This research was performed to evaluate the utility of several serum and urine parameters as well as
bone ash and plasma
parathormone assay to diagnose and monitor diet-related
osteopenia in growing pigs. Five diets were tested as follows:
calcium-deficient,
phosphorus-replete; moderate-deficiency of
calcium and
phosphorus; marked deficiency of
calcium and
phosphorus;
calcium replete,
phosphorus deficient; and
vitamin D deficient. Parameters monitored included serum
calcium and
phosphorus as well as ratios of urine
calcium to
creatinine,
phosphorus to
creatinine,
calcium to
phosphorus, and percent fractional excretions of
calcium and
phosphorus. Plasma
parathormone (PTH) levels were monitored in 2 of 3 experiments. Osteopenic bone differences at necropsy were evaluated by bone density, percent ash, ash per milliliter bone,
calcium per milliliter bone, and
phosphorus per milliliter bone. Marked change in urine
mineral parameters, especially the
calcium-to-
phosphorus 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 monitored, plasma PTH levels were elevated following treatment, which confirms the hyperparathyroid state induced by the test diets. Significant differences in bone mineralization between control and treatment diets at necropsy were generally observed. The results of this study indicate that the analysis 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 described. Several urine
mineral reference intervals for application to field investigations are included. Research into application of similar techniques to evaluate
calcium and
phosphorus homeostasis in pigs of all ages, including gestating and lactating gilts and sows, appears warranted.