Proximal intestinal absorption of calcium is elevated in proportion to growth rate but not bone mass is small for gestational age piglets

During the first year of life, body calcium content increases faster in relation to body size than any other time during growth. Studies have shown postnatal growth and bone mineralization differences between appropriate for gestational age and small for gestational age infants. The objective of this study was to compare duodenal calcium transport using intestinal ligated loop technique in 21-day-old small for gestational age (birth weight of <1.2 kg) and appropriate for gestational age piglets (birth weight of ≥1.4 kg). Piglets were fed liquid formula between day 5 and 21 of life and monitored daily for weight gain. At day 21 calcium absorption was measured followed by measurement of bone mass using dual energy x-ray absorptiometry. Small for gestational age piglets had greater calcium absorption and growth rate than appropriate for gestational age piglets. Birth weight was negatively related to weight gain and calcium absorption. Weight gain was positively related to calcium absorption. Appropriate for gestational age piglets had significantly higher whole body bone mineral content than small for gestational age piglets even after correction for body size. Whole body bone mineral content was positively correlated with birth weight and negatively correlated with calcium absorption. These observations suggest that small for gestational age piglets are capable of absorbing elevated amounts of calcium in the proximal intestine in support of compensatory growth. However, at 21 days of age small for gestational age piglets are similar in size but have lower bone mass compared to appropriate for gestational age piglets.