Will go into some detail about growth/casting of antlers as will attempt to shed light on some abnormalities later.
Deer born reach puberty grow pedicles from which antlers grow/cast seasonally.
Cycle starts about 1/4 way through gestation with an initial surge of testosterone in foetus leading to antlerogenic tissue development on the frontal bones from which the pedicles originate. These subsequently develop antlers at appropriate time.
The start of the cycle is bodyweight dependent. Well grown start gonadal activity earlier.pedicles grow initially. Roe buck kids can develop button antlers ( button bucks ) at 7/8 months. Cast in December then go into normal cycle. On the first occasion the skin over the the pedicles changes into velvet and antlers grow from the blastema ( ? stem cells ). In the following years when antlers are cast no scar tissue is formed as the blastema heals over with velvet from which antlers grow. Each year's antlers grow with increasing complexity characteristic to that species of deer until maturity then gradually go back.
Hormonal control is light /darkness dependent. Light on the retina changes into electrical impulses which act on the pineal gland ( third eye ) to produce Melatonin which actually reaches peak levels during hours of darkness. Longer darkness higher levels of melatonin.
This in turn acts on the pituitary gland to produce Prolactin in high levels which inhibits testosterone production. More light less darkness Melatonin levels go down followed by depression of Prolactin and testosterone levels increase initiating the development of velvet forming antlers. These grow until testosterone concentration rises high enough for mineralisation of the antlers and the velvet dies off and is rubbed off.Hard antlers. These persist until increasing darkness leads to more Melatonin production followed by elevation of Prolactin levels which depresses testosterone concentration and when drops below 1.9 ng/ml the antlers are cast. Followed by healing with velvet and cycle repeated .
In short day breeders (Reds, fallow, Sika ) Prolactin depresses testosterone production. however in long day breeders ( Roe ) Prolactin enhances the action of testosterone. Note this point as will come back to it at later stage.
Anyone wishing to comment or query have posted Antlers: Part one post .separately as lot more to come