[lisatodd]

this was written by Dr. Carmen L. Battaglia.....i only copied part of the article.


Most of the small breeds, notably the toys and terriers usually produce very small litters. This is in part because of their very small size, which limits their capacity to carry large litters. But in the larger breeds there are wide variations in litter size ranging from 1 to 21 and in a some instances they have been larger. Breeders have for years unsuccessfully tired to make improvements in litter size via breeding and selection techniques with little success. While many traits have high heritability, litter size is not one of them. It has a low heritability, around 10 -15 % which means that one can not count on the genes to increase the number of pups born. What can be expected will largely be determined by the non-additive factors of dominance. For example, wither height has a heritability estimate of 40-65%, which is reasonably high. Therefore, it is relatively easy for the breeders of the German Shepherd Dog to produce offspring with high withers. However, when it comes to litter size selecting parents who come from large litters will not improve the number of pups born. However, the physical condition of the dam at the time she is bred however has been shown to increase or decrease litter size. For example, obese bitches tend to have smaller litters than those that are fit and trim. Nutrition is still another factor that was suspected to affect litter size. Some thought it would vary between and within breeds. The fact that there are large variations in litter size attracted the attention