Horns and Antlers Flashcards
Purpose of horns and antlers
-great deterrents
-establish dominance
**not necessarily linked with longevity
Horn growth
-grow gradually from birth
- single point, not branched but vary in shape and size
-present in both males and females (but may be smaller in females)
What species have horns?
-Bovidae (ex. bison, buffalo, muskox, sheep/goat, gazelle, domestic cattle
What are horns made of?
-made of bony core covered with a sheath of keratin
Heat loss and horns
-horns provide a surface for losing heat in hot climates
-horns specialized for heat loss will have long bony core and thin keratin sheath
Ex. Longhorn cattle, kudu
Horns in colder climates
-relatively short bony cores and a thick keratin sheath
Ex. pyrenees sheep, Dall’s sheep
Growth rings in horns
-when stressed (calving, winters), the rate of horn growth is slower and horn is softer so wears faster
-However, number of rings is less than age because first calving and horn growth occurs after ~2 yrs
Horn structure
-similar to hoof
-made of tubules and intertubular horn
-dermis base serves as periosteum and has dermal papillae that elongate and thicken the horn
-horn wall/sheath grows from epithelium that covers dermis between papillae (sheath actually modified cornified stratum of epithelium)
Glossy sheen of horns
-soft outer layer (epiceras) gives glossy sheen
Vascularization of horns
-horns are very vascular
-difficult to stop bleeding, need heat/cauterization
Development of horns
-horns develop from germinal epithelium on top of bone
**it can be removed, damaged, or displaced
Dehorning
-should be done early in life but if not, need nerve blocks
Main nerve in cattle horn
-Cornual nerve (of zygomatico-temporal of maxillary nerve (V2)
Other nerve blocks in cattle that may be needed if cornual nerve not sufficient
-Frontal nerve
-infratrochlear nerve
-ring block around horn base
Nerve blocks in goats/sheep
-Cornual nerve of zygomatico-temporal nerve (V2)
-cornual branch of infratrochlear nerve (V1)
Rhino “horns”
-made of compact hair/dermal papillae
Giraffe horn
-not an extension of frontal bone
-develop from a separate cartilaginous bone
-horns present in both sexes
-have them since birth
Pronghorns
-differ from both horns and antlers
-only present in American pronghorns- only member in Antilocapridae family
-made of bony core and keratinous sheath
-branched and shed annually (different than typical horns)
Species that have Antlers and general information
-only present in males of Cervidae (and females of caribou/reindeer)
-no extension of frontal sinus
-vary in shape and size, with multiple points (branched)
Antler growth
-grow and shed annually
-growing antler made of cartilage with velvet skin; dry antler made of solid bone
-whole weight achieved within a few weeks; one of the fastest growing mammal tissues (next to gravid uterus)
Cervids and canine teeth
-sometimes have large canine teeth that have same purpose as antlers
-Muntjacs (barking deer) have both canines and antlers
Velvet antlers
-in demand for traditional oriental medicine
Where does antler come from?
-antler comes from antler pedical from frontal bone
Antler shedding
-pedicle is chewed up by osteoclasts and antlers are cast
-Caribou: often times males don’t have antlers in winter when food is scares because they shed them after large increases in testosterone. Allows females to outcompete them
Antlers and successive growth
-antlers get bigger in successive years for several years
-they will have a prime age though and eventually become weak/lose strength
Caribou/reindeer
- basically the same species with small differences. Reindeer is domesticated, caribou is wild
- females have antlers through winter giving them advantage at feeding grounds over males
Innervation of antlers
-infratrochlear nerve (of V1)
-Auriculopalpebral nerve (of VII)
-Zygomatico-temporal nerve (of V2)
-ring block around pedicle
**important for antler removal because of antler supplement market
