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Dermatology 2 > Farm animal dermatology > Flashcards

Farm animal dermatology Flashcards

Dermatological disease, Teat surgery

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1
Q

What would you differential diagnoses be if presented with a group of cows showing the following clinical signs?

  • All affected animals are pyrexic
  • Recumbent heifers dyspnoeic, swollen muzzles and nostrils, seroud oronasal discharge
  • Marked skin tent
  • Generalised erythema and alopecaiaon white haired areas
A
  • Ingestion of toxins
  • Bluetongue
  • Vasculitis
  • Foot and mouth disease
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2
Q

Describe the appearance of photosensitisation in cows

A
  • Can be primary or secondary
  • Erythema on white areas
  • Tachycardia
  • Dyspnoea
  • Oculonasal discharge
  • Secondary: icterus, depression, other behavioural changes
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3
Q

What can cause photosensitisation in cows?

A

Ingestion of toxins, anything affecting liver function preventing ability to excrete harmful compounds

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4
Q

Describe the mechanisms of action of ragwort toxicity

A
  • Toxin is pyrrolizidine alkaloid
  • Converted to toxic intermediates pyrroles and their esters
  • Cause damage to hepatocytes
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5
Q

Explain the pathogenesis of photosensitisation skin lesions due to ingestion of toxic compounds causing liver damage

A
  • Liver non-functional so toxic compounds build up in blood

- Reach skin, react with sunlight leading to photosensitisation

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6
Q

What diagnostic tests should be carried out if are suspicious of photosensitisation as a consequence of liver damage?

A
  • Blood sample to assess liver function (serum biochem for liver enzymes)
  • Ultrasonography
  • Biopsy of liver
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7
Q

Compare the bilirubin and bile acid concentrations in primary photosensitisation vs ragwort poisoning

A
  • Would be normal in primary photosensitisation

- Elevated in ragwort poisoning

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8
Q

What features may be identified on liver biopsy in the case of ragwort poisoning?

A

Megalocytosis, biliohyperplasia and fibrosis

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9
Q

Outline a treatment plan for cattle suffering ragwort toxicity

A
  • No corrective treatment for liver damage
  • Supportive treatment
  • Small frequent meals 6x/day
  • Oral or parenteral B vitamins
  • Fluids
  • Euthanasia
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10
Q

What dietary management is appropriate in secondary photosensitisation?

A
  • Low protein, high energy diet

- Rich in branched chain amino acids

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11
Q

If all liver values are normal in a ruminant with photosensitisation, what does this indicate?

A

That this is primary photosensitisation and no evidence of liver damage

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12
Q

Outline the potential causative agents of primary photosensitisation in cattle

A
  • Diet
  • Inherited defect in animal’s metabolism of red blood cells
  • Ingestion of lush green plants containing photodynamic compounds e.g. St, John’s wort, clover
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13
Q

What is the prognosis for a cow with primary photosensitisation as a consequence of St John’s Wort ingestion?

A

Can recover, but if caught too late can be fatal

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14
Q

Give the methods of restraint that can be used for cow in order to examine the udder

A
  • Lifting back leg
  • Tail jack
  • Tie back leg
  • Kickbar (usually ineffective)
  • Crush/WOPA box/parlour
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15
Q

List the methods for providing anaesthesia to a teat in cows

A
  • Teat cistern infusion
  • Ring-block
  • Paravertebral nerve block
  • Lumbosacral epidural
  • Line block
  • Topical (splash) application
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16
Q

Describe the method for a teat cistern infusion and state what is anaesthetised by this method

A
  • 5-10ml of local anaesthetic via teat canal into teat cistern
  • Blocks mucosal layer of teat but NOT connective tissue or muscle
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17
Q

Describe the method for a ring block to anaesthetise a cow’s teat and state which structures are anaesthetised by this method

A
  • Inject local anaesthetic in a ring pattern around the base of the teat, full thickness
  • Blocks mucosa and connective tissue
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18
Q

Why would you want to avoid using procaine for tea surgery?

A

Procaine always comes with adrenaline in the UK and and to avoid the vasoconstrictive effect this would have as this could present a risk for necrosis of the teat

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19
Q

What is blocked by a paraveertebral nerve block?

A

Cranial udder and teats (used for standing surgery)

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20
Q

What is blocked by a lumbosacral epidural and how must surgery using this technique be performed?

