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3. Food Animal 3 > Dehorning > Flashcards

Dehorning Flashcards

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1
Q

what is a horn?

A
  • Bone covered with highly keratinized skin, without hair or glands
  • Entire epidermis covering cornual process produces horn
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2
Q

when does the conual process become hollow in cattle?

A

Becomes hollowed out (pneumatized) at approximately 6 mo age in cattle

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3
Q

difference between cattle and goats cornual process

A
  • In goat, extends less into horn, but larger openings into frontal sinus
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4
Q

horn blood supply

A
  • cornual arteries and veins
    > branches of superficial temporal a & v
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5
Q

horn nerve supply in cattle

A
  • Cornual branch of zygomaticotemporal nerve (branch of trigeminal n)
  • Branches from 1st & 2nd cervical (C1 & C2) nerves may also innervate caudal horn region
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6
Q

horn nerve supply in goats

A
  • Cornual branch of
    zygomaticotemporal nerve, plus
  • Cornual branch of infratrochlear nerve (branch of trigeminal n)
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7
Q

indications for dehorning

A
  • Prevent injury:
    > To other animals in herd (carcass damage common in horned feedlot cattle)
    > To humans or other animals (e.g. horses or dogs used to handle/herd cattle)
    <><><><>
  • Improve stock management
  • Need less feed-bunk space in feedlots
  • Increase number of animals in confined areas
  • More easily & safely handle animals in confined areas
    <><><><>
  • Diseases of the horn:
    > Fracture of cornual process (may lead
    to sinusitis)
    > Abnormal horn growth, which interferes with vision or other soft tissues
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8
Q

dehorning Techniques for calves <2 mo

A
  • Chemical cauterization < 1 week
  • Disbudding (thermal cauterization)
  • Tube dehorner (Robert’s)
  • Surgical excision
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9
Q

dehorning Techniques for Older calves/cattle (surgical amputation)

A
  • Keystone dehorner
  • Dehorning saw
  • Electric dehorning saw
  • Fetotomy wire saw
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10
Q

when is it best to dehorn? why?

A
  • disbudding before 8 weeks of age, rather than dehorning when older
    > reduces risk of serious infection, as sinus is not openned into skull
  • avoid summer and autmn for dehorning (flies)
    > dehorn in early spring, late fall, winter
    <><><><>
  • Preferred age: Often performed at 2-3 wk age, along with castration
  • As soon as horn bud can be palpated, Pneumatization not yet present
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11
Q

considerations on age for dehorning

A
  • Major factor in determining method, along with personal preference
  • The older the animal, the greater the stress & risk
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12
Q

dehorning methods for calves <2 months
> restraint and anesthesia / analgesia

A

Except for young calves, best if restrained in chute
* Head usually pulled to the side with halter or nose tongs
* NSAIDs: Ketoprofen (3mg/kgIM or IV) most used. Meloxicam (0.5 mg/kg IM or IV)
* Local anesthesia

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13
Q

local anesthetic for horn removal in calves <2 mo?
consideration for goats?

A
  • Beneath frontal crest (lateral aspect of frontal bone), 1/2 distance between lateral canthus & base of horn
  • Inject lidocaine bilaterally in fan-like manner at depth of 1-3 cm (not just subcutaneously)
    <><><>
  • Goats also have innervation from infratrochlear nerve
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14
Q

dehorning nerve block in calves <2mo
- Failure of block from:

A
  • Not waiting long enough for block to take effect
  • Improper injection site (if inject only subcutaneously)
  • Significant innervation (branches of C1& C2) from caudal base of horn, especially in bulls
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15
Q

when performing a nerve block for dehorning, what can we do for goats or cattle with large horns?

A

Local infiltration around entire base of horn, without specific regional analgesia

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16
Q

how to sedate calves < 2 mo for dehorning? dose considerations?

A

Xylazine
- Usually decrease recommended dose by ≥ 50%
a. In older calves, to keep animal standing
b. In young animals, for greater margin of safety

17
Q

chemical cauterization methods
- when, how

A

A. Very young calves (< 1 wk old)
B. Potassium hydroxide or sodium hydroxide stick/paste

18
Q

thermal cauterization methods
- should we do this? how it works?
- technique?

