Lameness Flashcards
Key points for nutrition for a health skeleton and gait
Key nutrition in the pathway for bone development and growth
Typical problem with over nutrition (excess ME)
General problems with under nutrition
* Rib fractures in lams– up to 75% of lambs affected
* Aetiology is through to be associated with copper deficiency which impedes the formation of collagen matrices in especially cancellous bone, but also results in thin cortices in long bones
** the resulting weak bone structure goes unnoticed until lambs are slaughtered where it is detected as calluses primarily in ribs but occasionally affects pelvic and long bones as well
** aetiological associations: decreased copper supplementation, increased use of molybdenum in fertilizer mixes causing a relative reduction in copper availability, wet conditions and/or an increase in grass dominance on pastures leading to more abundant molybdenum, soil factors such as high iron/calcium/sulphur tying up copper and possible impact of increased use of mechanical sheep handlers
Problem with all meat and all grain diets?
Ca: Phosphorous ratio
** feed that to a young sheep– improper growth and mineralization of bones
Even if there are no clinical bone abnormalities, poor skeletal growth can also?
* prolong time to reach sale weight or puberty
* increase risk of dystocia (due to small frame size)
* increased risk of hypocalcaemia at lambing
So how do you avoid osteoporosis?
What is important with nutrition during cartilage precursor, osteoblast infiltration, and osteoid production?
What is key during osteoid production, cartilage and osteoid mineralisation and cortical and trabecular bone remodelling in regards to nutrition?
High serum phosphate from a diet high in cereal grains in growing cattle and sheep does what?
Antagonises serum Ca2+–> Low Ca2+ stimulates PTH–> Ca resorbed from the bone–> tends to cause osteoporosis in sheep and cattle
How can we assess secondary nutritional hyperparathyroidism?
* Urinary P excretion… compare urein: serum % of phosphorous and creatinine (baseline metabolite that the kidney doesn’t reabsorb)
What can happen with low dietary vitamin D?
Vitamin D needed for active Ca & P absorption from gut–> low Ca &/0r P means bone can’t be mineralised–> Rickets in growing animals or Osteomalacia in adults (remodelled bone is soft)
How do you ensure enough vitamin D in a ruminants diet?
Avoid rachitogenic factors (anti vit D) and high NH4 (antagonises dietary Ca absorption) e.g. in oat crops
** can give oral or injectable supplements in young sheep if signs are developing to help in situations of Ca deficiency
* Vit D toxicity causes abnormal tissue mineralization
What can happen in oat crop grazing ruminants that are receiving supplemental oats?
TX: Changed their feed to lucerne hay
Keys in a ruminants diet?
* Enough energy, protein, Ca, sunlight, Cu
* Parasitism can have a big effect
* Ca: P balance especially with cereal supplements
How much calcium do you need to add to a diet to fix Ca:P ratio?
How can nutrition affect lameness?
Footrot
* Contagious
* Dichelobacter nodosus
* Numerous strains can affect sheep at any time
* Bacteria live no more than seven days off sheep in all conditions
3 major Factors of the expression of footrot
* footrot spreads when wet
* footrot lesions can progress when dry; a lot of self cure when dry
What species can be infected with footrot? Which strains?
* Sheep: all strains
* Goats: all strains but benign looks virulent and virulent looks benign
* Cattle: benign long term, virulent short term in wet conditions
What conditions must be met for transmission of footrot?
* Interdigital skin must be disrupted- wet conditions water maceration, mixed bacterial flora, unlikely to spread in dry conditions
* Environmental conditions- wet, temp > 10 C, observe underrun in lambs when conditions are frosty
Costs of footrot
* Direct: 10% loss of clean fleece weight; 0.5 micron reduction in fibre diameter, 10% reduction in staple strength; 4-5% loss of fleece value; 12% loss of body weight
* Secondary coss: supplementary feeding due to lower body weight and lower ewe fertility, poorer quality lambs (weaner illthrift, higher death rate, prime lambs lower body weight at sale); metabolic diseases- preg tox; flystrike susceptibility- direct cost due to feet and sitting down, increased risk due to high fly population
Diagnosis of footrot
* Takes 5 minutes to diagnose but can take > 12 months to confirm
* Diagnostic choices:
- not footrot, benign footrot (<1% of sheep with score 4 lesions), virulent footrot (> 1% with score 4 lesions), intermediate footrot (can be difficult making a diagnosis)
Footrot history
* Age, breed etc (Merino more susceptible)
* Previous footrot history
* Recent introductions (last 3 years)
* Recent treatment e.g. footbath (may mask clinical expression)
* Pasture conditions (especially last 6 weeks)
Diagnosis of footrot
* Based on clinical expression
- inspect individual sheep
- inspect 20-30 sheep- if not sure then
- inspect 100 plus sheep at random and foot score
- progression test inspect and re-inspect at intervals of 2-4 weeks during spring
* Smear to show presence of bacteria? Of no real value
* Laboratory tools are of secondary importance
Laboratory tests for footrot
Normal foot
Score 1
Score 2
Score 3a
Score 3b
Score 3c
Score 4
score 5
Chronic score 4/5
Score 4/5
Factors affecting clinical expression
What will you see with benign footrot? Eradication?
