Lameness in sheep Flashcards
Is lameness in sheep more commonly infectious or non-infectious?
- infectious
Relevance of lameness to sheep industry
- welfare: lameness is painful
- detrimental effects on BW and lamb growth rates
- costs: annually in the UK:
– for flocks with 10% or more lame sheep, footrot losses alone equate to £6.35/ewe/year
– losses for flocks with 5% or less lameness are £3.90/ewe/year
– estimated to cost the sheep industry £80M/year - AMU: estimated that 75% of prescribed antibiotics to sheep flocks is for lameness
Lameness prevalence
- farmer reported in 2020: ~3.2%
- currently on downwards trajectory
- on individual farm it’s estimated that reducing prevalence to the target of 2% will save on average £10/ewe put to the ram
What are the costs of lameness?
- treatment costs: labour, medicines, etc
- production costs: lower BCS, lower conception rate, lower lambing %, poorer lamb condition at birth, poor lamb survival, higher feed & management costs, fewer lambs sold finished, poor ewe survival
Lameness scoring in sheep
0 = sound, bears weight evenly on all 4 feet and walks with an even rhythm
1 = mildly lame, steps are uneven but its not clear which limb(s) is affected
2 = moderately lame, steps are uneven and the stride may be shortened, the affected limb(s) is identifiable
3 = severely lame, mobility is severely compromised such that the sheep frequently stops walking or lies down due to obvious discomfort, the affected limb(s) is clearly identifiable and may be NWB
Causes of lameness
- scald/strip/interdigital dermatitis
- footrot
- CODD
- toe granuloma
- white line dz
- foot abscess
Interdigital dermatitis clinical signs
- inflammation of skin between the claws
- reddening
- paste
- white/grey scum
- distinctive smell
Footrot clinical signs
- smell
- grey ooze
- under running of hoof horn near to skin between claws (gap between the coronary band and at the top of the hoof)
- under-running of horn anywhere (but starts inter-digitally)
Footrot
- commonest cause of lameness
- Dichelobacter nodosus present on 97% of farms
- scald develops into footrot
Fusobacterium necrophorum or Dicheloacter nodosus
D nodosus:
- found in all sheep (lesions or not)
- significantly more prevalent in diseased sheep
- significantly more in feet with ID than FR
- load higher in feet with ID a week before and during episode
- higher load associated with development of FR a week later
F necrophorum:
- found in all sheep
- more frequently detected in diseased sheep
- load relatively stable irrespective of disease state
- higher load once lesion present, but not before - suggestive of a possible opportunistic, rather than causative role
CODD
= contagious ovine digital dermatitis
- highly invasive and painful starting with a lesion at coronary band
- rapid invasion and under running of hoof wall (but starting at the coronary band not the interdigital space as with FR)
- may be no involvement of interdigital space
- often >30% of flock in 1st year and then settles to ~2% lame sheep (as degree of immunity develops)
- many control approaches the same as footrot
- spirochaetes/treponemes involved but often mixed infection with D nodosus
- requires long acting injectable AB - amoxicillin, oxytet (TMPS likely to struggle with the amount of debris/pus present), macrolide if poor response to amoxicillin or oxytet
- individual sheep tx, treat as promptly as possible i.e. within 3d of identifying them as lame
- quarantine important, introduction linked to poor biosecurity
- tooth bathing doesnt provide as good control as parenteral AB of individual sheep
- foot trimming the flock more than 2x yearly associated with higher levels of CODD
Factors linked to lower CODD levels
- not purchasing sheep
- isolating sheep returning to farm
- avoiding use of summer grazing away from farm
- preventing ewes from mixing with neighbouring flocks
- examining feet prior to purchase
- use of footvax? vaccine for FR, unsure whether the vaccine or management of the farms in the study for foot dz that made the difference
Toe granuloma
- inflamed granulomatous tissue coming out from under horn
- from snipping into sensitive part of toe or chronic unresolved footrot
- very difficult to treat
- don’t cut it off without a tourniquet or it will bleed profusely
- use local anaesthetic
- often a result of over trimming the hoof
- warn farmer that might recur
- can cauterise the granuloma site with a hot iron and pack with copper sulphate crystals
White line dz
- defect on abaxial solar surface of horn at junction of wall and sole
- 2 distinct presentations: shelly hoof, toe abscess
Shelly hoof
- soil or debris accumulates laterally at white line
- seen as black half moon if paired away
- often causes no lameness
- however, may lead to acute lameness if pus forms and damage and inflammation affects deeper laminae
