Viruses are the most abundant biological entity, yet the roles of viruses within ecosystems are poorly understood. Work from other environments demonstrates that bacteriophage populations contain auxiliary metabolism genes thought to increase host fitness by altering host metabolism. As an attempt to better understand the viral influence on host bacterial populations, we investigated viral and total microbial community structure and function using culture-independent metagenomic approaches under 4 different dietary conditions. Using a shared read approach based on median k-mer profiling, the structure of total microbial communities significantly differed based on diet and host, whereas enriched viral metagenomes differed only by diet. The majority of differences between viral populations from different diets were metabolic in nature. Using community level metabolic networks, we further explored why different diets enrich phage communities for specific metabolic pathways. Enzymes differentially abundant in the total metagenome and virome had significantly higher betweenness centrality and a lower average shortest path length compared with nondifferential genes in the network. In addition, differential viral genes had a significantly higher total degree and in-degree compared with nondifferential genes. This ongoing work begins to suggest that diet, rather than host factors, has a stronger influence on the structuring of rumen phage populations and that phages encode for an adaptive repository of central metabolic functions related to selection pressures driven by altering environmental conditions. Current efforts are focused on better understanding what governs why certain central metabolic genes are enriched and how this is related to the flow of information through metabolic networks.