* Mild signs most years
* Few signs in dry years
* Very few score 4
* Lots of score 1-2 lesions
* Self cure in dry period
* Back next wet period
* Not obligated to eradicate
* Eradication not cost effective or likely- true carrier state more likely?
* Big decision with borderline strains
* Control options: simple footbathing as necessary
What will you see with virulent footrot?
* Needs suitable weather
* Initially signs similar to benign
* Keeps progressing
* Some self cure
* Obligated to eradicate + it can be eradicated
* Cost effective to eradicate
When do you see footrot? When do you eradicate?
* Spread period: warm most weather, mostly spring/autumn, less in winter except in north, summer requires summer rain
** this is when footrot should be controlled
* Should be eradicated when it is dry unless you destock the farm (usually summer)
Eradication of footrot
* Planning- labour, fencing (eliminate source), infrastructure (foot baths, laneways, inspection equipment), sheep (replacement sheep, stock numbers), budget (cost benefit, cash flow, peak debt)
* Control (winter- spring… control, prepare for first inspection)
* Eradication- summer
* Surveillance- late autumn
* Prevention
Control options
* Footbathing- benign, virulent
- walk through 8m + (formalin, 10% zinc sulphate weekly); stand in 10-20% zinc sulphate, footrite, radicate 12-16 days
* Vaccination- with more virulent strains
* Do nothing- most common but not a good option
Footbathing for footrot- types? frequency?
Footbathing- benign, virulent
- walk through 8m + (formalin, 10% zinc sulphate weekly); stand in 10-20% zinc sulphate, footrite, radicate 12-16 days
** Lambs respond better than chronic adult lesions
Is vaccine available in Australia? How long is the protection? How good is the protection?
Additional doses in high rainfall regions
** Ideally would have combo of footbathing and vaccination
BUT: there is a view that vaccination is “hiding” the disease, many wouldn’t use anyway because give one dose and say it failed due to expectations… not even available in AUS
** Mono/bivalent vaccine more efficacy than multivlaent but not available
So how do you actually eradicate in Australia?
** when it is dry
* By inspection: e.g. 4 inspections throughout summer gradually finding all of the sheep and removing from the flock
* By destocking- change over cost- depends on year, old sheep, poor genotype, change enterprise, disease free source (OJD, lice, drench resistance)
* Only after planning and elimination of potential reintroduction
If you want to salvage sheep with footrot, how ?
Prevention of footrot
Management?
Toe abscess: often associated with shelly toe various pyogenic bacterium
* Foot/heel abscess: Fusobacterium necrophorum
* Risk factors:
- wet muddy conditions, heavy late pregnant ewes or rams
- breeds: merino, crossbred
- older sheep more vulnerable
Common foot conditions of sheep and associated pathogens
Treatment and Prevention of foot conditions
Lame sheep with a history of grain feeding/ change ration, possible DDX?
Arthritis in sheep caused by what pathogens? Pathogenesis?
* Chlamydophila
* Erysipelothrix rhusiopathiae
* Purulent arthritis (such as joint ill) caused by various bacterium:
- Actinomyces pyogenes
- Fusobacterium necrophorus
- Histophilus ovis
- Staph sp., Strep sp.
Caprine Arthritis Encephalitis Virus (CAEV)
* Notifiable
* Lentivirus- related to maedi-visna/ovine progressive pneumonia virus (infects goats– sheep experimentally)
* Incubation months- years
* Low circulating Ab when finally seroconverts– levels provide no immunity and not indicative of presence or absence of infection
* Clinically: Arthritis (big knee)– non suppurative inflammation, especially the carpus and tenosynovitis, hard udder, chronic interstitial pneumonia, chronic weight loss, leukoencephalo-myelitis
** Diagnosis: Clinical signs, histopath, serology- beware potential poor sensitivity & late seroconversion… ongoing surveillance and monitoring and biosecurity after a herd has been infected
** Control: Prevent transmission, Vertical transmission (prevent colostral transmission and pasteurized goat/cow milk and artificial colostrum only… horizontal– 2 herd system (separate clean and infected adults)…. surveillance– ongoing test and cull program…
What is important to know in the history?
* history of foot rot? foot rot free source or just out of the sale yards? previous environmental conditions? any foot bathing could be masking the signs?
** E Collect history etc
C (4 or 5) & D (2)
D or E depending on the severity of the lesions you’ve found
C
D. Score 3b
F Score 4
B
C Footbath weekly in 10% zinc sulphate
E when conditions dry out (late spring- early summer)– as long as you’ve mended fences to avoid reinfection
Right on the cut off between benign and virulent
** Therefore examine more sheep– put sheep in quarantine– may have to inspect later on
D. Quarantine the sheep and reinspect in spring
* standard perception is 7 days
** D. Until the end of a normal spring period after the sheep have been inspected
B. Laminitis or D Septic arthritis
D. Acute laminitis associated with conditions such as colic or metritis
What is Eskaline?