A
  • Anaesthesia of caudal abdominal wall up to level of umbilicus, with temporary dysfunction of the hindlimbs
  • Need sedation and lateral recumbency for surgery
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21
Q

Describe the method for a line block for teat surgery and outline the key risks

A
  • Give multiple subcut infiltrative injections of local anaesthetic 0.5-cm apart at wound edge to required depth
  • Risk of oedema and haemorrhage delaying wound healing, but technique is quick and easy
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22
Q

Describe the method and main advantage of a topical (splash) application of local anaesthetic for teat surgery

A
  • Drip or splash LA onto surgical wound and allow ~20mins contact time for it to take effect
  • Can be used before infiltrative anaesthesia in fractious animals
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23
Q

Discuss the use of bandages in teat repair

A
  • Applied to keep teat clean
  • Rarely used
  • May want to use after surgical repair
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24
Q

What is the main indication for use of staples in teat repair? Advantages and disadvantages

A
  • Superficial wounds only
  • If laceration is affecting teat canal may end up with fistulas
  • But are quick and cheap
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25
Q

What is the main indication for the use of self-retaining cannulas/milk catheters?

A

To allow drainage of milk from a teat where milking is not possible e.g. due to full thickness perforated lesion. Milk drips out slowly

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26
Q

What are the main risks with self-retaining cannulas/milk catheters?

A
  • End of cannula is always open and can introduce infection (unless place bung)
  • Plug replacement often forgotten after allowing udder to drain
  • Total cannula falls out or accidentally left open, both present risk for infection
27
Q

Briefly describe the closure of teat lacerations

A
  • Need to close each layer individually i.e. submucosal, then connective tissue, then muscle, then skin
  • Cannot be milked while wound heals
28
Q

When is teat amputation indicated and why?

A
  • Where more than 3/4 of the teat has ripped off

- Repair would leave too much scar tissue, which would affect milk flow and increasing the risk of chronic infection

29
Q

What is a good prognostic factor for teat amputation?

A

If can perform surgery within 4 hours of injury occurring then good, if overnight then poor prognosis

30
Q

What is the main risk when performing a teat amputation?

A

Go too high into venous plexus - may bleed a lot but not too much of a worry, will need antibiotics

31
Q

What are the methods available for the removal of teat granulomas, and ourline the surgical requirements?

A

For all methods require local block

  • Hudon’s teat spiral
  • Alligator forceps
  • Theloscopy
32
Q

Describe the cause and consequences of a teat pea/granuloma

A
  • Unsure of cause, may be infection, haematoma, calculi, papilloma
  • Slows milking
33
Q

Discuss the use of Hudson’s teat spiral for the removal of teat granulomas (advantages, disadvantages)

A
  • Difficult to use
  • Insert spiral via streak canal, take pea into spiral and remove pea
  • Likely to be painful, requires anaesthetic
  • Likely to cause damage to teat sphincter which increases risk of mastitis due to improper closure following milking
34
Q

Discuss the use of alligator forceps for the removal of teat granulomas

A
  • Easier than Hudson’s teat spiral

- But risk of sphincter damage

35
Q

Discuss the use of theloscopy for the removal of teat granulomas

A
  • Teat endoscopy, very rare
  • Only very valuable cows
  • Incision on side of teat, use endoscope to remove pea via the side of the teat
36
Q

Discuss the use of teat knives (aim, method, risks, post-procedural requirements)

A
  • Used to “repair” hard milkers or teat spiders
  • Causes damage to teat canal
  • Aim to speed up milking
  • Insert knife into base of teat and make incision, rotate 90degrees and made a second incision
  • Can be effective
  • Ensure keep milking cow to keep incision open
  • High risk of infection, bigger problem than slow milking quarter…
37
Q

What is the legislation regarding chemical anaesthetic in the disbudding of cows?

A
  • Must use chemical anaesthetic other than when chemical cauterisation is used
  • Chemical cauterisation only in first week of life
38
Q

When should dehorning be avoided and why?

A

Avoid in summer due to high risk of fly strike and infection from flies

39
Q

Outline the options for restraint for dehorning in cattle

A
  • Good quality crush
  • Halter +/- bulldogs
  • Light sedation with xylazine/detomidine in fractious animals
  • Heavy sedation with the above to induce recumbency if no crush available or very fractious animal
40
Q

Outline the anaesthesia and analgesia used in dehorning of cattle

A
  • Cornual nerve block
  • Local block of subcutaneous branches of second cervical nerve
  • Allow time for anaesthesia to take effect (at least 10 mins)
  • Pain difficult to control in dehorning
  • Check by pricking around horn base with needle
  • NSAIDs
41
Q

Identify the methods for dehorning cattle

A
  • Remove horn close to/flush with skull
  • Scoop/gouge dehorners
  • Shears/guillotines
  • Embryotomy wite
  • Bone saw
42
Q

Give the advantages and disadvantages of scoop/gouge dehorners

A 
- E.g. Barnes dehorners
Advantages:
- Good for smaller horns
- Quick for small to medium/large horns
Available in variety of sizes

Disadvantages

  • Cumbersome
  • Require some strength to operate
43
Q

Give the advantages and disadvantages of shears/guillotine dehorners

A

Advantages:

