Is it normal for my horse to eat bark?
06 May 2015
Researchers at the University of New England (NSW Australia) completed a survey of 497 Australian horse owners. 73% reported their horses eat foliage other than grass, such as shrubs, trees, leaves and twigs. Of note 31% specified their horses particularly eat bark.
It is not known why horses eat bark. Some have theorised it is due to mineral deficiency, fiber deficiency, increasing the variety in their diet or boredom. Previous studies have shown when given the option horses like to eat as wide a variety of vegetation as possible.
A paper published in the Australian Veterinary Journal in 1986 notes that 40 horses at the Queensland Agricultural College had a noticeable increase in bark eating behavior after being moved from non-irrigated to irrigated and improved pasture. Researchers at the college took the opportunity to examine the make-up of the different pastures, it was noted that while nitrogen content was similar, the grasses in the non-improved pasture were more than twice as high in fibre content. It was suggested that perhaps the horses were eating bark because they craved fiber.
Another study of wild horses in the Netherlands examined the mineral content of bark and concluded that mineral deficiencies were not the reason horses consumed bark. They also noticed horses preferred smooth, easy to strip bark from smaller and younger trees, particularly beech trees. This is consistent with observations from the Queensland Agricultural College where it was noted that the easy to strip, stringy bark trees were targeted most while the rougher ironbarks were pretty much left alone.
Further interesting results from the University of New England survey were that 85% of the respondents indicated that they feed their horses hay and/or grain, it was uncommon for horses to be sustained on pasture alone. Only 41% of the horses in the study were exercised, so supplemental feeding was not necessarily related to workload but perhaps related to pasture quality.
90% of owners reported a problem with pasture management with the most common problem being weeds (78.9% of respondents) followed by overgrazing (52.1%), compaction (40.4%) and water-logging (40.0%).
van den Berg, M., Brown, W. Y., Lee, C., & Hinch, G. N. (2014). Browse-related behaviors of pastured horses in Australia: A survey. Journal of Veterinary Behavior: Clinical Applications and Research.
Kuiters, A. T., Van der Sluijs, L. A. M., & Wytema, G. A. (2006). Selective bark-stripping of beech, Fagus sylvatica, by free-ranging horses. Forest ecology and management, 222(1), 1-8.
Keenan, D. M. (1986). Bark chewing by horses grazed on irrigated pasture. Australian veterinary journal, 63(7), 234-235.