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The study was undertaken to find out the effects of over supplementation of dietary calcium and vitamin D3 on the mineralization of growing skeleton, taking rabbit as an animal model; further to study the effects of Nandrolone deconoate and TGF-beta1 on the mineralization of osteopenic bones. Twenty four New Zealand White rabbits of either sex, 60 day old, were randomly divided in 4 equal groups, A, B, C and D. The animals of groups B, C and D were administered with oral supplementation of calcium (2000 mg/kg of standard rabbit feed) and vit-D3 (1000 IU/kg of standard feed) for 60 days. The animals of group A were given standard ration without any supplementation. After 60 days, the Ca-vit.D3 supplementation was discontinued; and the animals of group C were administered with TGF-beta1 (10 ng, i.m.) once in every three days and animals of group D were given Nandrolone deconoate (10 mg, i.m.) once every week for 30 days, whereas in animals of group B, no treatment was given. All the animals were evaluated based on different observations like body weight, radiographic observations, circulating biochemical and hormone profile (plasma Ca, IP, AP, OC and iPTH) every 15 days up to 60 days after initiation of treatment. The results indicated that the body weight of rabbits in different groups increased gradually and steadily at different intervals till the end of observation period, however, the increase was non-significantly more in group D. The CI in group A increased gradually at different intervals; whereas in groups B, C and D, there was no appreciable increase in the CI during the period of Ca-vit.D3 supplementation, suggesting development of osteopenia. Treatment with TGF-beta1 did not increase the CI significantly, whereas Nandrolone treatment resulted in significant increase in the CI on days 45 and 60. The plasma Ca levels showed slight but gradual increase from day 0 to 60 in almost all groups. Subsequently also, there was no marked change at different intervals in groups A and B; however, significant reduction in plasma Ca was noticed in group C on 15(th) day and in group D on 60(th) day after initiation of treatment. Plasma IP levels in groups B and C showed a decreasing trend up to day 60. After discontinuation of Ca-vit.D3 supplementation, in group B, it further decreased to remain significantly lower on 15(th) day, and in groups C and D, it increased significantly on 60(th) post-treatment day. There was no significant change in the AP activity during the entire period of study in group A; whereas significant reduction in AP activity was measured on 30(th) and 60(th) days of treatment in groups B and C, and on 15(th) day of treatment in group D. Plasma iPTH values did not show any significant change at any interval during the first 60 days in all groups. On 30(th) and 60(th) days of treatment, the mean iPTH level remained significantly lesser in group B. In all groups treated with over supplementation of Ca and vit.D3, there was a non-significant increase in the plasma OC levels up to day 60; however, there was no significant difference between the groups. It can be concluded that additional supplementation of Ca and vit.D3 results in osteopenia in growing rabbits. Administration of Nandrolone helps to increase the mineral density in osteopenic bones, whereas TGF-beta1 does not seem to have positive effect on the skeletal mineralization.

Survey radiographs of all the growing dogs aged up to 6 months, which were presented to the IVRI polyclinics during the 10 year period were screened to study the determinants of bone mass, density and growth. On the basis of clinical history and radiographic evaluation of long bones, the cases were categorizes as normal or osteopenic. The relative cortical density (RCD), cortical index (CI), diameter of bone at the distal metaphysis (DDFM) and the width of the growth plate (WFGP) were determined by taking the femur as a model bone in German shepherd, Doberman and Spitz breeds of dogs at different age groups. The results showed that RCD was the least in 0-2 month old normal growing dogs in all the breeds. As the age advanced up to 6 months the RCD increased 20-25% and at 6 months, Spitz and Doberman showed significant increase (P<0.05) in the RCD. In osteopenic bones, RCD remained less (25-50%) than that of normal animals at all age groups, and at 2-6 months of age, RCD in osteopenic bones was significantly lesser than in normal animals in GSD and Spitz breeds. The CI was also the least at 0-2 months of age in normal dogs. The CI increased about 50% at 4-6 months of age in GSD and Spitz. Whereas in Dob., there was no appreciable change in the CI at different age groups, and at 2-6 months it was significantly (P<0.05) lesser than that of Spitz. In osteopenic bones, the CI was 25-75% lesser than that of normal animals at different age groups, and at 4-6 months there was significant difference (P<0.05) between the normal and osteopenic bones in GSD and Spitz. The DDFM was the least in 0-2 month old normal growing dogs, and as the age advanced, it increased 10-20% up to 6 months. However, no significant difference in the DDFM was seen between breeds and also between the normal and osteopenic bones at different age groups. In normal animals, the WFGP was the highest in the early age, subsequently it reduced 50-75% and at the 4-6 months there was a significant decrease (P<0.05) in all breeds of dogs. And at the 4-6 months, there was significant (P<0.05) difference in the WFGP between breeds, it was the least in Spitz and maximum in Dob., suggesting faster growth plate closure in Spitz than in GSD and Dob. breeds. In osteopenic bones, WFGP was generally more than in normal animals, and at 4-6 months (about 3-5 times more) there was significant difference (p<0.05) between the normal and osteopenic bones in all breeds, indicating that physeal closure may be delayed in osteopenic bones. The results indicate that among different breeds Doberman breed has the least bone mass and may be more prone to osteopenia; whereas Spitz has the strongest bone.