Original Full Length Article Does nutrition affect bone porosity and mineral tissue distribution in deer antlers? The relationship between histology, mechanical properties and mineral composition T. Landete-Castillejos a, b, c, ⁎, J.D. Currey d , F. Ceacero b, e , A.J. García a, b, c , L. Gallego a, b , S. Gomez f a Animal Science Tech. Applied to Wildlife Management Res. Group, IREC Sec. Albacete, IREC (CSIC-UCLM-JCCM), Campus UCLM, 02071 Albacete, Spain b Departamento de Ciencia y Tecnología Agroforestal, ETSIA, Universidad de Castilla-La Mancha (UCLM), 02071 Albacete, Spain c Grupo de Recursos Cinegéticos, Instituto de Desarrollo Regional (IDR), Universidad de Castilla-La Mancha (UCLM), 02071 Albacete, Spain d Department of Biology, University of York, YO10 5DD York, UK e Department of Ethology, Institute of Animal Science, POB 1, CZ-104 01 Praha 10-Uhříněves, Czech Republic f Departamento de Anatomía Patológica, Facultad de Medicina, Universidad de Cádiz, 11071 Cádiz, Spain abstract article info Article history: Received 24 August 2011 Revised 21 October 2011 Accepted 26 October 2011 Available online 30 October 2011 Edited by: David Burr Keywords: Antler Porosity Histology Mechanical properties Mineral composition Nutrition It is well known that porosity has an inverse relationship with the mechanical properties of bones. We exam- ined cortical and trabecular porosity of antlers, and mineral composition, thickness and mechanical proper- ties in the cortical wall. Samples belonged to two deer populations: a captive population of an experimental farm having a high quality diet, and a free-ranging population feeding on plants of lower nutri- tive quality. As shown for minerals and mechanical properties in previous studies by our group, cortical and trabecular porosity increased from the base distally. Cortical porosity was always caused by the presence of incomplete primary osteons. Porosity increased along the length of the antler much more in deer with lower quality diet. Despite cortical porosity being inversely related to mechanical properties and positively with K, Zn and other minerals indicating physiological effort, it was these minerals and not porosity that sta- tistically better explained variability in mechanical properties. Histochemistry showed that the reason for this is that Zn is located around incomplete osteons and also in complete osteons that were still mineralizing, whereas K is located in non-osteonal bone, which constitutes a greater proportion of bone where osteons are incompletely mineralized. This suggests that, K, Zn and other minerals indicate reduction in mechanical per- formance even with little porosity. If a similar process occurred in internal bones, K, Zn and other minerals in the bone may be an early indicator of decrease in mechanical properties and future osteoporosis. In conclu- sion, porosity is related to diet and physiological effort in deer. © 2011 Elsevier Inc. All rights reserved. Introduction Considerable porosity, when the bone is mature, is a feature of compact bone of the internal skeleton that usually arises from an im- pairment of the relationship between bone resorption and bone for- mation during remodelling [1]. Porosity has a strong relationship with mechanical properties of bone, particularly material stiffness, measured as Young's modulus of elasticity E [2]. Small changes in porosity lead to disproportionately large losses in bone strength in internal bones [3,4]. However, there is one case of bone where porosity is not produced by remodelling: antlers. Because antlers are rather different from other bones, hence- forth we will refer to mature bones found inside an animal body, therefore wet in their physiological state, as ‘internal’ bones as op- posed to antler, which is external and dry when used [5]. Antlers are formed of primary bone with apparently no evidence of secondary osteons [6]. Antlers are interesting as bones both be- cause they have the greatest work to fracture and impact energy of all known bones [5,7], and also because they reflect the physiological effort along the axis of growth of the main beam [8,9]. Antlers grow so quickly [10,11], that they require a partial resorption of the internal bones of the animal, resulting in temporary physiological osteoporo- sis [12–14]. Differences have been found in antler specific gravity or other measures of antler bone density between penned animals fed whole- meal in comparison with animals feeding on pastures [15], or density of internal bones comparing deer from different areas [14]. It is likely that such differences were partly caused by differences in bone poros- ity. The clearest case of nutrition effects in antler histology was an increase in porosity and an impaired mineralization, because there was i) less bone in the antlers of the high-fluoride group and ii) the bone that was present was less mineralized compared to the low- fluoride group [16]. A case in which there is likely to be a great difference in porosity is that of antlers that were the subject of our previous studies. We Bone 50 (2012) 245–254 ⁎ Corresponding author at: Animal Science Tech. Applied to Wildlife Management Res. Group, IREC Sec. Albacete, Campus UCLM, 02071 Albacete, Spain. Fax: + 34 967 599233. E-mail address: Tomas.Landete@uclm.es (T. Landete-Castillejos). 8756-3282/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.bone.2011.10.026 Contents lists available at SciVerse ScienceDirect Bone journal homepage: www.elsevier.com/locate/bone