Exploiting plant phenology and diversity for livestock health under climate change

This covers field studies directly measuring the effect of trees on the microclimate, likely consequences for parasites and vectors, directly and via effects on livestock and other ecosystem components. The review also collates the limited empirical evidence for effects of trees on parasite loads in livestock, identifies knowledge gaps, and assesses how modelling can be used to predict such effects.<br><br>Chapters 2 and 3 are field studies assessing the impact of agroforestry on gastrointestinal nematodes of sheep.

Chapter 2 is a comparative study between sheep kept on open pastures and in ash agroforestry fields to determine whether agroforestry systems are a potential method of integrating trees onto farms without negative impacts on parasite control. This study involved field collections of faeces and pasture samples throughout the grazing season to determine any differences in seasonal patterns of infection, and post-mortem collection of gastrointestinal tracts and the extraction and identification of adult nematodes.

Chapter 3 used only the agroforestry fields to assess the impact of trees at a finer scale. Each field was divided into 8-9 segments with different levels of tree cover to assess spatial differences in parasite abundance. GPS collars tracked movement around the field to see how this related to microclimate differences in different areas.

Rectal faecal samples allowed assessment of relationships between the movement patterns of individual sheep and parasite burden.<br><br>Chapters 4, 5 and 6 pertain to the feeding of tree fodder. Chapter 4 uses published data to assess the nutraceutical potential of a range of tree species found in the UK and Ireland, covering their palatability, nutritional content, secondary metabolite content and data on anthelmintic activity.

Chapter 5 then takes five of these species which show good potential as livestock fodder and assesses the seasonal and interannual variation in the tannin content of the leaves. Chapter 6 is a modelling study which uses data from Chapter 4 on the anthelmintic properties of tree leaves to assess the impact of feeding these at different times of the year on gastrointestinal nematode transmission, and optimal intervention strategies.<br><br>Chapter 7 discusses how the thesis advances understanding of how trees on pasture can affect parasite transmission, by integrating insights from the chapters using empirical and modelling approaches and extending to wider contexts.

It considers how results can be applied to guide policy and practice as trees are increasingly used on grazing land to mitigate and adapt to climate change and identifies priorities for future research.<br>