A

(disbuddingiron, electric dehorner)
<><>
1. Most recommended method
2. Usually no hemorrhage
3. Usually heals within several weeks with minimal scarring
<><><><>
a. Place tip of hot iron over the horn bud
b. Rotate iron as burns through skin surrounding bud
c. Include 1 cm skin around periphery of bud
d. Limit burn to about 5 sec, then repeat as needed until skin is dark copper color

19
Q

Robert’s dehorningtrephine (tube dehorner)
- for who?
- technique?

A
  • Has been used in calves up to 4mo old
  • Select trephine (4 sizes) that easily covers horn bud plus 1 cm surrounding skin
    <><><><>
    a. Incise skin around horn bud by rotating trephine
    b. Dissect to base of bud by rotating trephine at different angles
    c. After couple of turns, can scoop out bud or remove it with scalpel or scissors
    d. Usually minimal hemorrhage, which is easily controlled
20
Q

surgical technique for dehorning in calves < 2mo

A
  • Surgical excision with scalpel, removing 1 cm skin around horn bud
21
Q

Dehorning older calves & cattle
- considerations about horn growth
- how to avoid horn scur
- instruments variables

A
  • If significant horn growth present (> 2-3 cm), usually some kind of surgical amputation must be performed
  • Avoid horn regeneration (“horn scur”) by removing 1 cm of skin around base of the horn
  • Various instruments: Indications for each basically depend on:
    a. Size of the horn
    b. Speed & ease of use
    c. Cosmetics
22
Q

Barnes’ dehorner (gouge)
- when we use this, how

A
  1. For older calves, with relatively small horns up to about 4 cm in diameter
  2. Select size that covers horn well (2 sizes)
  3. Fast & relatively little work
  4. Technique: Push down & open handles in 1 movement
    * Hemostasis
23
Q

Keystone dehorner (horn shears)
- what is this?
- options for tools and when we use them?
- not good for who?

A
  • for older calves
  • two sizes, both work like a guillotine
    <><>
    Small:
    a. For older calves
    b. Fast & relatively little work
    <><>
    Large:
    a. For mass dehorning, where cosmetic appearance not important (e.g. “tipping” feedlot cattle)
    b. Relatively fast, but heavy & clumsy to use
    <><><><>
  • Not recommended in adults due to skull fracture
24
Q

Dehorning saw (straight-backed or stiff-backed saw)
- when we use this?
- considerations, issues

A
  1. Older cattle (especially if ≥ 3 yr old)
  2. Slow & much work
  3. Almost impossible to change direction/angle of the cut, after the cut is within bone
  4. Increased soft-tissue trauma may make it difficult to grasp vessels
25
Q

Fetotomy wire saw
- when is this useful for dehorning
- pros and cons?

A
  1. Best for small number of older cattle, where postoperative appearance important
  2. Slow & the most work
  3. Best control of the direction/angle of the cut, even within bone
  4. Minimal hemorrhage due to heat generated by saw
26
Q

dehorning aftercare

A
  • Perioperative medication
  • Analgesic/anti-inflammatory medication (NSAIDs)
  • Fly spray
  • Do not feed from manger, in which feed may fall down on surgical site
  • Monitor for signs of hemorrhage for 12hr
27
Q

dehorning complications

A
  • Hemorrhage
  • Frontal sinusitis
    > Only if pneumatization present (i.e. > 6 mo old)
  • Regeneration (“hornscur”): Most common complication
28
Q

Cosmetic dehorning: older cattle
- when we do this? when is it not needed?
- technique?

A
  • Older show animals or expensive breeding stock
  • Not needed if animal dehorned properly with standard techniques at young age
    (i.e. proper dehorning of young animal more cosmetic than “cosmetic dehorning” of older animal)
    <><><><>
    1. Surgical prep & aseptic technique
    2. Fusiform incision around base of horn
    a. Incisions pass no more than 1 cm from base of horn
    b. Deepen incisions until reach bone
    3. Undermine enough skin for primary closure
    4. Hemostasis by ligation of cornual artery
    5. Using fetotomy wire saw, remove horn & its base on the frontal bone
    6. Close skin (usually mattress sutures due to significant tension)
29
Q

goats dehorning techniques?
- also, scent gland ablation? where are they? how to do it?

A
  • Similar techniques to calves
  • Scent gland ablation:
  • scent glands are located diffusely within the wrinkled hairless skin just caudomedial to the base of each horn
  • Disbudding iron: Swing wide or make a 2nd imprint with the iron caudomedially, in the scent-gland region
  • Surgical excision with scalpel: If include adequate skin in the incision during dehorning, will usually remove the scent glands

3. Food Animal 3 (23 decks)

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