In commercial practice, infill planks are dimensioned on the basis of company-internal experience. A lack of systematic data on the impact resistance of infill materials and little verified knowledge on the impact load of horse kicks permit no more than a rough plank thicknessrecommendation. As a consequence, the kick resistance of horse stable interior partitioning cannot be assessed by a defined standard. This meansthat in case of material failure and resulting injuries, compensation claims are foreseeable and objective judgements are hard to reach. This paper aims, therefore, to form a basis to enable the construction of kick resistant and, consequently, low-injury risk horse stables in the future. With this intention, an overview of the current status of testing for the impact bending strength of wood, particularly large dimensioned samples, and horse kick impact load determination is given. Additionally, results of impact bending tests on infill planks are presented and discussed. In addition, promising alternative wood species and engineered wood products are proposed as substitutesfor the use of tropical timber as plank material. Finally, the mechanical properties of laminated bamboo lumber, a popular plank material, are presented.
Kicking, a stereotypical behaviour by horses, can be seen as a response to poor animal welfare conditions and environmental stress (Broom, 1983). Despite the fact that horses are social animals, housing in single-stalls or pens is still common. Box design with a minimum contact between neighbouring horsesis one main factor for the increased abnormal behaviour of confined horses(McGreevy et al., 1995). Stereotypic behaviour has no function and can be either frustration-induced or malfunction-induced (Mason & Rushen, 2006). Among classic equine stereotypeslike weaving (locomotion) or cribbing (oral), stall or wall kicking can be categorised as self-mutilation (McDonnell, 2011). As long as the kicking force islow,stall kicking can be considered a bad habit. However, powerful kicks may cause material failure, legs can get stuck and result in life-threatening injuries when releasing or – in the worst-case scenario – not releasing the horse after it gets stuck.
The focus of horse kick impact load determination has to be placed on infill planks, because most kicking damage occurs in the lower 5 feet (∼ 1.5 m) of the partition, which is commonly built of rough cut, tongue and groove wood planks (Wheeler et al., 2002). In 2011, von Wachenfeldt et al. published a study aiming at the reduction of injury and accident risk for kicking horses with correct structural design and an appropriate choice of building materials and stall shape. For this purpose, the kick impact load by horses on fittings and building construction was determined by placing a measuring wall equipped with load cells and a computerized measuring system in a number of horse stables. Based on impact load and kick duration, measured for the greatest impact caused by a horse kick, an impulse of 150 Ns was suggested to be relevant while taking a certain safety margin into account. Derived from this, the impact resistance demand for horse stable elements was proposed to be equivalent to 350 Joule. Further research in this field is currently being conducted by the German Agriculture Society (DLG) at its Test Center Technology and Farm Inputs, Groß-Umstadt, Germany, as can be concluded from first publications (Gäckler, 2012; Glaser, 2012). In contrast to von Wachenfeldt et al. (2011), Gäckler (2012) added a high-speed camera to the test set-up, meaning more detailed information can be expected on the impact energy of a horse kick.