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

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

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

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

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

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

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

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

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

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

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

13. Antler Changes Just prior to pre-breeding period: Just prior to pre-breeding period: Soft framework of antlers begins to mineralize Soft framework of antlers begins to mineralize These minerals (calcium and phosphorous) were deposited during the previous growing season. 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. 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. Others believe that the depositing of minerals causes “hardening of arteries” which cuts off blood supply. Velvet dies from lack of blood supply Velvet dies from lack of blood supply The actual reason may be a combination of both. The actual reason may be a combination of both.

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

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

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

18. Antler Shed Abscission layer then forms at base, which cuts off blood flow. Abscission layer then forms at base, which cuts off blood flow. Related to dropping or depletion of testosterone Related to dropping or depletion of testosterone Occurrence of antler shed depends on time of year when rut ends. 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. 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. By mid-May the antlers extend well above head. Brow tines develop in June. Brow tines develop in June. Each tine is developed before another pair reaches completion. Each tine is developed before another pair reaches completion.

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

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