APPEARANCE OF OSSIFICATION CENTERS OF THE LIMBS AND SKELETAL DEVELOPMENT IN NEWBORN TOY-DOG BREEDS: RADIOGRAPHIC, MORPHOMETRIC AND HISTOLOGICAL ANALYSIS

The study aims to find out the chronological appearance of the ossification centers of appendicular skeleton of newborn toy-breed dogs during the first month of life and to correlate the data obtained with morphometric measures of the skeleton by radiological and anatomical approach. Data obtained were implemented with bone mineral density (BMD) analysis of the long bones and histological and histochemical analysis of limbs bone sections, to evaluate and quantify the trends of the ossification process and the architectural changes of ossification centers. The study was carried out in 37 newborn toy-breed dogs <28 days old, spontaneously died for unrelated reasons with this study, divided into 4 groups on the basis of age (first week, second week, third week and fourth week). The forelimbs and the hind limbs have been evaluated by radiological and histological analysis. Long bones, cranial and body measurements, both radiological and anatomical, were taken and the BMD of radius and ulna and of os femoris was calculated. The results have been correlated through statistical analysis and compared with standard charts proposed by Literature in order to assess significant differences with medium and large breed dogs. The appearance of most of the ossification centers reflects the timing of ossification of medium and large breed dogs, however the behavior of some ossification centers changes and therefore might be considered typical of toy-dog breeds. Femoral length could be taken into consideration as a parameter to assess the developmental rate and the age of toy-breed dogs during the growing period, particularly in the first 4 weeks of age. Increasing BMD is highly correlated with increasing long bones length and seems to confirm the space-time relationship between BMD in canine newborn skeleton and in long bones growth. The radiological, histological and bone mineral density analysis and the correlations between long-bones length, skull diameters, age and body mass, might be currently appropriate to determine the skeletal age in newborn toy-dog breeds.