What Influences a Puppy Litter Size?

influence the size of a litter of puppies

Deciding on the size of a puppy litter is difficult and relies on so many different factors, including serendipity. Despite what you might have read, you will never know exactly how many puppies a female will carry before she actually is pregnant and checked.

Scientifically, there is no such thing as “a fertile bitch” even if empirically, 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 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:

  • Pomeranians average between 1 to 4 pups a litter.
  • Border Terriers average between 2 to 8 pups a litter.
  • Boxers average between 5 to 8 pups a litter.
  • Bullmastiffs average between 5 to 13 pups a litter.

Nature is generally well made 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 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 of such ranges. Let’s say for your breed the average litter size is between 8 and 12, some breeders want to help their Dam get to 11, 12 or even 13.

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 factor in the size of a puppy litter is the influence of a high coefficient of inbreeding for this particular litter.

The Institute of Canine Biology published a chart illustrating 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 most inbred the puppies are, the smallest 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 a litter size. Generally, it is known that the smaller the breed the smaller the litter size and same goes for larger breeds, larger the breed larger the litter.

For example, spaniels and retrievers usually have anywhere from 4 to 8 puppies at a time while on the other hand, smaller dogs such as a terrier 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. 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 will have a smaller litter size. 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 of third heat.

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 will decrease. Larger litters will most likely occur when the male dog is under 5 years of age as it is easier and better for the sperm to enter the female’s eggs.

This is why most famous champions and dogs are used extremely often and intensively in order to impregnate as many quality Dams as possible.

Health of the Dam

Health plays a vital role in a litter. In clear, 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 get smaller puppy counts. 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 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 enough reassurance 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 was give 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.

The study findings were that supplementing top quality formulated dog food along with rations of cottage cheese and meat often increased the size of the litter.

Size of the Gene Pool

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

Many traits have high heritability and fertility is definitely not one of them. The heritability is about 10-15% that means that one cannot rely on genes for increasing the size of the litter.

On the other hand, common examples of inherited traits in dogs are:

  • 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 biologic or physiologic mechanisms that increased the puppy count.

Things such as diet, breed type and health of both the mother and father of course 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 has 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 a 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 for the dam or stud, the first two litter will often be smaller than the following ones.

Bottomline, 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 wide, but nothing is sure.

Read more quality articles about dog breeding!

6 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. 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!

  2. 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. 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.

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