Osteopenic disease in growing pigs: diagnostic methods using serum and urine calcium and phosphorus values, parathormone assay, and bone analysis

This research was performed to evaluate the utility of several serum and ur ine parameters as well as bone ash and plasma parathormone assay to diagnos e and monitor diet-related osteopenia in growing pigs. Five diets were test ed as follows: calcium-deficient, phosphorus-replete; moderate-deficiency o f calcium and phosphorus; marked deficiency of calcium and phosphorus; calc ium replete, phosphorus deficient; and vitamin D deficient. Parameters moni tored included serum calcium and phosphorus as well as ratios of urine calc ium to creatinine, phosphorus to creatinine, calcium to phosphorus, and per cent fractional excretions of calcium and phosphorus. Plasma parathormone ( PTH) levels were monitored in 2 of 3 experiments. Osteopenic bone differenc es at necropsy were evaluated by bone density, percent ash, ash per millili ter bone, calcium per milliliter bone, and phosphorus per milliliter bone. Marked change in urine mineral parameters, especially the calcium-to-phosph orus ratio, typically occurred within 1 to 2 days of treatment and preceded significant change in serum mineral or plasma PTH by 2 to 3 weeks. When mo nitored, plasma PTH levels were elevated following treatment, which confirm s the hyperparathyroid state induced by the test diets. Significant differe nces in bone mineralization between control and treatment diets at necropsy were generally observed. The results of this study indicate that the analy sis of urine minerals offers an early, noninvasive technique to investigate diet-associated osteopenic disease in growing pigs, which can be supported further by bone mineral analysis at postmortem using techniques herein des cribed. Several urine mineral reference intervals for application to held i nvestigations are included. Research into application of similar techniques to evaluate calcium and phosphorus homeostasis in pigs of all ages, includ ing gestating and lactating gilts and sows, appears warranted.