Introduction: The mammalian liver is a functional and morphological complex organ with common histological features across different species. The mild variations in the mammalian liver were attributed to speciesadaptational changes, dietary habit, specific metabolic activities, and phylogenic organizational peculiarities.The previous studies on mammalian liver were not based on the macromolecules of the liver and could not provide detailed histological associations between herbivores, carnivores and omnivores of mammalian class. This study aimed to provide detailed histological association between the livers of six mammalian species.

Methodology: Ethical approval for this study was obtained from the Research and Bioethics Committee, Faculty of Basic Medical Sciences, Delta State University, Abraka (RBC/FBMS/DELSU/18/26). Six animals of mammalian species were utilized for this study in line with the guidelines for the care and use of animals for research.

Observations: A common trend was observed in the histological features of the liver across the six mammalian species studied: common histo-architectural features, distribution of glycoprotein, glycolipid and collagen type III were observed in the liver across the six mammalian species. Intermittent distribution of glycogen was observed in the liver of cow and high presence of glycogen was also observed in dog liver on oppose to their dietary classification.

Conclusion: This research work has established a strong histological association in the liver of three groups of mammals, based on their diet. The work has been able to provide histochemical evidence of the existence of a near phylogenetic relationship between the six species of mammals, studied.

Keywords: Mammal; Liver; Histoachitectural; Adaptation; Histology, Phylogeny