Question

My sensitive Thoroughbred gelding has a history of allergies and asthma to most grasses, trees, and insects. He is also prone to lymphangitis. Recently, he has experienced mild colic after two consecutive days of turnout on pasture containing flowering birdsfoot trefoil. Does this type of forage cause digestive discomfort when flowering?

Answer

Birdsfoot trefoil is a perennial legume adapted to humid, temperate regions. The plant grows in a wide range of soils and tolerates both drought and flooding. As part of its growth cycle, birdsfoot trefoil forms bright yellow flowers. “The name ‘birdsfoot’ is derived from the claw-like arrangement of seed pods that develop following pollination of the flowers,” according to Forages: An Introduction to Grassland Agriculture.^*

Certain properties of birdsfoot trefoil may be responsible for causing colic. One could be the high tannin content. While this characteristic is what makes birdsfoot trefoil less likely to induce bloat in other species, it could cause mild stomach discomfort in sensitive animals. Birdsfoot trefoil is susceptible to Fusarium contamination, which is a fungus that, given the necessary environment, can produce a mycotoxin capable of causing colic symptoms in horses. Finally, certain types of birdsfoot trefoil have a tendency to accumulate prussic acid, particularly during drought, and this can instigate colic and other problems.

In short, birdsfoot trefoil may be causing the problem you describe, but it is difficult to know with certainty. Under normal circumstances, birdsfoot trefoil is a satisfactory forage for horses. To play it safe, you could completely remove the horse from the birdsfoot trefoil or make sure the horse has access to other forage when consuming trefoil, which will serve to dilute any toxins.

With respect to its growth stage, I can’t find any specific information on flowering birdsfoot trefoil that contradicts or differs from consumption of the legume at any other stage of growth.

As with all health concerns, a veterinarian should be called in immediately. Recurrent colic can be a sign of a serious health problem.

^*Sheaffer, C.C., M.S. Wells, and C.J. Nelson. 2018. Legumes for northern areas. In: M. Collins, C.J. Nelson, K.J. Moore, and R.F. Barnes, editors, Forages: An Introduction to Grassland Agriculture, Vol. I. John Wiley & Sons, Hoboken, NJ. p. 121-122.