The biological functions of copper in ruminant animals with emphasis on its influence on the rumen microbiota: A narrative review

Trace elements play a significant role in the health, metabolism, and productivity of ruminants. Copper(Cu) is an essential mineral required for various biological functions in ruminant animals. The dietary requirements and the maximum tolerable concentration for Cu in ruminants are subject to variation based on multiple factors such as animal breed, production type, Cu source, and the concurrent presence of antagonistic minerals. The role of Cu within the rumen microbial ecosystem is of considerable importance in ruminant species. The source and concentration of Cu can modulate the population dynamics and metabolic activities of rumen microorganisms, particularly bacteria and protozoa. Additionally, the resulting alterations in microbial metabolite production and feed digestibility can ultimately influence ruminant production. Organic and inorganic sources of Cu have distinct effects on rumen microorganisms. An optimal Cu amount is advantageous for rumen fermentation. Conversely, elevated Cu levels, particularly those derived from inorganic sources such as oxides and sulfates, can adversely affect feed digestibility, while hydroxychloride formulations and organic amino acid chelates have lower negative impacts on this parameter at high concentrations. Primary effects of Cu on rumen microbiota include alterations in bacterial populations, particularly an increase in fiber-degrading bacteria, a decrease in protozoan communities at elevated levels of Cu, changes in the production and composition of volatile fatty acids, and the potential reduction of methane emissions. This review discusses the biological effects of Cu in ruminants, encompassing Cu requirements, deficiency manifestations, and toxicity concerns, while emphasizing the interactions between Cu and rumen microbial populations and their metabolism.