This collection features five peer-reviewed reviews on dietary supplements in dairy cattle nutrition. The first chapter addresses the manipulation of rumen fermentation to maximise the efficiency of feed utilisation and increase ruminant productivity. It considers a wide variety of approaches, including the use of dietary buffers. The second chapter reviews the use of probiotics as supplements for ruminants to promote digestive efficiency and productivity. The chapter summarises the benefits and modes of action of probiotics, as well as their role in optimising feed efficiency and reducing methane production. The third chapter considers the beneficial roles of plant secondary compounds in sustainable ruminant nutrition. It describes the effects and composition of the three major groups of plant secondary compounds: essential oils, tannins and saponins. The fourth chapter discusses the growing need for alternative feed sources as a result of increasing demand for meat and dairy products. The chapter reviews the nutritional composition of seaweed and introduces it as a potential novel protein supplement in animal feeds. The final chapter evaluates the role of macroalgae as a potential anti-methanogenic ruminant feed resource and reviews its impact on animal production and performance.

Major advances in analytical techniques and genomics have transformed our understanding of rumen microbiology. This understanding is of critical importance to livestock production since rumen function affects nutritional efficiency, emissions from ruminants (such as methane and nitrous oxide) as well as animal health. This collection reviews what we know about rumen microbiota and the role of nutritional strategies in optimising their function for more sustainable livestock production. Part 1 summarises advances in methods for analysing the rumen microbiome. Part 2 reviews recent research on the role of different types of rumen microbiota such as bacteria, archaea, anaerobic fungi, viruses and the rumen wall microbial community. Part 3 discusses the way the rumen processes nutrients such as fibre and protein as well as outputs such as energy, lipids and methane emissions. Part 4 explores nutritional strategies to optimise rumen function, including the role of pasture, silage, cereal feed, plant secondary compounds and probiotics.