely on genes for increasing the size of the litter alone.

On the other hand, it is useful for dog breeders to know inheritable traits in dogs such as:

  • Coat color
  • Eye color
  • Size

You cannot put two parents who produced large litters previously and expect the puppies to also produce large litters two years down the line.

Infographics showing the factors influencing the size of a puppy litter.
Factors that influence the size of a puppy litter. An infographic by Breeding Business.

Can the Breeder Increase the Size of a Litter?

Breeders have had light success in influencing puppy counts by using different techniques such as selective breeding and pedigree analysis. It’s hard to know whether these successes resulted from pure luck or actual biological or physiological mechanisms that increased the puppy count.


Things such as diet, breed type, and health of both the mother and father will definitely influence the size of the litter, but nobody knows to what extent.

A dam bred between 2 and 5 years, and fed a quality diet, and in perfect health and top nutrition, is more likely to have a larger puppy litter size than a malnourished female. A stud of a younger age is more likely to produce high-quality sperm, which in return can have an outcome of a larger litter size.

It is important to keep in mind that no matter the age of the dam or stud, the first two litter will often be smaller than the following ones.

Are X-rays Safe for Pregnant Dogs?

Radiography is a non-invasive, painless, and safe procedure for dogs. Since radiography or X-ray’s radiation level is low, it is safe for pregnant dogs. However, it should be done after the first to the second trimester of the dog’s pregnancy.

It is also safe to talk to your vet first before doing the procedure. This will help you understand the risks of X-rays to your pregnant dog.

What Is a Single Puppy Syndrome?

In a very rare situation, a mother dog can give birth to a single pup. It is often called a “singleton” puppy. This situation can cause several behavioral challenges in a puppy. A puppy’s first teacher is its mother and they also learn a few things from their littermates. However, without their littermates, there are things that they will not learn early on, such as socialization, lack of bite inhibition, poor impulse control, and so on.

Singleton puppies should be trained at an early stage to make sure that they are still growing and developing at a proper pace.

The bottom line is that influencing the size of a puppy litter is almost impossible if you want to do it precisely. Otherwise, you can follow all our pieces of advice above and put all the chances on your side, but nothing is sure.

Read more quality articles about dog breeding!

17 comments on “What Influences a Puppy Litter Size?”

  1. Regarding the section called “Age of the Bitch” – could you please let me know your source of this information? (e.g. The journal article?) Thanks!

    1. Hello Tegan – nice to read from you! This is from the study named “Litter size at birth in purebred dogs—A retrospective study of 224 breeds” from Kaja Sverdrup Borgea, Ragnhild Tønnessena, Ane Nødtvedta and Astrid Indrebøa – the PDF is available online for free.

      1. Thanks for quick reply! I’ll get to reading it now.

        1. Interesting study, nothing new or unheard of before but good read. Our articles also rely on breeders’ perspective(s) on a given topic or section. Not always scientific nor does it need to be me thinks!

          1. Terri Smith

            It’s hard to believe any of this litter size info. My Golden girl was one of twelve puppies in a first litter for her mom, now my pedigree golden is also pregnant and in 10 days, we will be seeing the vet again for guessestimate on number of puppies. This first litter is smallest is not true, my first golden had 10 healthy beautiful puppies 20yrs ago and 3 her last breeding.

  2. ogunmodede ademola aaron

    I think timing of breeding too matters in factors affecting the litter size, likewise the case or absorption or abortion of some foetuses by the dam and wouldn’t know if truly litter size can be hereditary would like you to look more into this. Thank you, what a good wrote up

  3. Anna

    i’m curious about giving bitches extra calcium during pregnancy. The article states according to a study done, bitches that were fed cottage cheese and additional protein, on top of a good diet, is recommended. My vet says never to give extra calcium during pregnancy.



  4. Sherry

    At what age should you stop breeding a female. And how many c-sections should the limit be

  5. Tricia

    I believe that the results of the nutritionist Kelley were misquoted for this article. On reading other references to this article, it is my understanding that the litter size was in fact largest for those bitches fed a high quality commercial food WITHOUT supplementation. Could you please post a link to the original article so we can fact check?

    1. Jackie

      I agree, it said cottage cheese not recommended.. I’m confused?

  6. Linda Roulston

    Interesting article and summary! I was not able to access the original study since the link is giving me a 404 message. I believe you need to edit this sentence… “Usually, dogs under the age of seven will have smaller litters than those that are of old age” … since it causes confusion and conflicts with the later statement … “If a female is not bred until after the age of 5, she will have a smaller litter size. If she was bred earlier than 5 years then she will probably have a slightly larger litter size.”

  7. Wendy Lever

    Interesting article, but please review the section detailing the findings of letter size in response to supplementing with cottage cheese and meat. In fact contrary to your conclusion that litter size is increased they are in fact decreased with supplementation. Litter sizes were bigger in the group fed only a high quality dog food.
    This is evidenced by the original article produced by the researcher and nutritionist Russ Kelly

  8. Shiba Inu

    Also having the mating at the end of the fruitful period of the female bitch and not already from the beginning is a factor that leads to having more puppies. Try to deepen this very but very important aspect too.

  9. Steven B.

    we got a female brindle pit bull and she got pregnant at 13 months by another pit bull next door Well after a rather long time 75 days after she went into labor and within 18 hours out came 13 births of which 1 was stillborn another was very week and not at all healthy who died the following day still another from mysterious causes But the remaining 10 are very good and thriving and they are too cute for words Interesting is that there is 1 who is by far the biggest and takes up the most titty time and the boss and 1 runt The sire is a young about 2 year old American Stafferfordshire pit bull Terrior Both dam and sire are kissing lover dogs with not a mean bone anywhere in their body ,but both have super extraordinary strength solid as rocks and can easily gnaw through a hard soup bone in seconds just think of what they could do to a human arm or leg

  10. Emmanuel Mosaku

    Nice article

  11. Kelly Cook

    Hello my name is kelly my female chihuahua this is her second heat I would like to know how many puppys she is haveing she was bread in November of this year

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