Horns are permanent structures projecting from the head of bovids, consisting of a bony horncore covered with a layer of skin and then a sheath of keratinous material showing variability of growth intensity based on nutrition. From the point of view of the horn's mechanical properties, the keratin sheath has been widely studied, but only a few studies have considered the complete structure of the horn and fewer studies have focused on the bony horncore and its characteristics. The latter showed the important role of the bony core, when cranial appendages are subject to mechanical stress (as happens during fighting). The mechanical properties of bone material, along with its mineral profile, are also important, because they can show effects of different factors, such as nutrition and mineral deficiencies in diet. For this reason, eight horncores of captive common eland male were sampled at four positions along the vertical axis of the horn. The main aim was to study variation in mechanical properties and the mineral content along the vertical axis of the horncores. We further analysed whether the spiral bony ridge present on eland horncores differs in any of the studied properties from adjacent parts of the horncore. In other antelopes, spiral ridges on the horns have been proposed to increase grip during wrestling between males. Cross-sections of the horncores were performed at four positions along the longitudinal axis and, for each position, two bone bars were extracted to be tested in impact and bending. Moreover, in the first sampling position (the closest position to the base) two bars were extracted from the spiralled bony area. The resulting fragments were used to measure ash content, bone density and mineral content. Results showed that horn bone decreased along the vertical axis, in ash (-36%), density (-32%), and in impact work 'U' (marginally significant but large effect: -48%). The concentration of several minerals decreased significantly (Mg, Cr, Mn and Tl by -33%, -25%, -31%, -43%, respectively) between the basal and the uppermost sampling site. The bone tissue of the horncore spiral compared with non-spiral bone of the same position showed a lower ash content (53% vs. 57%), Mg and Mn; in addition to showing approximately half values in work to peak force 'W', bending strength 'BS' and 'U', but not in Young's modulus of elasticity 'E'. In conclusion, similarly to the results in a totally different fighting bony structure, the antlers, the horncore of eland shows advantageous parameters in bone tissue of the base in respect to the tip, with higher values for mechanical properties, density and mineral profile. Moreover, the spiral bone tissue showed lower material mechanical properties. Probably the spiral tissue of the horn may have a role in deflecting potential cross-sectional fractures during wrestling. In addition, it may serve to improve the grip during wrestling, and we propose that it may also prevent risk of rotation of sheath with respect to internal bone not only in this, but also in other straight bovid horns.

Departamento de Ciencia y Tecnología Agroforestal y Genética Universidad de Castilla La Mancha ETSIAM Albacete Spain

Department of Animal Science and Food Processing Faculty of Tropical AgriSciences Czech University of Life Sciences Prague Prague 6 Suchdol Czech Republic

Department of Ethology Institute of Animal Science Prague 10 Uhříněves Czech Republic

Instituto de Investigación en Recursos Cinegéticos IREC UCLM Campus Universitario s n Albacete Spain

Sección de Recursos Cinegéticos y Ganaderos Instituto de Desarrollo Regional Albacete Spain

See more in PubMed

Bartoň L, Bureš D, Kotrba R, et al. (2014) Comparison of meat quality between eland (Taurotragus oryx) and cattle (Bos taurus) raised under similar conditions. Meat Sci 96, 346–352. PubMed

Bubenik GA, Bubenik AB (1990) Epigenetical, Morphological, Physiological, and Behavioral aspects of evolution of horns, pronghorns, and antlers In: Horns, Pronghorns, and Antlers: Evolution, Morphology, Physiology, and Social Significance. (eds Bubenik GA, Bubenik AB.), pp. 561 New York: Springer Science & Business Media. PubMed

Caro TM, Graham CM, Stoner CJ, et al. (2003) Correlates of horn and antlers shape in bovids and cervids. Behav Ecol Sociobiol 55, 32–41.

Currey JD (1984) Effects of differences in mineralization on the mechanical properties of bone. Philos Trans R Soc Lond B Biol Sci 304(1121), 509–518. PubMed

Currey JD (2002) Bones: Structure and Mechanics. Princeton, USA: University Press.

Currey JD, Landete‐Castillejos T, Estevez JA, et al. (2009) The Young's Modulus and impact energy absorption of wet and dry deer cortical bone. Bone 1, 38–45.

Davis EB, Brakora KA, Lee AH (2011) Evolution of ruminant headgear: a review. Proc R Soc B 278, 2857–2865. PubMed PMC

Drake A, Donahue TLH, Stansloski M, et al. (2016) Horn and horn core trabecular bone of bighorn sheep rams absorbs impact energy and reduces brain cavity accelerations during high impact ramming of the skull. Acta Biomater 16, 30 415–30 419. PubMed

Estevez JA, Landete‐Castillejos T, Martínez A, et al. (2009) Antler mineral composition of Iberian red deer Cervus elaphus hispanicus is related to mineral profile of diet. Acta Theriol 54, 235–242.

