Tolerance to 1,25 dihydroxyvitamin D₃ glycosides from Solanum glaucophyllum by the growing pig

Solanum glaucophyllum leaves contain high levels of glycosidically bound 1,25 dihydroxyvitamin D₃, the most important vitamin D metabolite. The tolerance to this source was evaluated during six weeks with fifty weaned pigs fed increasing levels (0, 2.5, 5, 10 and 20μg 1,25(OH)₂D₃/kg diet). The diet contained, per kg, 9.7g Ca, 3.5g digestible P and 2000IU cholecalciferol. Ten additional pigs were fed a diet containing 1000IU cholecalciferol/kg, without 1,25(OH)₂D₃. Weekly plasma and final kidney, bone and urinary mineral contents, bone density and breaking strength served as indicators for possible adverse effects of the supplement. All animals grew well and remained clinically healthy. The measured parameters remained unchanged when 1000 replaced 2000IU cholecalciferol/kg and when 1,25(OH)₂D₃ was fed up to 10μg/kg. Twenty μg 1,25(OH)₂D₃ increased plasma Ca and decreased plasma P from the 2^nd and the 4^th experimental week onwards, respectively. Twenty μg 1,25(OH)₂D₃ increased final plasma Ca and 1,25(OH)₂D₃ and reduced final plasma P by respectively 19, 56 and 13%. Twenty μg 1,25(OH)₂D₃ also increased kidney Ca and urinary Ca by 43 and 69%, respectively, reduced bone breaking strength by 12% and tended to decrease bone ash by 3%. To conclude, 2000IU D₃ was not beneficial compared to 1000IU cholecalciferol; up to 10μg 1,25(OH)₂D₃ per kg diet did not lead to observed adverse effects; 20μg 1,25(OH)₂D₃ altered the homeostatic regulation of Ca and P thus, may lead to first signs of possible adverse effects, such as soft tissue calcification.