Relationship of Indole Alkaloids to Palatability of Phalaris arundinacea L.1

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Abstract
We screened 411 diverse genotypes of reed canarygrass (Phalaris arundinacea L.)for palatability to sheep. Indole alkaloid type and concentration were estimated in selected plants by either the xanthydrol method or by total base titration; the methods were highly correlated (r = +0.94).Either gramine or 5‐methoxy‐N,N‐dimethyltryptamine (5‐MeO‐DMT) + N,N‐dimethyltryptamine (DMT) were the primary alkaloids in all genotypes. No apparent relationships existed between palatability and individual alkaloid type. Results of 372 alkaloid determinations over three gratings in the 1st year indicated a negative correlation (r = ‐0.83) between total alkaloid percentage and relative palatability. The linear relationship was strongest between palatability ratings 5 to 10 on a scale of 1 (completely consumed) to 10 (completely rejected).Two groups of nine genotypes were clonally propagated to replicated plots for further grazing trials under restricted choice conditions during the 2nd year. When the groups were grazed separately in balanced lattice designs, relative palatability and total alkaloid concentration were linearly related (r = ‐0.95 and ‐0.92) in two experiments. These variables were also linearly related (r = ‐0.95) when the 18 clones were later grazed together in a randomized complete block design.Alkaloid concentrations in the 18 clones ranged from 0.18% to 1.21% of the dry matter and were similar between years and between grazings. Palatability ratings were also generally similar under the several different grazings situations.We concluded that determination of total alkaloid concentration is a valid means of screening for palatability in reed canarygrass.

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