[Frontiers in Bioscience E4, 2328-2339, June 1, 2012] 2328 A review of factors affecting antler composition and mechanics Tomas Landete-Castillejos 1,2,3 , Jose A. Estevez 2,3 , Francisco Ceacero 2,3,4 , Andres J. Garcia 1,2,3 , Laureano Gallego 1,3 1 IREC Sec Albacete, Universidad de Castilla-La Mancha, UCLM, Albacete, Spain, 2 Instituto de Desarrollo Regional, IDR, UCLM, Albacete, Spain, 3 ETSIA, UCLM, 02071 Albacete, Spain, 4 Institute of Animal Science, Praha, Czech Republic TABLE OF CONTENTS 1. Abstract 2. Preliminary considerations: advantages and constraints as a model for bone 3. Antlers as sexual secondary characters 4. Mechanical properties of antlers and internal bones in relation to their function 5. Factors affecting antler traits: physiological effort 6. Factors affecting antler traits: management and nutrition 7. Perspectives 8. Acknowledgements 9. References 1. ABSTRACT Antlers constitute the only mammal model for limb regeneration. A number of factors affect antler regeneration. In this review, we examine such factors and the potential consequences for organ regeneration. As body mineral stores are depleted to grow antlers, physiological exhaustion is shown in the mineral composition, mechanical performance and, according to preliminary studies, porosity of the antler bone material. Nutrition plays an important role in antler characteristics. Thus, antler composition can be used as a diagnostic tool to assess mineral deficiencies in deer. Studies on ecological effects of exceptional weather in plants suggest that minor minerals, particularly Mn, may disproportionately play roles in mechanical performance of bone material. This suggests that Mn (and perhaps other minerals) is essential to incorporate Ca and P from resorbed skeleton material into antlers. Apart from implications for game management, some effects may have applications for medicine. 2. ADVANTAGES AND CONSTRAINTS OF ANTLERS AS A MODEL FOR BONE Other papers in this volume have addressed the suitability of antlers as a model for organ regeneration and its uniqueness in being the only mammalian organ that is regenerated each year or, indeed, at all. We will concentrate in this paper on the factors that modulate such regeneration process (i.e., factors affecting characteristics of the grown antlers). When one thinks about regeneration, as in the case of amphibian limbs or antlers, it is very likely to have the naïve idea that regenerated limbs or organs will grow as efficiently as a normal limb or organ grows during foetal development and later on during postnatal growth. I.e., that the tip of the finger in a regenerated limb must have the same size, mechanical performance of bones and their mineral composition to the fingers in pre-existing limbs. However, what we have learnt from antlers is that this is not the case, and that the physiological effort made to grow antlers affects how each section of it is grown. By physiological effort or exhaustion we indicate, in fact, an