Geist V (1966) The evolution of horn‐like organs. Behaviour 27, 175–214.

Gomez S, Garcia AJ, Luna S, et al. (2013) Labeling studies on cortical bone formation in the antlers of red deer (Cervus elaphus). Bone 52, 506–515. PubMed

Jeffery RCV, Hanks J (1981) Age determination of eland Taurotragus oryx (Pallas, 1766) in Natal Highveld. S Afr J Zool 16, 113–122.

Kerry MA, Roth HH (1970) Studies on the agricultural utilization of semi‐domesticated eland (Taurotragus oryx) in Rhodesia. Rhod J Agric Res 8, 149–155.

Kiley‐Worthington M (1978) Causation, evolution and function of visual displays of eland (Taurotragus oryx). Behaviour 66, 179–222.

Kingdon J (1982) East African mammals. An atlas of evolution in Africa. Volume 3Part C (Bovids). London, UK: Academic Press.

Kitchener A, Vincent JFV (1987) Composite theory and the effect of water on the stiffness of horn keratin. J Mater Sci 22, 1385–1389.

Landete‐Castillejos T, Estevez JA, Martínez A, et al. (2007) Does chemical composition of antler bone reflect the physiological effort? Bone 40, 1095–1102. PubMed

Landete‐Castillejos T, Currey JD, Estevez JA, et al. (2010) Do drastic weather effects on diet influence changes in chemical composition, mechanical properties and structure in deer antlers? Bone 47, 815–825. PubMed

Landete‐Castillejos T, Currey JD, Ceacero F, et al. (2012) Does nutrition affect bone porosity and mineral tissue distribution in deer antlers? The relationship between histology, mechanical properties and mineral composition. Bone 50, 245–254. PubMed

Li BW, Zhao HP, Feng XQ, et al. (2010) Experimental study on the mechanical properties of the horn sheaths from cattle. J Exp Biol 213, 479–486. PubMed

Li BW, Zhao HP, Feng XQ (2011) Static and dynamic mechanical properties of cattle horns. Materials Sci Eng C 31, 179–183.

Lundrigan B (1996) Morphology of horns and fighting behaviour in the family of Bovidae. J Mammal 77, 462–475.

Martínez M (2015) Social Structures among Different Groups in Common Eland. MSc. thesis, Suchdol‐Prague, Czech Republic: Czech University of Life Sciences Prague, pp 59.

McKittrick J, Chen PY, Bodde SG, et al. (2012) The structure, functions, and mechanical properties of keratin. Jom 64, 449–468.

Monteith KL, Long RA, Bleich VC, et al. (2013) Effects of harvest, culture, and climate on trends in size of horn‐like structures in trophy ungulates. Wildl Monogr 183, 1–26.

Olguín CA, Landete‐Castillejos T, Ceacero F, et al. (2013) Effects of feed supplementation on mineral composition, mechanical properties and structure in femurs of Iberian Red Deer hinds (Cervus elaphus hispanicus). PLoS One 8, e65461. PubMed PMC

Rowe‐Rowe DT (1983) Habitat preferences of five Drakensberg antelopes. S Afr J Wildl Res 16, 1–8.

Solounias N (2007) Family Bovidae In: The Evolution of Artiodactyls. (eds Prothero DR, Foss SE.), pp. 384 Maryland, USA: Johns Hopkins University Press.

Toledano‐Diaz A, Santiago‐Moreno J, Gomez‐Brunet A, et al. (2007) Horn growth related to testosterone secretion in two wild Mediterranean ruminant species: the Spanish ibex and European Mouflon. Anim Reprod Sci 102, 300–307. PubMed

Tombolato L, Notitskaya EE, Chen P, et al. (2010) Microstructure, elastic properties and deformation mechanisms of horn keratin. Acta Biomater 6, 319–330. PubMed

Tomlinson DJ, Mulling CH, Fakler TM (2004) Formation of keratins in the bovine claw: roles of hormones, minerals and vitamins in functional claw integrity. J Dairy Sci 87, 797–809. PubMed

Vadlejch J, Kotrba R, Čadková Z, et al. (2015) Effects of age, sex, lactation and social dominance on faecal egg count patterns of gastrointestinal nematodes in farmed eland (Taurotragus oryx). Prev Vet Med 121, 265–272. PubMed

Zhu B, Zhang M, Zhao J (2016) Microstructure and mechanical properties of sheep horn. Microsc Res Techinq 79, 664–674. PubMed

Horn size is linked to Sertoli cell efficiency and sperm size homogeneity during sexual development in common eland (Taurotragus oryx)