  • Quick
  • Can be sued for small to very large horns quickly and cleanly

Disadvantages

  • Require considerable strenght
  • Cumbersome
  • Require long arms and lots of room
  • Anecdotally can fracture frontal bone in large animals
44
Q

Give the advantages and disadvantages of using embryotomy wire for dehorning cattle

A

Advantages:

  • Better haemostasis once hot
  • Less strength required

Disadvantages

  • Slow, stamina required
  • Tiring
45
Q

Give the advantages and disadvantages of bone saws for dehorning cattle

A

Relatively quick, effective if skilled

46
Q

Discuss the need for haemostasis in dehorning

A
  • 2-4 large arteries in horns, significant haemorrhage in large horns
  • Often less blood with wiring
47
Q

Describe methods for haemostasis during dehorning of cattle

A
  • Grasp and pull or twist artery slowly with haemostats so they break below bone line and clot (impossible in some cases)
  • Work around wound circumferentially with hot iron
  • Apply tourniquet around base of horns and poll with baler twine or bands (must be removed after a few days)
48
Q

Describe the after care following dehorning

A
  • Treat with oxytetracycline spray
  • Return to clean environment
  • Advise client to check regularly in first 24 hours
  • Stress minimised
  • Feed from floor not rack to minimise debris into frontal sinus
49
Q

Outline some common problems and complications that occur as a result of dehorning of adult cattle

A
  • Haemorrhage
  • Infection at surgical site (rarely significant problem, manage same as any superficial infection)
  • Sinusitis (foreign material into sinuses, some may require systemic treatment and potential trephination of sinus)
  • Fly strike
50
Q

Where should ear tags be placed in cattle?

A
  • Between the 2 cartilage ribs that run length of ear
  • In middle third of ear
  • Metal tags on proximal border of ear in its middle third
51
Q

What information is given by the primary and management ear tags?

A
  • Primary: identifies animal, herd, country of origin

- Management: identifies bull and dam of cow and DOB, handwritten, can be coloured

52
Q

What are common problems associated with ear tags in cattle?

A
  • Infection

- Trauma

53
Q

Outline the treatment of infection at ear tag sites in cattle

A
  • Lance, clean with antibacterial washes
  • Apply topical antibiotics e.g oxytetracycline spray
  • In bad cases administer broad spec antibiotics
  • Remove tag in severe cases
54
Q

Outline the treatment for trauma at ear tag sites in cattle

A
  • Often not necessary
  • Clean with antibacterials
  • Clamp/tie off vessels, compress with bandage
  • treat infection
  • Surgical repair possible for aesthetic purposes but not required
55
Q

Outline the procedure for cosmetic dehorning

A
  • Rare
  • GA or sedation + local
  • Aseptic prep and procedure
  • Clip and clean
  • Incise and reflect skin around horns
  • Dehorn and close skin with sutures to achieve primary healing
56
Q

Outline the procedure for dehorning goats

A
  • Disbudding kids more complicated than calves
  • Use GA - ketamine + NSAID
  • Remove bud using forceps once cut awau rather than scoop out with disbudding iron
57
Q

Why is disbudding kids more risky than disbudding calves?

A
  • Skulls more fragile

- Higher risk of thermal injury to brain

58
Q

When is it best to nose-ring bulls?

A

Between 6-12 months

59
Q

Outline the requirements regarding nose ringing bulls

A
  • Ideal in all adult bulls to aid safe handling

- Legal requirement for all bulls on public footpaths

60
Q

Outline the restraint for nose ringing bulls

A
  • Crush or suitable stanchion
  • Halter +/- nose tongs
  • Light sedation with xylazine/detomidine for fractious animals
  • Heavy sedation with same in very fractious animals
  • Good restraint needed, high risk of being hit by poll
61
Q

Describe the anaesthesia use for nose ringing bulls

A
  • Local infiltration of septum with procaine theoretically possible but practically difficult
  • May not need local anaesthetic if smooth quick administration
  • Can soak cotton wool in procaine and hold against septum, but takes long time
62
Q

Identify the techniques for nose ringing cattle

A
  • Ring placed through soft tissue of nasal septum in front of cartilage
  • Nose punch to cut out circular punch of tissue
  • Sharp end of ring driven through septum by hand
  • Sharp end of ring driven through septum using specific applicator
  • Scalpel blade 11 used to cut slit through which ring is passed
63
Q

Outline the post-nose-ring application requirements

A
  • Must allow to heal before ring is used to restrain the animal
  • Should not be used as main method for tying up bull
  • If ring is ripped out and cannot be replaced, can stitch up or allow to heal by secondary intention, but cannot be kept on public footpath

Dermatology 2 (23 decks)

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