Interpretive Summary: Melatonin alters bovine uterine artery hemodynamics, vaginal temperatures, and fetal morphometrics during late gestational nutrient restriction in a season-dependent manner

By Anne Zinn

External factors, such as maternal plane of nutrition and ambient temperature during gestation, are critical determinants of fetal development and postnatal outcomes. Research recently published in the Journal of Animal Science aimed to use beef heifers to evaluate the effect of maternal nutrient restriction and melatonin supplementation during late gestation on uteroplacental blood flow, vaginal temperatures, and fetal morphometrics during compromised pregnancy. It was hypothesized that maternal nutrient restriction during late gestation would decrease uteroplacental blood flow and melatonin supplementation during the daytime, which would mitigate the adverse effects of compromised pregnancy. Additionally, it was thought that vaginal temperatures would display a circadian rhythm, increasing from morning to afternoon, but that melatonin supplementation would prevent this increase in the afternoon due to its hypothermic effects and that nutrient restriction would reduce fetal weights and impair organ morphometrics, whereas melatonin supplementation would negate these effects.

Results indicated that nutrient restriction during the fall, when animals are exposed to cold weather, appeared to be more detrimental to the dam uteroplacental blood flow. Additionally, results demonstrated that dietary melatonin appeared to decrease vaginal temperatures and rescue fetal weights when supplemented in the summer as compared with the fall. 

The hypothermic effects of melatonin during the summer are promising. Future research should consider dietary melatonin supplementation during heat stress exposure and should evaluate epigenetic modifications or gene expression alterations in fetal organs from dams that were supplemented with melatonin.

The full paper can be found on the Journal of Animal Science webpage.