A natural energy absorbent polymer composite: The equine hoof wall.
Abstract: The equine hoof has been considered as an efficient energy absorption layer that protects the skeletal elements from impact when galloping. In the present study, the hierarchical structure of a fresh equine hoof wall and the energy absorption mechanisms are investigated. Tubules are found embedded in the intertubular matrix forming the hoof wall at the microscale. Both tubules and intertubular areas consist of keratin cells, in which keratin crystalline intermediate filaments (IFs) and amorphous keratin fill the cytoskeletons. Cell sizes, shapes and IF fractions are different between tubular and intertubular regions. The structural differences between tubular and intertubular areas are correlated to the mechanical behavior of this material tested in dry, fresh and fully hydrated conditions. The stiffness and hardness in the tubule areas are higher than that in the intertubular areas in the dry and fresh samples when loaded along the hoof wall; however, once the samples are fully hydrated, the intertubular areas become stiffer than the tubular areas due to higher water absorption in these regions. The compression behavior of hoof in different loading speed and directions are also examined, with the isotropy and strain-rate dependence of mechanical properties documented. In the hoof walls, mechanistically the tubules serve as a reinforcement, which act to support the entire wall and prevent catastrophic failure under compression and impact loading. Elastic buckling and cracking of the tubules are observed after compression along the hoof wall, and no shear-banding or severe cracks are found in the intertubular areas even after 60% compression, indicating the highly efficient energy absorption properties, without failure, of the hoof wall structure. STATEMENT OF SIGNIFICANCE: The equine hoof wall is found to be an efficient energy absorbent natural polymer composite. Previous studies showed the microstructure and mechanical properties of the hoof wall in some perspective. However, the hierarchical structure of equine hoof wall from nano- to macro-scale as well as the energy absorption mechanisms at different strain rates and loading orientations remains unclear. The current study provides a thorough characterization of the hierarchical structure as well as the correlation between structure and mechanical behaviors. Energy dissipation mechanisms are also identified. The findings in the current research could provide inspirations on the designs of impact resistant and energy absorbent materials.
Copyright © 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2019-04-03 PubMed ID: 30951896DOI: 10.1016/j.actbio.2019.04.003Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research paper is a detailed examination of how the structure of an equine hoof can absorb impact efficiently and how it could be used to inform the development of resistant materials. The paper also compares the properties of the hoof in different conditions – dry, fresh, and fully hydrated.
Hierarchical Structure of an Equine Hoof
- The researchers examined the various levels of structure, from nano to macro, in the hoof wall of a horse.
- At a micro level, the hoof wall contains tubules embedded in the intertubular matrix. These structures are made up of keratin cells with crystalline intermediate filaments (IFs) and amorphous keratin in the cytoskeletons.
- The size and shape of the cells, as well as their IF fraction, differed depending on whether they were located in the tubular or intertubular regions.
Changes in Mechanical Behaviour
- The structure of the tubules and intertubular regions influenced the mechanical behaviour of the hoof under stress. This was also affected by the condition of the hoof, being dry, fresh or fully hydrated.
- In dry and fresh conditions, the areas with tubules were stiffer and harder than the intertubular areas when loaded along the wall.
- However, when fully hydrated, the intertubular areas became stiffer due to absorbing more water.
Energy Absorption and Compression Behaviour
- The paper underscores the role of the tubules in reinforcing the hoof and preventing failure under compression and impact loading. Elastic buckling and cracking are observed after compression, while no severe cracks were found in the intertubular areas even after 60% compression.
- Documenting isotropy and strain-rate dependence, the behaviour of the hoof under different loading speeds and directions was examined.
- These observations demonstrated the hoof wall’s superior energy absorption capability without a failure.
Significance of the Findings
- Understanding the equine hoof wall’s structure and mechanical behaviors can inspire designs for impact resistant and energy absorbent materials.
- By presenting a thorough characterization of the hierarchical structure and energy dissipation mechanisms within the hoof wall, this study fills a knowledge gap in the understanding of the equine hoof wall structure at different strain rates and loading orientations.
