Show me the science For a detailed discourse on the science of antler growth, see Antler Growth: Nutritional and Endocrine Factors Fennessy, P.F. and Suttie, J.M.

Each year, antlers drop off and fully regenerate in a growth cycles.

Each antler growth cycle includes:

initiationrapid growth (velvet phase)mineralisationvelvet sheddingantler casting

Various factors control the different phases

Control of antler growth

Being male secondary sexual characters, both pedicle formation and the subsequent antler growth cycle is under the control of testosterone. Testosterone levels at the various stages of the growth cycle are shown in the following table.

The factor responsible for stimulating antler growth is insulin-like growth factor 1 ('IGF1'). The timing of the peak of IGF1 production is regulated by day length but the key factor influencing the amount of IGF1 production is nutrition. Good nutrition is therefore required to grow big antlers to the animal's full genetic potential. For more on the role of nutrition, see the section on quality.

Deer Industry Conference 2017

Friday, May 26, 2017 to Saturday, May 27, 2017

Venue: Te Wharewaka Function Centre, 2 Taranaki St (waterfront), Wellington Date: Friday 26th - Saturday 27th May 2017 Programme: Registration: www.eiseverywhere.com/ehome/229206 Accomodation: Details on the conference Industry Partnership: There are a number of sponsorship oppourtunities available for this years conference.

Please visit the conference website or get in touch with Pat Johnston on 03 477 1377 or email pat@dcms.co.nz for more information.

Environment

Under this section is a collection of the major pieces of legislation concerning soil and water protection that needs to be complied with in your on-farm operations.

A stock take of all the regional councils' approaches to managing water quality and the significance for deer farming (in terms of nitrogen, phosphorous, bacteria and sediment) was completed in March 2015. Please refer to the Science and Policy section under the DINZ Activity tab for links to the stock-take or further update.

Biology

Deer antlers are bony outgrowths of the skull. Deer antler tissue is nevertheless very different to the skull in both structure and composition.

Cell types The growing tip of the antler is composed of various types of cells (mesenchymal, pre-chondroblasts and chondroblasts) and is covered by a layer of tissue (comprising epidermis and dermis). The lower (non-growing) regions of the growing antler are composed of further types of cells again (chondroblasts and osteoblasts), as shown in the following diagram.

Antler composition Mature antler is similar to compact skeletal bone in compostion, being 25% calcium and 19% phosphorus. Organic matter contributes 39% to antler weight and water content is 8%.

Antler has greater tensile strength but less elasticity than the human tibia. Its resistance to impact is greater than ivory. It is able to absorb a considerable amount of energy under impact before breaking.

Blood supply Blood supply to the pedicles is from internal vascular supply to the frontal bones, from branches of the superficial temporal arteries. Below the pedicle, the superficial temporal arteries give rise to large lateral coronal arteries and smaller medial coronal artiers which ascend the antler in the vascular layer of the velvet to supply blood to the velvet and bone. Deoxygenated venal blood is returned through the antler core. One large vein accompanies the lateral arterial arteries and one smaller vein accompanies the medial arteries, both of which evenually join the superficial temporal vein. Blood supply diminishes as calcification progresses.

Innervation Innervation to the antler is by the trigeminal nerve by way of supraorbital temporal branches, which are close to the lateral and medial coronal arteries. The posterior border of the pedicle is also supplied by sensory branches of the first cervical nerves. Upon casting, the nerves degenerate back to the pedicle and regenerate upon antler re-generation.

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Antlers

Antlers grow annually from the pedicle of the frontal bone of male deer.

They are male secondary sexual characteristics, hence are only grown by stags, although in the wider Cervidae family, they also grow in female reindeer (also known as 'caribou' in North America). Antlers are quite unlike the horns of cattle, which do not regrow if removed correctly. Antlers also develop and mature in a manner different to horns and broadly two stages of antler development are recognised: velvet antler and hard antler.

Velvet antler is defined as growing antler which contains an abundant blood and nerve supply and which has a fully intact skin with a covering of soft fine hair. Hard antler is the antler when growth has ceased, calcification has occurred, and the skin, nerve and blood supply are no longer functional.

Function of antlers The functions of antlers are to:

establish and maintain the social order, by being a visible expression of dominanceattract hinds in oestrusdefend the stag or a harem of deer from attackprepare wallowsmark territory

In respect of dominance, the stag with the largest antlers tends to be dominant. This is evident by the temporary exhibition of dominance by a younger stag when the elder, dominant stag casts his antlers. (Older stags cast antlers first). The older stag resumes dominance upon the younger stag casting his antlers, despite neither of them having antlers at that stage. Occasionally dominance is attained by a stag that exhibits the most intimidating social behaviours.

Whilst hinds in oestrus preferentially seek the stag with the largest antlers, the lack of antlers does not impair a stag's ability to successfully mate a hind.

The male deer of most species develop a pair of antlers every year from bony outgrowths called pedicles at the top of the skull. In New Zealand, velvet antler is removed from red deer stags, wapiti (elk) stags and red/wapiti hybrid stags.

Velvet antler growth The annual growth cycle of antlers starts in spring with the rapid development of a soft cartilaginous core from each of the two pedicles. This core is covered with a layer of connective tissue, then skin with a dense covering of fine hair, and the whole antler is well supplied with blood vessels and nerves. Velvet antler is very sensitive during this growth phase, and the male deer are protective of it and non-aggressive. Velvet antlers grow very rapidly, at a rate of up to 2 cm a day. As growth occurs, cartilage is gradually replaced by bone by a process of calcification. When growth is complete, the antler ‘hardens’ or calcifies completely, the blood vessels at the junction between the pedicle and the antler close off, and the skin, nerves and connective tissue dry, shrivel and flake off. The bony cores remain as hard antler ready for the ‘rutting’ season in autumn, when the stags are aggressive and combative as they compete for hinds. At the end of the rutting season, in early spring, the pedicle-antler junction weakens and the antlers are cast naturally.

Deer velvet is a unique structure, because it is the only organised mammalian tissue that regrows completely, and it does so every year. Moreover it grows extraordinarily rapidly, and the rapid growth is likely to be regulated by pharmacodynamic substances that are either unique or that can be found in other tissues but are at particularly high concentrations in deer velvet. In Asia, the unique nature of deer velvet has no doubt contributed to its reputation as a powerful remedy.

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