While you can't completely control how many puppies your dog produces, there are some strategies you can use to boost the potential for a big litter. A variety of factors play a role in canine litter size.
Use a larger breed. Larger breeds tend to produce larger litters. In a study performed by the American Kennel Club in which more than 700,000 canine litters were evaluated to determine average litter sizes in large and small breeds, they found that Labrador retrievers, for example, averaged 7.6 pups in each litter. Yorkshire terriers, on the other hand, only averaged 3.3 pups in each litter.
Experience & Age
Use a female that has already had one litter but no more than four or five litters. After her first litter, a female generally produces larger litters each year through the third and maybe fourth litter. It will be an aberration for her to have large litters after the fifth litter. Also, the age at which a female has her first litter has some bearing on litter size. If a female does not have her first litter until four years of age, for example, she will likely not produce litters as large as a younger female would.
Nutrition (See References 1)
You do not want the female to bee too thin or fat when trying to breed for a large litter size. During the female's estrous cycle and first six weeks of pregnancy, the quantity and quality of the protein she receives is vital. The protein should be primarily animal-based rather than vegetable-based. Some of the important nutrients that a female should receive are vitamins A,C, and E as well as folic acid, amino acids such as taurine, minerals such as copper and zinc, and antioxidants such as lutein. During the last three weeks of pregnancy, you should feed the female anywhere from two to three times the normal quantities of nutrient-rich foods she normally eats.
Use a male that is no more than six years of age. Age affects the quality of semen that the male produces. If the quality of the sperm is low, the sperm may not fertilise enough ova to produce large litter sizes. The more ova that the sperm can fertilise the better the chances are of having a large litter size even if all of the ova are not fertilised.
Keep inbreeding to a minimum. Too much inbreeding can hamper a female's ability to produce many offspring. Also, if a particular line in a breed has poor reproductive genes and you continually breed them together, it will be difficult to produce large litter sizes in a line that has a genetic predisposition to produce small litter sizes.
Know precisely when ovulation is occurring in the female. Timing the mating is crucial to increasing litter size. The number of pups born will never exceed the number of ova, or eggs, that the female produces