Exploiting plant diversity and phenology for livestock health under climate change

Climate change presents serious challenges to livestock grazing systems, both for mitigation and adaptation. Legislative and consumer concerns increasingly prioritise environmental impacts. Simultaneously, climate warming favours increased disease threats just as antimicrobial resistance threatens the effectiveness of chemical control [1]. More diverse utilisation of plant resources has the potential to address several of these challenges: for example, deep-rooted plants such as shrubs and trees increase carbon sequestration, reduce water and nutrient run-off from extreme rainfall events, and provide nutritious fodder with proven antiparasitic effects, reducing reliance on chemical de-wormers [2,3]. Benefits are insufficiently realised because they are poorly characterised for mainstream livestock systems in the UK, compared with silvo-pastoral systems in warmer regions. Further, although integrating trees into grass-based systems confers resilience and ecological benefits, production efficiency could decrease in the short term, inhibiting uptake.

This project addresses the hypothesis that aligning plant phenology with seasonal parasite risks can enhance the effectiveness of tree-based solutions to disease threats, and hence their economic value. The objectives are organised around three distinct but complementary ecosystem services from trees on farmland, focusing on parasite control

Plant phenology as an indicator of parasite risk. Because plants use climatic cues to trigger seasonal events (=phenology), such events might predict risk periods for parasite infection. The spring scour worm Nematodirus battus emerges in response to rising soil temperature, and again in autumn when soil temperature falls to within a defined range [4]. Annual data on dates of leaf burst, flowering and leaf fall for UK tree and woodland/hedgerow plant species will be extracted from Nature's Calendar (UK Phenology Network) and compared with records of N. battus outbreaks from the VIDA veterinary laboratory database [5]. Results will test the hypothesis that spring and autumn events in particular plants can predict disease risk in a given year and location, and support treatment decisions by farmers.

Tree fodder as a targeted nutritional resource. Tanniferous tree leaves attenuate parasite impacts by reducing establishment and survival in the gut, by protecting protein from rumen degradation and consequently correcting protein loss in parasitized animals, and by dietary displacement of more highly contaminated lower-growing plants such as grasses [3]. Used alone over sustained periods, however, their nutritional value is often low, and excessively high tannin concentrations reduce feed intake and digestion. Tannin concentration and chemical structure will be analysed for ash, apple and willow leaves, during growth and after leaf-fall or drying, with chemical composition, available protein-energy content, and in-vitro antiparasitic efficacy. Results will calibrate feed basket formulation for targeted tree fodder supplementation at key times of parasite risk (e.g. summer coppice or pollard for early season parasite suppression; fallen leaves for removal of late-season drug-resistant worms). Selected mixes will be evaluated for digestibility and emissions in rumen simulators, and for palatability in feeding trials. Transmission models [7] will evaluate consequences of targeted seasonal intervention for parasite epidemiology and selection of drug resistance.

Modification of parasite transmission in treescapes. Trees improve drainage and soil structure, potentially reducing parasite transmission; while shading and animal aggregation can increase parasite availability [6]. Net effects could be complex [7], and affect how best to plan and utilise trees on pasture. This component will measure parasites and their environmental correlates (nematode larval density around translocated dung; summer soil saturation for liver fluke