Melatonin Sources in Sheep Rumen and Its Role in Reproductive Physiology

Area of Science:

• Animal Physiology
• Endocrinology
• Gastroenterology

Background:

• Mammalian gastrointestinal melatonin (Mel) levels are significantly higher than in the pineal gland.
• The precise origin and function of gastrointestinal Mel, particularly in reproductive regulation, remain largely unknown.

Purpose of the Study:

• To investigate the sources of high melatonin concentrations in the rumen (feed, microorganisms, rumen wall).
• To determine the biological effects of gastrointestinal melatonin on reproductive hormone regulation.

Main Methods:

• Analysis of melatonin in feed, rumen fluid, and blood.
• Correlation analysis between melatonin and specific rumen microbial populations.
• In vitro synthesis experiments and analysis of key melatonin synthesis enzymes and receptors in the rumen wall.
• Measurement of reproductive hormones (GnRH, LH, FSH, P4, E2) in blood post-feeding.

Main Results:

• Feed was identified as the primary source of high rumen melatonin.
• Rumen microorganisms showed a strong correlation with melatonin levels.
• The rumen wall possesses the necessary components for melatonin synthesis.
• Melatonin levels in rumen fluid and blood peaked two hours after feeding.
• Feeding altered reproductive hormone levels, with correlations observed between melatonin and GnRH, LH, progesterone, and estradiol.

Conclusions:

• Dietary intake is the principal driver of elevated rumen melatonin levels.
• Melatonin influences the fluctuations of key reproductive hormones, offering insights into food-based reproductive regulation.