Accumulation of melanin in the peritoneum causes black abdomens in broilers

A suspected case of localized visceral hyperpigmentation was described for a breed of broiler in China. Using optical microscopy, the accumulation of pigments in the abdominal skin and visceral peritoneum was observed. Electron microscopy was used to further study the ultrastructure of the pigmented peritoneum, and pigment granules resembling melanosomes at different stages were found, and melanocytes were present in this tissue. Infrared spectroscopy was used to analyze the physical-chemical properties of pigments extracted from these broilers. Using synthetic melanin as a reference and the melanin from the peritoneum of Silkie fowls as a control, the pigments in the peritonea of these broilers were found to be melanin, and it had a chemical structure similar to that of melanin from the Silkie fowl peritoneum. In this way, the black abdomens of these broilers were found to have been caused by accumulation of melanin produced by melanocytes in visceral peritonea.