Cite This Article
APA
Huang W, Yaraghi NA, Yang W, Velazquez-Olivera A, Li Z, Ritchie RO, Kisailus D, Stover SM, McKittrick J.
(2019).
A natural energy absorbent polymer composite: The equine hoof wall.
Acta Biomater, 90, 267-277.
https://doi.org/10.1016/j.actbio.2019.04.003 Publication
Researcher Affiliations
- Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, United States.
- Materials Science and Engineering Program, University of California Riverside, Riverside, CA, United States.
- Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, United States.
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, United States.
- Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, United States.
- Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, United States.
- Materials Science and Engineering Program, University of California Riverside, Riverside, CA, United States; Department of Chemical and Environmental Engineering, University of California Riverside, Riverside, CA, United States.
- School of Veterinary Medicine, University of California Davis, Davis, CA, United States.
- Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, United States; Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, United States. Electronic address: jmckittrick@ucsd.edu.
MeSH Terms
- Animals
- Hoof and Claw / chemistry
- Hoof and Claw / metabolism
- Horses
- Keratins / chemistry
- Keratins / metabolism
- Stress, Mechanical
- Tensile Strength
Citations
This article has been cited 12 times.- Sung CHJ, Hao T, Fang H, Nguyen AT, Perricone V, Yu H, Huang W, Sarmiento E, Ornelas AFD, Lublin D, Wehling R, Farajollahi S, Arakaki A, Nepal D, Lord NP, Kisailus D. Biological and Biologically Inspired Functional Nanostructures: Insights into Structural, Optical, Thermal, and Sensing Applications. Adv Mater 2025 Dec;37(51):e09281.
- Lee N, Mun S, Johnson KL, Horstemeyer MF. The Function of Horn Ridges for Impact Damping. Biomimetics (Basel) 2024 Aug 22;9(8).
- Luu RK, Buehler MJ. BioinspiredLLM: Conversational Large Language Model for the Mechanics of Biological and Bio-Inspired Materials. Adv Sci (Weinh) 2024 Mar;11(10):e2306724.
- Aoun R, Charles I, DeRouen A, Takawira C, Lopez MJ. Shoe configuration effects on third phalanx and capsule motion of unaffected and laminitic equine hooves in-situ. PLoS One 2023;18(5):e0285475.
- Hobbs SJ, Curtis S, Martin J, Sinclair J, Clayton HM. Hoof Matters: Developing an Athletic Thoroughbred Hoof. Animals (Basel) 2022 Nov 11;12(22).
- Chen G, Lin T, Guo C, Richter L, Dai N. Bending Study of Six Biological Models for Design of High Strength and Tough Structures. Biomimetics (Basel) 2022 Oct 25;7(4).
- Horan K, Coburn J, Kourdache K, Day P, Carnall H, Brinkley L, Harborne D, Hammond L, Peterson M, Millard S, Pfau T. Hoof Impact and Foot-Off Accelerations in Galloping Thoroughbred Racehorses Trialling Eight Shoe-Surface Combinations. Animals (Basel) 2022 Aug 23;12(17).
- Yang K, Qin N, Zhou C, Wang B, Yu H, Li H, Yu H, Deng H. The Study of Mechanical Behaviors of Caprinae Horn Sheath under Pendulum Impact. Polymers (Basel) 2022 Aug 11;14(16).
- Sprio S, Ruffini A, Tampieri A. Biomorphic Transformations: A Leap Forward in Getting Nanostructured 3-D Bioceramics. Front Chem 2021;9:728907.
- Lazarus BS, Chadha C, Velasco-Hogan A, Barbosa JDV, Jasiuk I, Meyers MA. Engineering with keratin: A functional material and a source of bioinspiration. iScience 2021 Aug 20;24(8):102798.
- Wang B, Huang Y, Zhou B, Li W, Chen H. Nanoindentation and Hierarchy Structure of the Bovine Hoof Wall. Materials (Basel) 2021 Jan 8;14(2).
- Tian W, Liu H, Zhang Q, Su B, Xu W, Cong Q. Cushion Mechanism of Goat Hoof Bulb Tissues. Appl Bionics Biomech 2019;2019:3021576.
Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
