The potential applications of brown seaweed as an alternative feed for ruminant livestock

Abstract

This thesis builds on a growing area of scientific research aimed at addressing the feasibility and potential benefits of feeding brown seaweed to ruminant livestock. The primary objectives of this research were to: identify gaps in current knowledge on the potential use of brown seaweed as a feed source for ruminant livestock; to establish a baseline knowledge of the nutritional composition of four commonly found brown seaweed species in Northern Ireland; to investigate the use of infrared spectroscopy as a tool to rapidly measure the nutritional composition of brown seaweed and to explore the use of ensilage as a preservation method for the application of brown seaweed as a ruminant livestock feed.

Chapter 1 discusses a rationale for investigating alternative feeds for the ruminant livestock sector by discussing the current challenges to modern agriculture (e.g. climate change, rising feed costs and resource depletion) which accumulate in a series of unprecedented threats to the security of livestock feed supply chains. Following this, Chapter 2 presents a review of the current scientific literature on the use of seaweed in ruminant diets. The first experimental chapter (Chapter 3) describes season- and species-related trends in the nutritive value of a natural (i.e. uncultivated) population of seaweeds collected in Northern Ireland. Four species (Ascophyllum nodosum (L.) Le Jolis, Fucus vesiculosus Linnaeus, Laminaria digitata (Hudson) J.V. Lamouroux and Saccharina latissimi (L.) C.E. Lane, C. Mayes, Druehl & G.W. Saunders) were chosen based on their availability in Northern Atlantic regions. The chemical composition and in vitro dry matter digestibility of the species were screened over a 10-month period. Chapter 4 was designed to screen the effects of the four brown seaweed species on in vitro gas and methane production compared to Medicago sativa, a terrestrial forage. Chapter 5 discusses the potential of developing rapid methods of measuring the nutritive value of seaweeds in the ruminant diet using Near Infrared (NIR) and Mid Infrared (MIR) spectroscopy. Finally, Chapters 6 and 7 explored the effect of ensilage, a commonly used preservation method for ruminant livestock feeds, on the characteristics of brown seaweed as a livestock feed. In a preliminary study (Chapter 6), two species (Fucus vesiculosus and Saccharina latissimi) were selected for ensilage; these species were chosen based on their contrasting chemical profiles and their high biomass availability at the time of harvest. Saccharina latissimi progressed to the next study (Chapter 7) which was a more in-depth exploration of the characteristics of seaweed silage. The studies presented in Chapters 6 and 7 highlight the potential of ensilage as a method of preserving the nutritive value of Saccharina latissimi, which might represent a feasible, post-harvest method of preserving seaweeds in temperate regions such as Northern Ireland.

The body of work presented in this thesis contributes to the emerging knowledge on the potential applications of brown seaweed as a feed for ruminant livestock. It is expected that this work will support the continued search for viable, alternative feeds for livestock to safeguard local feed security and to promote the sustainability of the ruminant livestock sector in Northern Ireland.