The future of the Neapolitan Mastiff, as every other animal population, depends on the surviving and reproductive ability of every single specimen of the breed.
A certain part of these traits have a genetic component, but their expression depends on genotype, environment and genotype/environment interaction.
In other words we can say that some genotypes have a better environmental adaptation and they are more efficient in surviving and generating offspring. Today progress in veterinary medicine and the use of advanced reproductive techniques allow some specimens to live and reproduce which, only a few years ago, would not have survived. This is an important aspect to take into consideration in the selection of such a particular breed as the Neapolitan Mastiff.
The Neapolitan Mastiff is an ancient breed selected over centuries by breeders with very precise objectives attempting to fix some particular traits described in the breed standard.
The breeders selected to breed from individuals they considered carried those traits regarded as important for the morphological aspect of the breed. But human s=election interacts with natural selection that favors those individuals that have best adapted over the centuries and are therefore closest to the species (not breed) fitness. Artificial and natural selection frequently have different objectives and act in different ways as quite often human selective choices concern particular traits (extreme type) far from Canis familiaris species characteristics.
The Neapolitan Mastiff is surely very far from the normo-type traits of its species so the artificial selection applied by breeders must be strong and consistent.
It is not easy to individuate the normo-type characteristics of Canis Familiaris but we can say that Neapolitan Mastiffs are far removed from it. On the other hand, people who love this breed, love these extreme qualities and very often the more these breed traits are extreme the more the individuals is appreciated.
Natural selection applies different strategies to the benefit of the best adapted individuals taking them back to the species standard: fertility traits and longevity decrease, immunological responses decrease, disease susceptibility increase, toxic substance resistance and mortality increases. All these process are present, not only in the dog (where there are very few studies), but also in every domestic species.
In this situation breed data must be collected and verified. Data collection regarding dog breeding is very difficult because affective aspects of the human-dog relationship can sometimes cover up objectivity. Research can be conducted with owners, breeders, veterinarians or, as in the study, analyzing data registered in Stud Books (R.O.I.).

Demographic data, fertility and inbreeding:
The annual entries recorded in the Italian Kennel Club LOI and LIR studbooks were analyzed from 1974 to 2001 with a total number of 23202 dogs. The entire Italian pedigree population of Neapolitan Mastiffs was analyzed. In these registers all litters from private breeders, recognized affix breeders and imported dogs with FCI pedigrees are recorded. The Italian Kennel Club supplied the data used in this research. 1986 there is an increase, though not linear, in the number of dams compared to the number of sires, reaching a sex ration of 1.78 in 1994. Between 1996 and 1998 there is a negative trend in the number of dams (sex ration D/S < 1.50). In the last three years the ration is increasing.
The high values regarding the number of sires should correspond to a high genetic variability, a very important factor in the evolution of every population. Nevertheless average F value trend is slightly positive.
Graph. 15 shows the distribution of the number of sires (%) divided per year of age from 1974 to 1997. The trend perfectly reflects what was observed for dams showing the highest frequency (26.6%) for two-year-old dogs, decreasing to the 11.7% of five-year-old dogs. Dams and sires older than six years are very rare.
The number of litters per sire is analyzed in graph. 16. There is a clear relation to the dams’ situation: the majority of the stud dogs (>53%) produce only one litter in their life. The main difference with dams is the lower percentages: dams have 9 litters as the highest value, on the other hand, though a very small percentage, there are sires with more than 12 litters reaching a maximum of 34 litters.
Average F per year and maximum F per year (1977-2001) is shown in graph nº17. From 1977 to 1983 F values are quite low (<0.05). Between 1984 and 1992 they are comprised between 0.05 and 0.07; in 1994 F pass 0.008 and reach the maximum value in 1997 with F=0.094. In the last three years from 1999 to 2001 F is around 0.09.
Mean F values are clearly higher (0.09) compared to F values of other breeds like English Cocker Spaniel (0.05), English Springer Spaniel (0.04), and Boxer (0.03).
During this research maximum F values were calculated: the line indicating it shows alternate trends with an interesting increase in the last years to reach a peak of 0.571 signifying repeated inbreed mating. This trend can be observed in graph. 18 showing class division. Mean and maximum F values were analyzed in Kennels D, G, O, S, T, with a total production of 184, 134, 95, 74, 69; the results are alternating, but differ substantially from kennel to kennel.

Conclusions:
For the first time in Italy a statistical analysis of demographic and genetic parameters of the Neapolitan Mastiff breed has been conducted.  
Analyzed data consider the entire registered population. Entries are registered with the principle of bona fide on the part of the breeder of the litter, however considering the high amount of data analyzed, the effect of false registration should be considered null. As in every dog breed the majority of subjects will be house pets not utilized for breeding. Nevertheless a high percentage of dams produce only one litter and the same applies to more than 50% of sires. The average number of dams per sire is 1.5 and the maximum number of dams per sire is 34. Again sires and dams are usually young, so the genetic variability within the population is kept quite high.
The litter size parameter underlines that quite a high percentage of bitches have low fertility (12% one puppy, 14% two puppies).
The fertility trend in the different years is quite constant but it is decreasing in the last years. It is important to underline that fertility must be considered a representative parameter for breed fitness evaluation; this parameter should be precisely analyzed creating homogeneous clusters.
The inbreeding coefficient trend, quite high in comparison with other breeds and particularly peaking in some subjects, underlines the importance of paying more attention to the selection of specimens for mating.
While inbreeding allows the increase of selective pressure to fix various attributes, high homozygosis can produce undesirable traits and in particular a decrease in fertility (mainly in sires), higher disease susceptibility and higher mortality.
Now days it is easy to calculate the inbreeding coefficient using appropriate software.