Manipulation of the ruminant gastrointestinal tract microbiomes for reduced environmental impact of nitrogen excretion from dairy cows

Functional genes related to amino acid biosynthesis and propionate metabolism were enriched in HE cows, while methanogenesis pathways were enriched in LE cows. Chapter 3 further developed this work by assessing the effect of RSM-based diets with different CP levels (140, 155, and 170 g/kg DM; R140, R155 and R170, respectively) and the inclusion of a conventional concentrate containing both SBM and RSM (155 g/kg DM; C155) on cow performance and the rumen microbiome.

Dietary CP level and protein sources influenced production traits, the rumen microbial composition and functions. In chapter 4, an in vitro rumen fermentation approach was used to investigate the effects of substituting SBM and RSM with three microalgae species—Spirulina platensis (SP), Chlorella vulgaris (CLV), and Nannochloropsis gaditana (NG)—at 5%, 10%, and 20% inclusion levels. Microalgae inclusion had minimal effects on fermentation parameters, except CLV at 10 and 20%, which significantly reduced CH4 concentration. <br><br><i>Thesis is embargoed until 31 July 2029.</i><br>