Phytochemical complementarities among endophyte-infected tall fescue, reed canarygrass, birdsfoot trefoil and alfalfa affect cattle foraging

Summary

This controlled grazing trial demonstrated that cattle foraging behaviour on high-alkaloid grasses is substantially influenced by both the sequence in which they encounter complementary phytochemical sources and the presence of tannin- or saponin-rich forages. When cattle first grazed on tannin-rich birdsfoot trefoil or saponin-rich alfalfa before accessing high-alkaloid grasses, they markedly increased use of those grasses throughout the trial, suggesting that secondary compounds consumed sequentially can modulate subsequent foraging preferences and potentially reduce the absorption of alkaloids.

Regional applicability

The findings are relevant to United Kingdom livestock systems, particularly in mixed grassland and legume-based pastures. However, the study used endophyte-infected tall fescue and reed canarygrass under what appear to be North American conditions; direct transfer to UK forage species and climate contexts would require validation, though the principles of phytochemical complementarity are likely broadly applicable.

Key measures

Incidence of foraging on each plant species (%) determined by scan samples at 2-minute intervals; alkaloid, tannin and saponin concentrations in plant species; foraging duration and temporal patterns

Outcomes reported

The study measured cattle foraging incidence (%) on four forage species varying in alkaloid, tannin and saponin concentrations across two sequential grazing phases. It examined how ingestion sequence and phytochemical composition influenced cattle dietary choices and foraging patterns over a 12-day trial.

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