Temporal endocrine and hematological consequences of biological extremes in porcine birth weight

To characterize the potential long-term impact of intrauterine growth restriction (IUGR), we assessed the endocrine and hematological consequences of IUGR at birth and in the early postnatal period. Piglets (n = 911) were collected pre-suckling, weighed, and blood sampled, with rectal temperatures assessed two hours later, and sampling repeated at 20 days of age (D20). A subset of piglets was classified as IUGR (n = 92) or large for gestational age (LGA; n = 92) based on birthweight. At birth, IUGR piglets had decreased T3 and T4 relative to LGA, which may be associated with concomitantly decreased rectal temperatures. T4 had normalized by D20, while T3 was increased in IUGR relative to LGA at this timepoint. Cortisol did not differ between groups at either timepoint. IUGR piglets also experienced decreased hematocrit, blood glucose, and plasma protein at birth, while only plasma protein remained decreased at D20. At birth, male IUGR piglets had decreased testosterone compared to LGA piglets, while estradiol levels were not altered in female IUGR piglets. While IUGR piglets exhibited catch-up growth, they failed to reach an appropriate weight by D20. These results suggest that some of the systemic dysregulations occurring in IUGR piglets have normalized by D20, even though bodyweight fails to recover.