PSXIII-B-19 - The Effect of Maternal Melatonin Supplementation During Mid to Late Gestation on Fetal Piglet Hepatic Gene Expression

Abstract: Using melatonin as a gestational therapeutic due to its antioxidant and vasodilative properties increases fetal morphometric measurements in ruminant models, however its effects on gestating swine and fetal circadian regulation remain unknown. This study evaluated the effects of dietary melatonin supplementation during gestation on fetal hepatic circadian regulatory and metabolic gene expression. Twenty-four pregnant sows were randomly assigned to either melatonin (20mg/d; MEL) or control (CON) and 0500h (AM) or 1700h (PM) harvest timepoint across fall and spring replicates. The fall replicate occurred from gestational day 38±1 to 99±1, while spring was days 41 to 106±1. At harvest small, medium, and large piglets were identified by body weight and their livers were collected. Data were analyzed using a linear mixed model by the MIXED procedure of SAS. Cry1 expression tended to increase (P=0.0575) in large fetuses compared to small during the fall, while large fetuses had the greatest expression, medium intermediary, and small least during the spring (P=0.0056). Cry2 was reduced (P< 0.001) in MEL offspring compared to CON in the fall. There was a Treatment × Class interaction (P=0.0104) for Cry2 expression during spring wherein, CON-AM was reduced compared to CON-PM, however no differences between MEL groups. A Treatment × Class interaction (P=0.0511) of Per2 expression was present in the fall, where expression of small control fetuses was reduced compared to remaining controls. Spring Per2 expression increased (P=0.0122) in large fetuses compared to other sizes, Per2 also increased (P=0.0039) in PM compared to AM. Fall IGF1 expression increased (P=0.0366) in large fetuses compared to medium and small, and spring IGF1 expression increased (P=0.0067) in large fetuses compared to small. These findings suggest that maternal melatonin supplementation during gestation modulates expression of hepatic circadian regulatory and metabolic genes which may impact growth and developmental efficiency postnatally in a seasonal manner.