Abstract
Bone ash, collagen, Ca and P composition, are considered the main factors affecting mechanical properties in bones. However, a series of studies in bone and antler have shown that some trace minerals, such as manganese, may play a role whose importance exceeds what may be expected considering their low content. A previous study showed that a reduction in manganese in antlers during a year of late winter frosts led to generalized antler breakage in Spain, which included a reduction of 30% of cortical thickness, 27% reduction in impact energy, and 10% reduction in work to peak force. Starting for this observation, we experimentally studied the effects of manganese supplementation in adults and yearling (yearlings) red deer under a balanced diet. Subjects were 29 deer of different age classes (adult n = 19, yearlings n = 10) that were divided in a manganese injected group (n = 14) and a control group (n = 15). Antler content in ashes and minerals, intrinsic mechanical properties and cross section structure were examined at 4 points along the antler beam. A one way ANOVA (mean per antler) showed that in yearlings, manganese supplementation only increased its content and that of Fe. However, in adults, Mn supplementation increased the mean content per antler of Ca, Na, P, B, Co, Cu, K, Mn, Ni, Se (while Si content was reduced), and impact work but not Young’s modulus of elasticity, bending strength or work to peak force. A GLM series on characteristics in the uppermost part examined in the antler, often showing physiological exhaustion and depletion of body stores, showed also a 16% increase in work to peak force in the antlers of the treated group. Thus, manganese supplementation altered mineral composition of antler and improved structure and some mechanical properties despite animals having a balanced diet.
Highlights
Antler, which is true bone despite being used when dry and having some unusual features such as the lowest ash content of all bones [1], has attracted the attention of researchers in bone mechanics [2, 3, 4] because, among mammalian bones, it has the highest work to peak force, that is, the amount of work needed to break specimens [2], and it is difficult to break in impact [1, 5]
Previous studies by our group have shown that the composition, mechanical properties, and structure of deer antlers, or even their histology [11, 13] could be influenced by diet, and natural factors likely affecting mineral composition of plants on which deer feed [4, 6, 7, 14]
Primary osteons were completely formed both at position 1 and 4 (Fig 1), osteons in cortical bone did not show osteomalacic seams
Summary
Antler, which is true bone despite being used when dry and having some unusual features such as the lowest ash content of all bones [1], has attracted the attention of researchers in bone mechanics [2, 3, 4] because, among mammalian bones, it has the highest work to peak force, that is, the amount of work needed to break specimens [2], and it is difficult to break in impact [1, 5]. A series of studies [6,7,8] have shown that antlers are an excellent model for studying bone biology: i) because they are accessible without surgery; ii) because they grow quickly (with an average of 0.67 cm/d [9] in red deer) and demand a high mineral transfer from the skeleton [10]. That because this fast growth leaves little room for remodeling [11], and shows more clearly nutrition or other effects than in internal bone, which is a mosaic of parts build in different times of the life of an animal. In 2010, a study by Landete-Castillejos et al [4], concluded that among the changes in composition produced in deer antlers by an event of extraordinary low temperatures at the onset of plant sprout, it was Mn decrease which produced a 27% reduction in impact energy, 10% reduction in work to peak force, 30% reduction in antler weight, and 18% reduction in cortical thickness
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