Equine atypical myopathy: consumption of sycamore maple seedlings () by pastured horses is driven by seedling maturity and might be associated with phenolic compounds.

Abstract

BACKGROUND: Poisoning withL. in horses contradicts the hypothesis of coexistence between plants and vertebrate herbivores being mediated through antipastoral traits as toxins. However, incidental observations showed that horses evadedseedlings with primary leaves. The objective of the present cross-discipline study was (i) to analyse whether developmental stages ofL. differed as to phenolics hypothesised as antipastoral traits, and (ii) to observe systematically the selection behaviour of pastured horses towardsseedlings. METHODS: Phenolic profiles of five developmental stages from fruits to seedlings of progressing age up to adult leaves ofandL. were characterised. Video recordings of grazing behaviour of 29 pastured horses towards seedlings ofresulted into 117 sequences as additional field data. RESULTS: The horses ingested 19.1 per cent of juvenile seedlings with cotyledons (1.65 mg total phenolics/g fresh weight (FW), 82 compounds, 0.02 mg total gallic acid/g FW) yet only 5.46 per cent of older seedlings with primary leaves (8.48 mg total phenolics/g FW, 120 compounds, 3.13 mg total gallic acid/g FW). CONCLUSION: Horses distinguished between seedlings in distinct stages that could be chemically distinguished, too.seedlings with primary leaves provide a strong, but not complete antipastoral effect that correlates with dramatic changes in phenolic compounds.