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Antlerogenesis

Antlerogenesis. How Antlers Grow Original Power Point Created by: Andy Harrison . Modified by GA Agriculture Education Curriculum Office July 2002. Nature of Antlers. One of the fastest tissue growth rates Only other tissue that rivals this rate is some cancers.

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Antlerogenesis

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  1. Antlerogenesis How Antlers Grow Original Power Point Created by: Andy Harrison Modified by GA Agriculture Education Curriculum Office July 2002

  2. Nature of Antlers • One of the fastest tissue growth rates • Only other tissue that rivals this rate is some cancers. • Has led to interest by the National Cancer Society

  3. Nature of Antlers • Modified bones • Structurally similar to normal bones • NOT “horns” • Horns are permanent structures that never shed and are never replaced. • Antlers are temporary structures found only in the deer family (Cervidae).

  4. Nature of Antlers • Begin to develop early in a buck’s life • Fawn bucks have small bony projections at a few months old. • In order to produce antlers, there must be a permanent base to grow them. • Located on frontal bones of skull – called pedicels

  5. Nature of Antlers • Fawn bucks rarely produce more than a small set of pedicels. • Often called “nubbin” or “button” bucks • During first 12 – 18 months, there are physiological changes that cause antlers to develop.

  6. Nature of Antlers • Function like any other bone: • Begin with the development of a protein framework • Composed primarily of cartilage covered by skin on the frontal portion of the skull • The skin contains small hairs that give the velvety appearance • Amount of protein in diet very important for growth

  7. What Makes Antlers Develop • Blood testosterone levels peak in rut • Another smaller spike occurs just prior to time of antler growth initiation • Not as dramatic as in rut period • Brain response to longer day length may cause spike. • An increase in serum testosterone levels changes behavior

  8. What Makes Antlers Grow • Development begins almost immediately after shedding of old antlers. • Scars quickly heal over - new buds appear within couple of weeks. • Growth is slow at first.

  9. What Makes Antlers Grow • Bucks are typically in poor condition after rut • AKA: Post Rut Mortality • Usually spend the spring season replenishing body losses • Minimum of 16% protein needed to produce the best antler growth • After body losses are replenished, focus is on antlers

  10. What Makes Antlers Grow • Appearance is coded in some part of the brain • Nervous system directs the building of antlers • Growth progresses from tip of antler bud • First formed as cartilage • Later replaced by hardened bone

  11. What Makes Antlers Grow • During time of growth, bucks travel in social groups of various numbers • If psychologically neutered at this time, bucks are aware of size of developing antlers of other bucks • May affect social hierarchy • Social position may be affected by size of antlers

  12. Antlers • Bucks cannot shed summer coat until antler growth is complete. • A grayish winter coat grows in as summer coat sheds.

  13. Antler Changes • Just prior to pre-breeding period: • Soft framework of antlers begins to mineralize • These minerals (calcium and phosphorous) were deposited during the previous growing season.

  14. Velvet Shed • Some believe that a formation of a “burr” at base of antlers shuts off blood supply. • Others believe that the depositing of minerals causes “hardening of arteries” which cuts off blood supply. • Velvet dies from lack of blood supply • The actual reason may be a combination of both.

  15. Velvet Shed • The entire process takes only a few hours. • Death & shedding produce large quantities of blood from blood vessels. • This stains the antlers to produce their characteristic color. • Additional staining arises from rubbing on vegetation.

  16. Antlers • Once velvet sheds, the buck “rubs” its antlers. • Rubbing is influenced by hormones and from the itching of dying tissue. • Remaining antlers are non-living tissue.

  17. Antlers • Many times portions are broken off in fighting. • As rut progresses, testosterone levels decline. This is due to: • breeding • physiological changes • Dominant bucks are usually first to shed.

  18. Antler Shed • Abscission layer then forms at base, which cuts off blood flow. • Related to dropping or depletion of testosterone • Occurrence of antler shed depends on time of year when rut ends.

  19. Antler Growth • Development of the antler bud is consistent in all areas of country from March 15 to April 15. • By mid-May the antlers extend well above head. • Brow tines develop in June. • Each tine is developed before another pair reaches completion.

  20. Antler Growth • In July ornamentation at base forms. • In September antler growth is near completion • Velvet shedding varies from range to range, depending on breeding date. • In October antlers are fully hardened.

  21. Antler Quality • There is no way to predict quality of antlers. • Some deer have the ability to reproduce pattern if antlers are damaged. • Three factors that affect antler quality: • Age • Nutrition • Genetics

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